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Dietary supplement

Immune Defense Ingredients & Drug Interactions

by MegaFood

Immune Defense label
See full label image
Tablet Or Pill Category: Botanical With Nutrients
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Immune Defense against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

Immune Defense is a dietary supplement by MegaFood with 5 active ingredients. Its ingredients are commonly taken for zinc deficiency, immune support, cold symptoms.Based on those ingredients, 1,126 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Echinacea aerial part extract, Andrographis Aerial Parts Extract, Vitamin C. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Immune Defense by MegaFood

Ask about any prescription or over-the-counter medication and we check it for interactions with Immune Defense by MegaFood — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Immune Defense by MegaFood

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Aug 6, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 5 of its 5 active ingredients.
  • No proprietary blends here — you can verify the dose of every single component.

Immune Defense contains 5 active ingredients. Zinc supports immune function and is effective for zinc deficiency and likely effective for Wilson disease.

Vitamin C is an antioxidant that's effective for vitamin C deficiency and possibly helpful for exercise-related respiratory infections. Andrographis aerial parts extract comes from a traditional herb studied for conditions like ulcerative colitis and sore throat, with possibly effective evidence.

Elderberry is included for its traditional immune-support reputation, though evidence for specific conditions isn't yet established. Echinacea aerial part extract rounds out the formula; like elderberry, it's traditionally used for immune support but lacks established evidence for most conditions.

The tablet also contains inactive ingredients: microcrystalline cellulose, hypromellose, brown rice ferment media, silicon dioxide, stearic acid, and rice protein.

Does it work?

Not established
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Not established

The graded evidence we hold for these ingredients covers different conditions than the ones this product is marketed for, so there's no established rating for its stated use.

Why this rating?
  • The label markets this product for: immune system support and defense.
  • We looked for evidence on: Common cold, Influenza, Upper respiratory infections.
  • The closest evidence on file: Andrographis is rated "Insufficient Reliable Evidence To Rate" for Influenza (Natural Medicines).
  • Also on file: Echinacea is rated "Insufficient Reliable Evidence To Rate" for Influenza.

Zinc in this product is effective for preventing or treating zinc deficiency and likely effective for Wilson disease. It's possibly effective for acne, acrodermatitis enteropathica (a rare genetic condition), age-related macular degeneration, and diabetes, though the evidence is limited.

Vitamin C is effective for vitamin C deficiency and possibly effective for anemia in chronic disease, cataracts, and respiratory infections triggered by exercise. Evidence isn't established in our data for andrographis for familial Mediterranean fever, or for elderberry and echinacea for the conditions they're traditionally used for—allergies, lung health, cognitive function, and fatigue—so we can't claim they work for those purposes based on the facts we hold.

The evidence, ingredient by ingredient Zinc Vitamin C Andrographis Elderberry Echinacea

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 5 of the 5 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 5 of 5.
  • General safety write-ups exist for 5 of 5.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Zinc is generally well tolerated in recommended amounts but can cause nausea, diarrhea, metallic taste, and abdominal cramps at higher doses; the safe upper limit for adults is 40 mg daily. Very high doses raise theoretical concern for copper deficiency over time.

Vitamin C is generally safe at normal supplement doses but can trigger nausea, heartburn, diarrhea, and headache above 2 grams daily; people prone to kidney stones should be cautious. Andrographis is often well tolerated short-term but carries theoretical pregnancy concerns and insufficient safety data for breastfeeding; it's best avoided in both.

Elderberry from properly cooked fruit is generally well tolerated, but raw or unripe berries and plant parts contain toxins and should be avoided; insufficient data exists for pregnancy and breastfeeding. Echinacea may trigger allergic reactions, especially in people sensitive to ragweed and related plants; it's best avoided in pregnancy and breastfeeding due to limited safety data.

Side effects, ingredient by ingredient Zinc Vitamin C Andrographis Elderberry Echinacea

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 5 of the 5 matched ingredients can interact with medications — Elderberry, Andrographis, Echinacea, Zinc, Vitamin C.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; immunosuppressants / transplant drugs; cancer treatments.
  • For scale: 1,127 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before taking this product, double-check these medication types with your doctor or pharmacist: blood thinners and antiplatelet drugs (warfarin, aspirin, clopidogrel) due to increased bleeding risk; antibiotics, especially quinolones, tetracyclines, and cephalosporins, which may lose effectiveness; HIV medications including ritonavir and integrase inhibitors; thyroid medication (levothyroxine); oral contraceptives and hormone replacement therapy; and immunosuppressants. Altogether, these interactions span 1,127 individual medications.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with no established evidence rating for its marketed use. Moderate medication interactions have been identified, and safety information is well characterized.

