Major interaction on record — check this product against your medications before combining. Check your meds →
Dietary supplement

Vitamin C Ingredients & Drug Interactions

by Isotonix

Vitamin C label
See full label image
Powder Category: Other Combinations
Most serious interaction: Major
Clinical methodology reviewed by · Updated Sep 9, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Vitamin C 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: Major

Vitamin C is a dietary supplement by Isotonix with 3 active ingredients. Its ingredients are commonly taken for eye and vision health, skin health and acne, immune support.Based on those ingredients, 550 medications have a known interaction with it, the most serious rated major. The ingredients most likely to interact are Vitamin A, Vitamin C, Potassium. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Vitamin C by Isotonix

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

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HelloPharmacist Scorecard of Vitamin C by Isotonix

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 Jul 11, 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 3 of its 3 active ingredients.
  • No proprietary blends here — you can verify the dose of every single component.

Isotonix Vitamin C contains three active ingredients: vitamin A, which supports vision and immune function; vitamin C, an antioxidant that plays a role in immune health and collagen formation; and potassium, a mineral essential for heart rhythm and muscle function. The powder also includes several inactive ingredients—fructose, glucose, maltodextrin, malic acid, orange flavor, silica, citric acid, and stearic acid—that serve as sweeteners, thickeners, flavoring, and stabilizers.

Does it work?

Moderate evidence
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
Moderate

Some clinical evidence supports this product's ingredients for its stated purpose, but it isn't conclusive.

Why this rating?
  • The label markets this product for: antioxidant protection and immune support.
  • We looked for evidence on: Cardiovascular disease (CVD), Hypercholesterolemia, Hypertension, Atherosclerosis, Exercise-induced muscle damage, Iron deficiency anemia — and 4 related terms.
  • The strongest evidence on file: Vitamin A is rated "Possibly Effective" for Aging skin (Natural Medicines).
  • Also on file: Vitamin C is rated "Possibly Effective" for Hypercholesterolemia, Hypertension.
  • Also on file: Vitamin C is rated "Possibly Ineffective" for Atherosclerosis, Cardiovascular disease (CVD).

Vitamin A is effective for treating vitamin A deficiency and possibly effective for oral leukoplakia, aging skin, measles, ulcerative colitis, and bronchopulmonary dysplasia. Vitamin C is effective for vitamin C deficiency and possibly effective for anemia of chronic disease, atrial fibrillation, cataracts, and exercise-induced respiratory infections.

The product facts we hold don't include effectiveness data for potassium as a supplement ingredient.

The evidence, ingredient by ingredient Vitamin A Vitamin C Potassium

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 3 of the 3 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 3 of 3.
  • General safety write-ups exist for 3 of 3.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Vitamin A and vitamin C are both generally well-tolerated at recommended amounts, but high doses of both can cause side effects. Vitamin A toxicity—which can happen because it builds up in your body—can cause serious problems including liver damage, headache, and skin issues; very high doses have caused pseudotumor cerebri, coma, and death in rare cases.

Vitamin C at very high doses can cause kidney stones (especially in people prone to them), abdominal cramps, diarrhea, nausea, and vomiting; rare cases of serious kidney damage and other complications have been reported with extremely high doses. Potassium is generally well-tolerated, but high levels can cause serious heart rhythm problems, dangerously low blood pressure, and mental confusion.

In pregnancy, normal dietary amounts of vitamin A and C are fine, but high-dose supplements of both should be avoided—vitamin A high doses can cause birth defects. For potassium, dietary amounts are appropriate in pregnancy, but supplements should only be used under medical guidance.

Breastfeeding: normal amounts of all three are appropriate; high-dose supplements should be avoided unless your doctor directs otherwise.

Side effects, ingredient by ingredient Vitamin A Vitamin C Potassium

Meds to double-check

Major interaction found
Known Interaction Concern · database check
Major identified

At least one ingredient has a documented Major-severity interaction. Check your medications for a personalized result.

Why this rating?
  • 3 of the 3 matched ingredients can interact with medications — Potassium, Vitamin A, Vitamin C.
  • The most serious interaction on file is rated Major.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; cancer treatments.
  • For scale: 551 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 you take this product, check with your pharmacist if you're on retinoids (prescription vitamin A for severe acne), blood thinners like warfarin, tetracycline antibiotics, blood pressure medications (ACE inhibitors, ARBs, or potassium-sparing diuretics), birth control or hormone therapy, chemotherapy, or thyroid medication. These are the main drug types to watch for.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence for its stated purpose. Major medication interactions have been identified, and safety information is well characterized.

This product works best for people who are deficient in these vitamins and need supplementation at recommended doses. If you take any prescription medication—especially blood thinners, blood pressure drugs, birth control, tetracycline antibiotics, or chemotherapy—talk to your pharmacist or doctor before starting this product.