This formula is built around traditional immune-support ingredients with some solid evidence (zinc for deficiency, vitamin C for general antioxidant support) and others with limited or unclear effectiveness for most conditions. If you take antibiotics, blood thinners, HIV medications, thyroid drugs, birth control, or immunosuppressants, check with your doctor or pharmacist before using it—the zinc and other ingredients can interfere with how these drugs work.

For most people without those medications, the ingredients are generally well tolerated in recommended doses, though high intakes should be avoided without medical guidance.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 5 of 5 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Jun 22, 2023.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Immune Defense, straight from the product label.

Brand MegaFood
Barcode (UPC) 051494103661
Net contents 30 Tablet(s)
Market status On market
Date entered into DSLD Jun 22, 2023
DSLD ID 287373
Product type Botanical With Nutrients
Supplement form Tablet Or Pill
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Vegan, Vegetarian, Adult (18 - 50 Years), Kosher, Gluten Free, Dairy Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Immune Defense by MegaFood, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
2 Tablet(s)
Maximum serving Sizes:
2 Tablet(s)
Servings per container
15
UPC/BARCODE
051494103661
IngredientAmount% DV
Zinc5 mg45%
Vitamin C250 mg278%
Andrographis Aerial Parts Extract100 mg--
Elderberry600 mg--
Echinacea aerial part extract500 mg--

Other ingredients: Microcrystalline Cellulose, Hypromellose, Brown Rice, Ferment Media, Silicon Dioxide, Stearic Acid, Rice Protein

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
General Statements

To learn about our seals, please visit megafood.com/standards.

Satisfaction guaranteed or your money back. We believe that the most nutritious food comes from healthy soils and valued farmers. Our goal is to work with farmers who share our commitment to organic and regenerative agriculture. megafood.com/farmers

Seals/Symbols

Non GMO Project Verified nongmoproject.org Certified Vegan Vegan.org Certified NSF Gluten-free OK (Kosher) Glyphosate Residue free detoxproject.org Certified B Corporation

Formulation

Non GMO Project Verified nongmoproject.org Certified NSF Gluten-free Dairy free Soy free Tested 125+ No pesticides & herbicides Glyphosate Residue free detoxproject.org

Certified Vegan Vegan.org

5-Day intense wellness plan

We believe that the most nutritious food comes from healthy soils and valued farmers. Our goal is to work with farmers who share our commitment to organic and regenerative agriculture. megafood.com/farmers

Formula

OK (Kosher)

Immune Defense with oranges, elderberries, echinacea & andrographis

Immune Defense supports immune health when you need it most. It's made vitamin C, zinc and elderberry, plus echinacea and andrographis - bitter herbs known to support immune health. This MegaFood product is made with real food, wholesome nutritional yeast and added nutrients. This vitamin is paired with a whole food in our unique process.

FDA Disclaimer Statement

This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

Brand IP Statement(s)

MegaFood Fresh from farm to tablet

FDA Statement of Identity

Dietary Supplement

Suggested/Recommended/Usage/Directions

Suggested use: 2 tablets 3 times a day with a beverage for 5 days. May be taken anytime throughout the day, even on an empty stomach.

Precautions

Do not exceed 1 bottle every 14 days.

If pregnant, nursing, or you have a health condition, consult your healthcare practitioner before taking this product.

Keep out of reach of children.

Storage

Store tightly sealed in a cool place and avoid exposure to moisture. Once open, consume within three months.

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Immune Defense by MegaFood label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Immune Defense label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Immune Defense by MegaFood

These are the 5 active ingredients this product is made of. Select any to open its full monograph.

Serving size2 Tablet(s) Dosage formTablet Or Pill Servings per container15 Amounts shown are per serving.

Most supplement products combine several ingredients, and a medication can interact with the product through any one of them. Each ingredient below shows whether it has known drug interactions.

Zinc

Interacts with
67 drugs
5 mg per serving Form: Zinc Bisglycinate

Zinc is an essential mineral that your body needs for immune function, wound healing, taste, and smell. Most people get enough from food, but suppleme...

Zinc monograph & interactions

Vitamin C

Interacts with
207 drugs
250 mg per serving Form: organic Orange

Vitamin C (ascorbic acid) is an essential nutrient your body needs but cannot make, so you must get it from food or supplements. It's important for im...

Vitamin C monograph & interactions

Andrographis Aerial Parts Extract

Interacts with
413 drugs
100 mg per serving

Andrographis is a bitter Asian herb traditionally used for colds, flu, and infections, and some studies suggest it may ease cold symptoms and shorten...

Andrographis Aerial Parts Extract monograph & interactions

Elderberry

Interacts with
121 drugs
600 mg per serving

Elderberry is a popular herbal supplement, mainly taken to help with colds and flu. Some small studies suggest it may modestly shorten cold or flu sym...

Elderberry monograph & interactions

Echinacea aerial part extract

Interacts with
816 drugs
500 mg per serving

Echinacea is a popular herb taken to help prevent or shorten the common cold, but study results are mixed and the overall benefit appears small at bes...

Echinacea aerial part extract monograph & interactions

Other (inactive) ingredients: Microcrystalline Cellulose, Hypromellose, Brown Rice, Ferment Media, Silicon Dioxide, Stearic Acid, Rice Protein. These complete the product’s ingredient list but are not active constituents.

Interaction report

Immune Defense by MegaFood Drug Interactions

Want to check YOUR meds against Immune Defense?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
1,126Drugs
1,116 Moderate 10 Minor

Ingredients driving the most interactions

Echinacea aerial part extract 816
Andrographis Aerial Parts Extract 413
Vitamin C 207
Elderberry 121
Zinc 67

Individual Drug Interactions

The ingredients in Immune Defense interact with 1,126 drugs. Click any drug to see the details.

5 of the 5 ingredients in Immune Defense interact with drugs. Each result below shows which ingredient is responsible. Echinacea aerial part extract Andrographis Aerial Parts Extract Vitamin C Elderberry Zinc

Each ingredient & the kinds of drugs it affects

For each ingredient in Immune Defense with known interactions, here are the types of medications they can affect. Open any type for the detail — or search your exact drug in the checker above.

Echinacea aerial part extract12 drug types · 816 drugs

Caffeine

Echinacea can increase plasma levels of caffeine by inhibiting its metabolism.
Echinacea seems to increase plasma concentrations of caffeine by around 30%. This is likely due to inhibition of cytochrome P450 1A2 (CYP1A2) by echinacea.

Likelihood Probable Evidence B
Cytochrome P450 1A2 (Cyp1A2) Substrates

Echinacea might inhibit the metabolism of CYP1A2 and increase plasma levels of some drugs.
Echinacea appears to inhibit CYP1A2 enzymes in humans. Additionally, echinacea seems to increase plasma concentrations of caffeine, a CYP1A2 substrate, by around 30%. Theoretically, echinacea might increase levels of other drugs metabolized by CYP1A2.

Likelihood Possible Evidence B
Cytochrome P450 3A4 (Cyp3A4) Substrates

Echinacea may induce hepatic CYP3A4 and inhibit intestinal CYP3A4. This may increase or decrease levels of drugs metabolized by CYP3A4.
Several clinical trials have shown that taking echinacea for up to one month does not significantly affect the metabolism of various CYP3A4 substrates, including midazolam, docetaxel, etravirine, lopinavir-ritonavir, and darunavir-ritonavir. However, other clinical research shows that echinacea may increase the clearance of midazolam, suggesting that echinacea might induce CYP3A4. The discrepancy is thought to be due to differing effects of echinacea on intestinal versus hepatic CYP3A4 enzymes. Echinacea appears to induce hepatic CYP3A4 but inhibit intestinal CYP3A4. In some cases, these effects might cancel each other out, but in others, drug levels may be increased or decreased depending on the level of effect at hepatic and intestinal sites. The effect of echinacea on CYP3A4 activity may differ depending on the CYP3A4 substrate.

Likelihood Possible Evidence B
Etoposide (Vepesid)

Echinacea may increase levels of etoposide.
In one report, concomitant use of etoposide and echinacea was associated with more severe thrombocytopenia than the use of etoposide alone, suggesting inhibition of etoposide metabolism. Etoposide is a cytochrome P450 3A4 (CYP3A4) substrate. Echinacea has variable effects on CYP3A4, but some studies have reported inhibition of the enzyme.

Likelihood Possible Evidence D
Immunosuppressants

Echinacea has immunostimulant activity which may interfere with immunosuppressant therapy.
Theoretically, echinacea may interfere with immunosuppressant therapy because of its immunostimulant activity.

Likelihood Possible Evidence B
Darunavir (Prezista)

Theoretically, echinacea may interfere with the metabolism of darunavir; however, a small clinical study found no effect.
Darunavir is metabolized by cytochrome P450 3A4 (CYP3A4) and is administered with the CYP3A4 inhibitor ritonavir to increase its plasma concentrations. Echinacea has variable effects on CYP3A4, but administration of an E. purpurea root extract (Arkocapsulas Echinacea, Arkopharma) 500 mg four times daily for 14 days did not affect darunavir/ritonavir pharmacokinetics in 15 HIV-infected patients.