Don't exceed recommended doses; stick to what's on the label unless your clinician tells you otherwise.

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

Assessment coverage: 3 of 3 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Jul 25, 2024.

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 Vitamin C, straight from the product label.

Brand Isotonix
Barcode (UPC) 848570006882
Net contents 3.5 Ounce(s); 100 Gram(s)
Market status On market
Date entered into DSLD Jul 25, 2024
DSLD ID 313416
Product type Other Combinations
Supplement form Powder
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Vegan, Vegetarian, Adult (18 - 50 Years), 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 Vitamin C by Isotonix, 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:
3.3 Gram(s)
Maximum serving Sizes:
3.3 Gram(s)
Servings per container
30
UPC/BARCODE
848570006882
IngredientAmount% DV
Calories10 Calorie(s)--
Total Carbohydrates2 Gram(s)1%
Vitamin A240 mcg RAE27%
Vitamin C500 mg556%
Added Sugars2 Gram(s)4%
Total Sugars2 Gram(s)--
Potassium100 mg2%

Other ingredients: Fructose, Glucose, Maltodextrin, Malic Acid, Orange flavor, Silica, Citric Acid, Stearic Acid

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.
Formulation

Provides antioxidant protection Supports a healthy immune system Promotes skeletal, muscle, cardiovascular and skin health Helps maintain healthy cholesterol levels Promotes normal regulation of heart functions

Maximum absorption occurs when taken on an empty stomach. This product is isotonic only if the specified amounts of powder and water are used.

This vegan product contains no added wheat, soy, yeast, gluten, artificial flavor, salt, preservatives or milk.

Gluten free

Vegan

Brand IP Statement(s)

Isotonix The world's most advanced nutraceuticals

FDA Statement of Identity

An Isotonic-Capable Dietary Supplement

Suggested/Recommended/Usage/Directions

Directions for use: Pour 1 level, white bottle capful of powder into the overcap. Add water to the line on the overcap (2 fl oz/60 mL) and stir. As a dietary supplement, take once daily or as directed by your healthcare provider. Maximum absorption occurs when taken on an empty stomach. This product is isotonic only if the specified amounts of powder and water are used.

Precautions

Warning: If you are currently using prescription drugs, have an ongoing medical condition, or are pregnant or breastfeeding, consult your healthcare provider before using this product.

Keep out of the reach of children.

Do not use if safety seal is broken or missing.

Resale on third-party websites is strictly prohibited unless specifically authorized by Market America or its corporate affiliates. If barcodes are altered or you purchase this product from an unauthorized third-party website, the product is not guaranteed by Market America or its corporate affiliates.

Storage

Store in a cool, dry place.

FDA Disclaimer Statement

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

Seals/Symbols

Vegan

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

See for yourself

Vitamin C by Isotonix label

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

Vitamin C 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 Vitamin C by Isotonix

These are the 3 active ingredients this product is made of. Select any to open its full monograph.

Serving size3.3 Gram(s) Dosage formPowder Servings per container30 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.

Vitamin A

Interacts with
387 drugs
240 mcg RAE per serving Form: Beta-Carotene

Vitamin A is an essential nutrient important for vision, skin, immune function, and growth. Most people get enough from a balanced diet, and supplemen...

Vitamin A monograph & interactions

Vitamin C

Interacts with
207 drugs
500 mg per serving Form: Ascorbic Acid

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

Potassium

Interacts with
62 drugs
100 mg per serving Form: Potassium Bicarbonate

Potassium is an essential mineral your body needs for nerve signals, muscle function, and a steady heartbeat, and most people get enough from a balanc...

Potassium monograph & interactions

Other (inactive) ingredients: Fructose, Glucose, Maltodextrin, Malic Acid, Orange flavor, Silica, Citric Acid, Stearic Acid. These complete the product’s ingredient list but are not active constituents.

Interaction report

Vitamin C by Isotonix Drug Interactions

Want to check YOUR meds against Vitamin C?

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
550Drugs
9 Major 508 Moderate 33 Minor

Ingredients driving the most interactions

Vitamin A 387
Vitamin C 207
Potassium 62

Individual Drug Interactions

The ingredients in Vitamin C interact with 550 drugs. Click any drug to see the details.

3 of the 3 ingredients in Vitamin C interact with drugs. Each result below shows which ingredient is responsible. Vitamin A Vitamin C Potassium

Each ingredient & the kinds of drugs it affects

For each ingredient in Vitamin C 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.

Vitamin A4 drug types · 387 drugs

Retinoids

Concomitant use of retinoids with vitamin A supplements might produce supratherapeutic vitamin A levels.
Retinoids, which are vitamin A derivatives, could have additive toxic effects when taken with vitamin A supplements.