Likelihood Unlikely Evidence B
Dayquil Severe

Echinacea is reported to have varying effects on a number of Cytochrome P450 metabolizing enzymes in the liver, including CYP1A2 and CYP3A4, which play a role in acetaminophen and dextromethorphan metabolism (both contained in DayQuil Severe), respectively. Studies have reported both enzyme inhibition and induction, making it difficult to predict clinically significant drug interactions with reliability. Specific drug interaction studies reporting definitive results are rare, and potential drug interactions involving echinacea should likely be taken on a case-by-case basis. Based on what we know about how acetaminophen and dextromethorphan are metabolized, the risk of a clinically significant interaction between echinacea and DayQuil Severe is low.

Likelihood Unlikely Evidence A
Docetaxel (Taxotere)

Theoretically, echinacea may interfere with the metabolism of docetaxel; however, a small clinical study found no effect.
Docetaxel is metabolized by cytochrome P450 3A4 (CYP3A4). Echinacea has variable effects on CYP3A4, but taking E. purpurea whole plant extract (Echinaforce, A. Vogel Biopharma AG) 20 drops three times daily for 2 weeks did not alter the pharmacokinetics of docetaxel in one clinical study.

Likelihood Unlikely Evidence B
Etravirine (Intelence)

Theoretically, echinacea may interfere with the metabolism of etravirine; however, a small clinical study found no effect.
Etravirine is metabolized by cytochrome P450 3A4 (CYP3A4). Echinacea has variable effects on CYP3A4, but taking E. purpurea root extract (Arkocapsulas Echinacea, Arkopharma) 500 mg three times daily for 14 days did not alter the pharmacokinetics of etravirine in HIV-infected patients.

Likelihood Unlikely Evidence B
Lopinavir/Ritonavir (Kaletra)

Theoretically, echinacea may interfere with the metabolism of lopinavir; however, a small clinical study found no effect.
Lopinavir is metabolized by cytochrome P450 3A4 (CYP3A4) and is administered with the CYP3A4 inhibitor ritonavir to increase its plasma concentrations. Echinacea has variable effects on CYP3A4, but taking E. purpurea (Echinamide, Natural Factors Nutritional Products, Inc.) 500 mg three times daily for 14 days did not alter the pharmacokinetics of lopinavir/ritonavir in healthy volunteers.

Likelihood Unlikely Evidence B
Midazolam (Versed)

Theoretically, echinacea may increase the metabolism of intravenous midazolam.
Echinacea induces hepatic CYP3A4 and might decrease plasma levels of midazolam by about 20%, reducing the effectiveness of intravenous midazolam. Echinacea also appears to inhibit intestinal CYP3A4, which could theoretically increase the bioavailability of oral midazolam. This may cancel out the decrease in availability caused by induction of hepatic CYP3A4, such that overall plasma levels after oral administration of midazolam are not affected by echinacea.

Likelihood Possible Evidence B
Warfarin (Coumadin)

Echinacea seems to increase the clearance of warfarin, although the effect may not be clinically significant.
Preliminary clinical research in healthy male volunteers suggests that taking echinacea increases the clearance of the active S-isomer of warfarin after a single dose of warfarin, but there was not a clinically significant effect on the INR.

Likelihood Possible Evidence B
Echinacea aerial part extract full monograph & interactions

Andrographis Aerial Parts Extract6 drug types · 413 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, andrographis might increase the risk of bleeding when used with anticoagulant or antiplatelet drugs.
Animal and laboratory studies suggest that andrographis has antiplatelet effects.

Likelihood Possible Evidence D
Antihypertensive Drugs

Theoretically, andrographis might increase the risk of hypotension when used with antihypertensive drugs.
Animal research suggests that andrographis has hypotensive effects.

Likelihood Possible Evidence D
Immunosuppressants

Theoretically, andrographis might interfere with the effects of immunosuppressive drugs.
Laboratory research suggests that andrographolide has immunostimulant activity.

Likelihood Possible Evidence D
Celecoxib (Celebrex)

Theoretically, andrographis extract might increase the maximum concentration and time to peak concentration of celecoxib. The clinical significance of these changes is unclear.
Animal research suggests that andrographis extract taken orally increases the maximum concentration and time to peak concentration of celecoxib but does not appear to impact the area under the curve.

Likelihood Possible Evidence D
Etoricoxib (Arcoxia)

Theoretically, andrographis might decrease the absorption of etoricoxib, although the clinical significance is unclear.
Animal research shows that andrographis extract, or the constituent andrographolide, taken orally with etoricoxib decreases the bioavailability of etoricoxib. However, this reduced bioavailability is not correlated with a reduction in the anti-inflammatory effects of etoricoxib in arthritic mice models. The clinical significance of this interaction is unclear.

Likelihood Possible Evidence D
Glipizide (Glucotrol)

Theoretically, andrographis extract might increase the maximum concentration and area under the curve of glipizide; however, opposite effects are seen with the constituent, andrographolide. The clinical significance of this interaction is unclear.
Animal research suggests that andrographis extract taken orally with glipizide in diabetes-induced rats increases the maximum concentration and area under the curve of glipizide. However, the opposite effect is seen with the constituent, andrographolide, in which the maximum concentration and area under the curve are decreased when taken with glipizide.

Likelihood Possible Evidence D
Andrographis Aerial Parts Extract full monograph & interactions

Vitamin C13 drug types · 207 drugs

Alkylating Agents

Theoretically, antioxidant effects of vitamin C might reduce the effectiveness of alkylating agents.
The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs that generate free radicals, such as cyclophosphamide, chlorambucil, carmustine, busulfan, and thiotepa. In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells. More evidence is needed to determine what effect, if any, antioxidants such as vitamin C have on chemotherapy.

Likelihood Possible Evidence D
Aluminum

Vitamin C can increase the amount of aluminum absorbed from aluminum compounds.
Research in animals and humans shows that vitamin C increases aluminum absorption, theoretically by chelating aluminum and keeping it in solution where it is available for absorption. In people with normal renal function, urinary excretion of aluminum will likely increase, making aluminum retention and toxicity unlikely. Patients with renal failure who take aluminum-containing compounds such as phosphate binders should avoid vitamin C supplements in doses above the recommended dietary allowances.

Likelihood Probable Evidence B
Antitumor Antibiotics

Theoretically, the antioxidant effects of vitamin C might reduce the effectiveness of antitumor antibiotics.
The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs which generate free radicals, such as doxorubicin. In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells. More evidence is needed to determine what effects, if any, antioxidants such as vitamin C have on chemotherapy.

Likelihood Possible Evidence D
Estrogens

Vitamin C might increase blood levels of estrogens.
Increases in plasma estrogen levels of up to 55% occur under some circumstances when vitamin C is taken concurrently with oral contraceptives or hormone replacement therapy, including topical products. It is suggested that vitamin C prevents oxidation of estrogen in the tissues, regenerates oxidized estrogen, and reduces sulfate conjugation of estrogen in the gut wall. When tissue levels of vitamin C are high, these processes are already maximized and supplemental vitamin C does not have any effect on estrogen levels. Increases in plasma estrogen levels may occur when patients who are deficient in vitamin C take supplements. Monitor these patients for estrogen-related side effects.

Likelihood Probable Evidence B
Fluphenazine (Prolixin)

Theoretically, vitamin C might decrease levels of fluphenazine.
In one patient there was a clinically significant decrease in fluphenazine levels when vitamin C (500 mg twice daily) was started. The mechanism is not known, and there is no further data to confirm this interaction.

Likelihood Possible Evidence D
Indinavir (Crixivan)

Vitamin C can modestly reduce indinavir levels.
One pharmacokinetic study shows that taking vitamin C 1 gram orally once daily along with indinavir 800 mg orally three times daily reduces the area under the concentration-time curve of indinavir by 14%. The mechanism of this interaction is unknown, but it is unlikely to be clinically significant in most patients. The effect of higher doses of vitamin C on indinavir levels is unknown.

Likelihood Probable Evidence B
Levothyroxine (Synthroid, Others)

Vitamin C can increase levothyroxine absorption.
Two clinical studies in adults with poorly controlled hypothyroidism show that swallowing levothyroxine with a glass of water containing vitamin C 500-1000 mg in solution reduces thyroid stimulating hormone (TSH) levels and increases thyroxine (T4) levels when compared with taking levothyroxine alone. This suggests that vitamin C increases the oral absorption of levothyroxine, possibly due to a reduction in pH.

Likelihood Probable Evidence B
Warfarin (Coumadin)

High-dose vitamin C might reduce the levels and effectiveness of warfarin.
Vitamin C in high doses may cause diarrhea and possibly reduce warfarin absorption. There are reports of two people who took up to 16 grams daily of vitamin C and had a reduction in prothrombin time. Lower doses of 5-10 grams daily can also reduce warfarin absorption. In many cases, this does not seem to be clinically significant. However, a case of warfarin resistance has been reported for a patient who took vitamin C 500 mg twice daily. Cessation of vitamin C supplementation resulted in a rapid increase in international normalized ratio (INR). Tell patients taking warfarin to avoid taking vitamin C in excessively high doses (greater than 10 grams daily). Lower doses may be safe, but the anticoagulation activity of warfarin should be monitored. Patients who are stabilized on warfarin while taking vitamin C should avoid adjusting vitamin C dosage to prevent the possibility of warfarin resistance.