Likelihood Probable Evidence D
Hepatotoxic Drugs

Theoretically, taking high doses of vitamin A in combination with other potentially hepatotoxic drugs might increase the risk of liver disease.
The tolerable upper intake level (UL) is the highest level of intake that is likely to pose no risk of adverse effects. Doses of vitamin A above the UL can cause hepatotoxicity, ranging from elevated liver enzymes to liver failure.

Likelihood Possible Evidence C
Tetracycline Antibiotics

Theoretically, taking tetracycline antibiotics with high doses of vitamin A can increase the risk of pseudotumor cerebri.
Benign intracranial hypertension (pseudotumor cerebri) can occur with tetracyclines and with acute or chronic vitamin A toxicity. Case reports suggest that taking tetracyclines and vitamin A concurrently can increase the risk of this condition. Avoid high doses of vitamin A in people taking tetracyclines chronically.

Likelihood Possible Evidence D
Warfarin (Coumadin)

Theoretically, high doses of vitamin A could increase the risk of bleeding with warfarin.
Vitamin A toxicity is associated with hemorrhage and hypoprothrombinemia, possibly due to vitamin K antagonism. Advise patients taking warfarin to avoid doses of vitamin A above the tolerable upper intake level of 10,000 IU/day for adults.

Likelihood Possible Evidence D
Vitamin A 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

Potassium3 drug types · 62 drugs

Ace Inhibitors (Aceis)

Using ACEIs with high doses of potassium increases the risk of hyperkalemia.
ACEIs block the actions of the renin-angiotensin-aldosterone system and reduce potassium excretion. Concomitant use of these drugs with potassium supplements increases the risk of hyperkalemia. However, concomitant use of these drugs with moderate dietary potassium intake (about 3775-5200 mg daily) does not increase serum potassium levels.

Likelihood Likely Evidence C
Angiotensin Receptor Blockers (Arbs)

Using ARBs with high doses of potassium increases the risk of hyperkalemia.
ARBs block the actions of the renin-angiotensin-aldosterone system and reduce potassium excretion. Concomitant use of these drugs with potassium supplements increases the risk of hyperkalemia. However, concomitant use of these drugs with moderate dietary potassium intake (about 3775-5200 mg daily) does not increase serum potassium levels.

Likelihood Likely Evidence C
Potassium-Sparing Diuretics

Concomitant use increases the risk of hyperkalemia.
Using potassium-sparing diuretics with potassium supplements increases the risk of hyperkalemia.

Likelihood Likely Evidence C
Potassium full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Vitamin C, from the product label.

Isotonix

See all Isotonix products
Name
Market America, Inc.
Street Address
1302 Pleasant Ridge Road
City
Greensboro
State
NC
ZipCode
27409
Pharmacist Counseling Corner

Vitamin C by Isotonix: Common Questions

Does Vitamin C by Isotonix interact with any medications?
Yes. Based on its ingredients, Vitamin C has a known interaction with 550 medications, including 9 rated major. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Vitamin C contains 3 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.
Is it safe to take this if I'm on birth control?
Vitamin C in this product can increase estrogen levels from birth control pills or hormone replacement therapy, potentially raising side effects. Talk to your doctor or pharmacist before adding it—your dose may need adjusting.
Can I take this with my blood pressure medication?
It depends on which one you take. Potassium in this product can dangerously raise your blood potassium levels if you're on ACE inhibitors, ARBs, or potassium-sparing diuretics. Mention this product to your pharmacist so they can check your specific medication.
What happens if I take too much of this powder?
High doses of vitamin A can cause liver damage, headaches, and skin problems; very high doses are serious. High-dose vitamin C can cause kidney stones, stomach cramps, and diarrhea. Stick to the recommended dose on the label.
Is this safe during pregnancy?
Normal dietary amounts of vitamin A and C are fine during pregnancy, but high-dose supplements of both should be avoided because high vitamin A can cause birth defects. Potassium from food is appropriate; talk to your doctor before using a potassium supplement.
What is potassium in this supplement for?
Potassium is an essential mineral that helps your heart beat regularly, maintains muscle function, and regulates blood pressure. This product includes it as an active ingredient.
Will this interfere with my thyroid medication?
Vitamin C in this product can increase how much thyroid medication your body absorbs, which may change your blood levels and require your doctor to adjust your dose. Let your pharmacist know you're taking this.

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.

Vitamin C label
Go deeper

The Full Monographs Behind Vitamin C’s Ingredients

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

Herb & supplement monograph

Vitamin A

Interacts with 387 drugs

Vitamin A is an essential nutrient important for vision, skin, immune function, and growth. Most people get enough from a balanced diet, and supplements are mainly useful for correcting a tr...

Read the full Vitamin A 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

Potassium

Interacts with 62 drugs

Potassium is an essential mineral your body needs for nerve signals, muscle function, and a steady heartbeat, and most people get enough from a balanced diet rich in fruits and vegetables. P...