Likelihood Possible Evidence D
Acetaminophen (Tylenol, Others)

High-dose vitamin C might slightly prolong the clearance of acetaminophen.
A small pharmacokinetic study in healthy volunteers shows that taking high-dose vitamin C (3 grams) 1.5 hours after taking acetaminophen 1 gram slightly increases the apparent half-life of acetaminophen from around 2.3 hours to 3.1 hours. Ascorbic acid competitively inhibits sulfate conjugation of acetaminophen. However, to compensate, elimination of acetaminophen glucuronide and unconjugated acetaminophen increases. This effect is not likely to be clinically significant.

Likelihood Probable Evidence B
Aspirin

Acidification of the urine by vitamin C might increase aspirin levels.
It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels. However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion, suggesting this interaction is not clinically significant.

Likelihood Possible Evidence B
Choline Magnesium Trisalicylate (Trilisate)

Acidification of the urine by vitamin C might increase choline magnesium trisalicylate levels.
It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels. However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion, suggesting this interaction probably is not clinically significant.

Likelihood Possible Evidence B
Niacin

Vitamin C might decrease the beneficial effects of niacin on high-density lipoprotein (HDL) cholesterol levels.
A combination of niacin and simvastatin (Zocor) effectively raises HDL cholesterol levels in patients with coronary disease and low HDL levels. Clinical research shows that taking a combination of antioxidants (vitamin C, vitamin E, beta-carotene, and selenium) along with niacin and simvastatin (Zocor) attenuates this rise in HDL, specifically the HDL-2 and apolipoprotein A1 fractions, by more than 50% in patients with coronary disease. It is not known whether this adverse effect is due to a single antioxidant such as vitamin C, or to the combination. It also is not known whether it will occur in other patient populations.

Likelihood Possible Evidence A
Salsalate (Disalcid)

Acidification of the urine by vitamin C might increase salsalate levels.
It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels. However, short-term use of up to 6 grams/day vitamin C does not seem to affect urinary pH or salicylate excretion, suggesting this interaction probably is not clinically significant.

Likelihood Possible Evidence B
Vitamin C full monograph & interactions

Elderberry2 drug types · 121 drugs

Immunosuppressants

Theoretically, elderberry might interfere with immunosuppressant therapy due to its immunostimulant activity.
Elderberry has immunostimulant activity, increasing the production of cytokines, including interleukin and tumor necrosis factor.

Likelihood Possible Evidence B
Pazopanib (Votrient)

Theoretically, elderberry might interact with pazopanib, potentially increasing the risk of adverse effects.
In one case, a 65-year-old patient taking pazopanib for 4 weeks for soft-tissue sarcoma developed severe nausea, loose stools, and elevated alanine transaminase and aspartate transaminase levels and was diagnosed with grade 3 liver injury. The patient reported taking elderberry supplements for 2 years, dose unspecified, and was also taking a multivitamin and a calcium supplement. The patient's symptoms and liver enzyme levels improved upon discontinuation of pazopanib and all supplements. Pazopanib treatment was re-initiated, at a lower dose, with no further evidence of liver injury. It was unclear in this case report if the elderberry supplements were derived from the berry, the flower, or the combination.

Likelihood Possible Evidence D
Elderberry full monograph & interactions

Zinc10 drug types · 67 drugs

Bictegravir/Emtricitabine/Tenofovir Alafenamide (Biktarvy)

Theoretically, zinc might decrease levels of bictegravir/emtricitabine/tenofovir alafenamide by reducing its absorption.
Advise patients that bictegravir/emtricitabine/tenofovir alafenamide should be taken at least 2 hours before or 6 hours after zinc containing products.

Likelihood Probable Evidence D
Cephalexin (Keflex)

Zinc might decrease cephalexin levels by chelating with cephalexin in the gut and preventing its absorption.
A pharmacokinetic study shows that zinc sulfate 250 mg taken concomitantly with cephalexin 500 mg decreases peak levels of cephalexin by 31% and reduces the exposure to cephalexin by 27%. Also, taking zinc sulfate 3 hours before cephalexin decreases peak levels of cephalexin by 11% and reduces the exposure to cephalexin by 18%. By decreasing cephalexin levels, zinc might increase the risk of treatment failure. This effect does not occur when zinc is taken 3 hours after the cephalexin dose. To avoid an interaction, advise patients take zinc sulfate 3 hours after taking cephalexin.

Likelihood Probable Evidence B
Cisplatin (Platinol-Aq)

Theoretically, zinc might interfere with the therapeutic effects of cisplatin.
Animal research suggests that zinc stimulates tumor cell production of the protein metallothionein, which binds and inactivates cisplatin. It is not known whether zinc supplements or high dietary zinc intake can cause clinically significant interference with cisplatin therapy. Cisplatin might also increase zinc excretion.

Likelihood Possible Evidence D
Integrase Inhibitors

Theoretically, taking zinc along with integrase inhibitors might decrease the levels and clinical effects of these drugs.
Zinc is a divalent cation. Pharmacokinetic studies have shown that other divalent cations such as calcium and iron can decrease blood levels of the integrase inhibitor dolutegravir through chelation.

Likelihood Possible Evidence D
Penicillamine (Cuprimine, Depen)

Zinc might reduce the levels and clinical effects of penicillamine.
By forming an insoluble complex with penicillamine, zinc interferes with penicillamine absorption and activity. Zinc supplements reduce the efficacy of low-dose penicillamine (0.5-1 gram/day), but do not seem to affect higher doses (1-2.75 gram/day), provided dosing times are separated. Advise patients to take zinc and penicillamine at least 2 hours apart.

Likelihood Probable Evidence B
Quinolone Antibiotics

Zinc can decrease the levels and clinical effects of quinolones antibiotics.
Quinolones form complexes with zinc in the gastrointestinal tract, reducing absorption of both the quinolone and zinc if taken at the same time. Advise patients to take these drugs at least 2 hours before, or 4-6 hours after, zinc supplements.

Likelihood Probable Evidence B
Ritonavir (Norvir)

Zinc modestly reduces levels of ritonavir.
Clinical research shows that zinc might reduce serum ritonavir levels by chelating with ritonavir in the gut and preventing its absorption. In patients with HIV, ritonavir is taken with atazanavir to prevent the metabolism and increase the effects of atazanavir. A pharmacokinetic study shows that, in patients being treated with atazanavir/ritonavir, co-administration of zinc sulfate (Solvazinc tablets) 125 mg as a single dose or as multiple daily doses for 2 weeks reduces plasma levels of ritonavir by about 16%. However, atazanavir levels still remains high enough to prevent HIV virus replication. Therefore, the decrease in ritonavir levels is not likely to be clinically significant.

Likelihood Probable Evidence B
Tetracycline Antibiotics

Zinc might reduce levels of tetracycline antibiotics.
Tetracyclines form complexes with zinc in the gastrointestinal tract, which can reduce absorption of both the tetracycline and zinc when taken at the same time. Taking zinc sulfate 200 mg with tetracycline reduces absorption of the antibiotic by 30% to 40%. Demeclocycline and minocycline cause a similar interaction. However, doxycycline does not seem to interact significantly with zinc. Advise patients to take tetracyclines at least 2 hours before, or 4-6 hours after, zinc supplements to avoid any interactions.

Likelihood Probable Evidence B
Amiloride (Midamor)

Amiloride can modestly reduce zinc excretion and increase zinc levels.
Clinical research shows that amiloride can reduce urinary zinc excretion, especially at doses of 10 mg per day or more. This zinc-sparing effect can help to counteract zinc losses caused by thiazide diuretics, but it is unlikely to cause zinc toxicity at usual amiloride doses. The other potassium-sparing diuretics, spironolactone (Aldactone) and triamterene (Dyrenium), do not seem to have a zinc-sparing effect.

Likelihood Probable Evidence B
Atazanavir (Reyataz)

Zinc modestly reduces levels of atazanavir, although this effect does not seem to be clinically significant.
Clinical research shows that zinc might decrease serum atazanavir levels by chelating with atazanavir in the gut and preventing its absorption. Although a single dose of zinc sulfate (Solvazinc tablets) 125 mg orally does not affect atazanavir concentrations in patients being treated with atazanavir/ritonavir, co-administration of zinc sulfate 125 mg daily for 2 weeks reduces plasma levels of atazanavir by about 22% in these patients. However, despite this decrease, atazanavir levels still remain at high enough concentrations for the prevention of HIV virus replication.

Likelihood Probable Evidence B
Zinc full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Immune Defense, from the product label.