Read the full Potassium monograph →
Sources

Sources & How We Checked

Vitamin C'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 94 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.

Vitamin A 31 references
  1. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  2. Griffiths JK. The vitamin A paradox. J Pediatr 2000;137:604-7.. PubMed
  3. Hardman JG, Limbird LL, Molinoff PB, eds. Goodman and Gillman's The Pharmacological Basis of Therapeutics, 9th ed. New York, NY: McGraw-Hill, 1996.
  4. Hansten PD, Horn JR. Drug Interactions Analysis and Management. Vancouver, WA: Applied Therapeutics Inc., 1997 and updates.
  5. FDA Talk Paper. Vitamin A and birth defects (T95-56). Food and Drug Administration, U.S. Department of Health and Human Services, Rockville, MD. October 6, 1995.
  6. Russell RM. The vitamin A spectrum: from deficiency to toxicity. Am J Clin Nutr 2000;71:878-84. PubMed
  7. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2002.
  8. Feskanich D, Singh V, Willett WC, Colditz GA. Vitamin A intake and hip fractures among postmenopausal women. JAMA 2002;287:47-54. PubMed
  9. Melhus H, Michaelsson K, Kindmark A, et al. Excessive dietary intake of vitamin A is associated with reduced bone mineral density and increased risk for hip fracture. Ann Intern Med 1998;129:770-8. PubMed
  10. Michaelsson K, Lithell H, Vessby B, Melhus H. Serum retinol levels and the risk of fracture. N Engl J Med 2003;348:287-94.. PubMed
  11. Botterweck AA, van den Brandt PA, Goldbohm RA. Vitamins, carotenoids, dietary fiber, and the risk of gastric carcinoma: results from a prospective study after 6.3 years of follow-up. Cancer 2000;88:737-48.. DOI
  12. Meyskens FL Jr, Graham V, Chvapil M, et al. A phase I trial of beta-all-trans-retinoic acid delivered via a collagen sponge and a cervical cap for mild or moderate intraepithelial cervical neoplasia. J Natl Cancer Inst 1983;71:921-5..
  13. Hathcock JN, Hattan DG, Jenkins MY, et al. Evaluation of vitamin A toxicity. Am J Clin Nutr 1990;52:183-202.. PubMed
  14. Walters BN, Gubbay SS. Tetracycline and benign intracranial hypertension: report of five cases. Br Med J 1981;282:19-20.. PubMed
  15. Pearson MG, Littlewood SM, Bowden AN. Tetracycline and benign intracranial hypertension (letter). Br Med J 1981;282:568-9.. PubMed
  16. Azais-Braesco V, Pascal G. Vitamin A in pregnancy: requirements and safety limits. Am J Clin Nutr 2000;71:1325S-33S. PubMed
  17. Smedts HP, de Vries JH, Rakhshandehroo M, et al. High maternal vitamin E intake by diet or supplements is associated with congenital heart defects in the offspring. BJOG 2009;116:416-23. PubMed
  18. Grotto, I., Mimouni, M., Gdalevich, M., and Mimouni, D. Vitamin A supplementation and childhood morbidity from diarrhea and respiratory infections: a meta-analysis. J Pediatr 2003;142(3):297-304. PubMed
  19. Mahalanabis, D., Lahiri, M., Paul, D., Gupta, S., Gupta, A., Wahed, M. A., and Khaled, M. A. Randomized, double-blind, placebo-controlled clinical trial of the efficacy of treatment with zinc or vitamin A in infants and young children with severe acute l
  20. Long, K. Z., Montoya, Y., Hertzmark, E., Santos, J. I., and Rosado, J. L. A double-blind, randomized, clinical trial of the effect of vitamin A and zinc supplementation on diarrheal disease and respiratory tract infections in children in Mexico City, Mex
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Vitamin C 51 references
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Potassium 12 references
  1. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  2. Gennaro A. Remington: The Science and Practice of Pharmacy. 19th ed. Lippincott: Williams & Wilkins, 1996.
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  4. Phillips, C. O., Kashani, A., Ko, D. K., Francis, G., and Krumholz, H. M. Adverse effects of combination angiotensin II receptor blockers plus angiotensin-converting enzyme inhibitors for left ventricular dysfunction: a quantitative review of data from ra DOI
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  6. Raf, L. E. Enteric-coated potassium chloride tablets and ulcer of the small intestine. Acta Chir Scand Suppl 1967;(374):1-87.
  7. Potassium chloride oral solution [package insert]. Allentown, PA: Lehigh Valley Technologies, Inc.; 2014.
  8. Potassium chloride injection [package insert]. Lake Forest, IL: Hospira Inc.; 2009.
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See these in context on the Potassium monograph →

Parts of this content are provided by the Therapeutic Research Center, LLC.

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.

© 2021 Therapeutic Research Center, LLC

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