MegaFood

See all MegaFood products
Name
MegaFood
Street Address
PO Box 5244
City
Manchester
State
NH
ZipCode
03108
Phone Number
800.848.2542
Web Address
megafood.com
Pharmacist Counseling Corner

Immune Defense by MegaFood: Common Questions

Does Immune Defense by MegaFood interact with any medications?
Yes. Based on its ingredients, Immune Defense has a known interaction with 1,126 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Immune Defense contains 5 active ingredients, and an interaction can come from any of them. We check every ingredient, combine the results into one list per medication, and show which ingredient and mechanism is responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Can I take this if I'm pregnant or breastfeeding?
Zinc and vitamin C are rated likely safe in pregnancy at normal dietary levels, but andrographis is possibly unsafe in pregnancy and should be avoided, and elderberry and echinacea lack enough safety data for either pregnancy or breastfeeding. Talk to your doctor or pharmacist for personalized advice before taking this product.
What's the most common side effect I might notice?
From zinc, you might experience nausea, diarrhea, metallic taste, or abdominal cramps, especially at higher doses. Vitamin C can cause nausea, heartburn, or diarrhea above 2 grams daily. Andrographis may cause nausea, diarrhea, headache, or rash. Echinacea and elderberry can trigger nausea or rash in some people, and echinacea may cause allergic reactions in those sensitive to ragweed.
Does this product actually work for immune support?
Zinc is effective for zinc deficiency; vitamin C is effective for vitamin C deficiency. Andrographis has possibly effective evidence for sore throat and ulcerative colitis. Elderberry and echinacea are traditionally used for immune support and colds, but evidence isn't established in our data for those specific uses.
What is andrographis and why is it in here?
Andrographis is an herb traditionally used in Asia for immune and inflammation support. The extract in this product comes from the above-ground parts of the plant and has possibly effective evidence for conditions like sore throat and ulcerative colitis, though the long-term safety and product quality aren't fully established.
Is there a risk of copper deficiency if I take this long-term?
Very high doses of zinc (well above the safe upper limit of 40 mg daily for adults) taken long-term may interfere with copper absorption and raise the risk of deficiency. Stick to recommended doses, and if you take high-dose zinc under medical supervision, ask your doctor or pharmacist whether you need copper supplementation.
What if I'm allergic to ragweed?
Echinacea in this product may trigger allergic reactions in people sensitive to ragweed and related plants (like chrysanthemums and daisies). If you have a ragweed allergy, talk with your doctor or pharmacist before taking this product.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Immune Defense label
Go deeper

The Full Monographs Behind Immune Defense’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Zinc

Interacts with 67 drugs

Zinc is an essential mineral that your body needs for immune function, wound healing, taste, and smell. Most people get enough from food, but supplements can help correct or prevent a defici...

Read the full Zinc monograph → Herb & supplement monograph

Vitamin C

Interacts with 207 drugs

Vitamin C (ascorbic acid) is an essential nutrient your body needs but cannot make, so you must get it from food or supplements. It's important for immune function, collagen, and acts as an...

Read the full Vitamin C monograph → Herb & supplement monograph

Andrographis

Interacts with 413 drugs

Andrographis is a bitter Asian herb traditionally used for colds, flu, and infections, and some studies suggest it may ease cold symptoms and shorten how long they last. The evidence is limi...

Read the full Andrographis monograph → Herb & supplement monograph

Elderberry

Interacts with 121 drugs

Elderberry is a popular herbal supplement, mainly taken to help with colds and flu. Some small studies suggest it may modestly shorten cold or flu symptoms, but the evidence is limited and n...

Read the full Elderberry monograph → Herb & supplement monograph

Echinacea

Interacts with 816 drugs

Echinacea is a popular herb taken to help prevent or shorten the common cold, but study results are mixed and the overall benefit appears small at best. It is generally well tolerated for sh...

Read the full Echinacea monograph →
Sources

Sources & How We Checked

Immune Defense's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 222 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Zinc 88 references
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  4. Blondeau JM. Expanded activity and utility of the new fluoroquinolones: a review. Clin Ther 1999;21:3-40. PubMed
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  12. Hansten PD, Horn JR. Drug Interactions Analysis and Management. Vancouver, WA: Applied Therapeutics Inc., 1997 and updates.
  13. Seelig MS. Auto-immune complications of D-penicillamine - A possible result of zinc and magnesium depletion and of pyridoxine inactivation. J Am Coll Nutr 1982;1:207-14. PubMed
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  22. Age-Related Eye Disease Study Research Group. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss. AREDS report no. 8. Arch Oph
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  58. Jafek, B. W., Linschoten, M. R., and Murrow, B. W. Anosmia after intranasal zinc gluconate use. Am J Rhinol. 2004;18(3):137-141. DOI
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  88. US Food and Drug Administration (FDA). Biktarvy Prescribing Information. October 2024. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/210251Orig1s020lbl.pdf. Accessed July 16, 2025.

See these in context on the Zinc monograph →

Vitamin C 51 references
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Andrographis 26 references
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Echinacea 51 references
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DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

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