Interactions on record — worth a quick check against your medications. Based on 2 of 4 ingredients. Check your meds →
Dietary supplement

Collagen-9 Unflavored Ingredients & Drug Interactions

by Shaklee

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

First and foremost: checking Collagen-9 Unflavored 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

Collagen-9 Unflavored is a dietary supplement by Shaklee with 4 active ingredients. Its ingredients are commonly taken for hair growth and thinning hair, brittle nails, skin health.Based on those ingredients, 207 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Vitamin C. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

Jump to a section

Check Your Meds Against Collagen-9 Unflavored by Shaklee

Ask about any prescription or over-the-counter medication and we check it for interactions with Collagen-9 Unflavored by Shaklee — and tell you which ingredient is responsible.

Pharmacist-reviewed data Checks every ingredient Answer in seconds
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HelloPharmacist Scorecard of Collagen-9 Unflavored by Shaklee

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 16, 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.

Collagen-9 Unflavored contains three active ingredients: biotin, vitamin C, and collagen. Biotin is a B vitamin that supports hair, skin, and nail health; vitamin C is an antioxidant that plays a role in immune function and tissue repair.

Collagen is a structural protein that may help with skin, joint, and connective-tissue health. The powder also contains pea protein as an inactive ingredient.

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: daily beauty and connective tissue support.
  • We looked for evidence on: Aging skin, Brittle nails, wound healing, joint health.
  • The closest evidence on file: Biotin is rated "Insufficient Reliable Evidence To Rate" for Brittle nails (Natural Medicines).
  • Also on file: Vitamin C is rated "Insufficient Reliable Evidence To Rate" for Aging skin, Wound healing.

Biotin is likely effective for biotin deficiency. For other uses — multiple sclerosis, seborrheic dermatitis, and hair loss (alopecia areata) — the evidence is either insufficient to rate or suggests it's not effective.

Vitamin C is effective for vitamin C deficiency and possibly effective for anemia of chronic disease, atrial fibrillation, cataracts, and exercise-related respiratory infections. We don't have effectiveness data on file for collagen.

The evidence, ingredient by ingredient Biotin Vitamin C

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 2 of the 2 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 2 of 2.
  • General safety write-ups exist for 2 of 2.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Biotin is generally well tolerated, even at fairly high doses, because your body excretes excess in urine. The main caution is high-dose biotin — normal dietary and supplement amounts are fine, but talk with your doctor before taking large-dose products.

Vitamin C is also generally safe at normal dietary and supplement doses. At very high doses (above 2 grams daily), it can cause abdominal cramps, heartburn, diarrhea, nausea, or kidney stones in people prone to them.

Biotin in pregnancy and lactation is rated likely safe; for vitamin C, normal amounts are likely safe, but high-dose supplements should be avoided in pregnancy unless your doctor advises otherwise.

Side effects, ingredient by ingredient Biotin Vitamin C

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?
  • 1 of the 2 matched ingredients can interact with medications — Vitamin C.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; cancer treatments.
  • For scale: 207 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.

If you take blood thinners (warfarin), birth control or hormone replacement therapy, thyroid medication (levothyroxine), or chemotherapy drugs, double-check this product with your doctor or pharmacist first — vitamin C can affect how these work. The same goes for indinavir and fluphenazine, and for any aluminum-containing compounds you may take.

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 powder might appeal to you if you're looking to support hair, skin, nail, or joint health with biotin and collagen. If you take blood thinners, birth control, thyroid medication, or chemotherapy, check your exact medications with your doctor or pharmacist before starting — vitamin C in this product can interact with them.

Talk it over with your healthcare provider to see if it's a fit for you.

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

Assessment coverage: 2 of 3 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Nov 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 Collagen-9 Unflavored, straight from the product label.

Brand Shaklee
Net contents 16.4 Ounce(s); 464 Gram(s)
Market status On market
Date entered into DSLD Nov 22, 2023
DSLD ID 301157
Product type Other Combinations
Supplement form Powder
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), Organic, 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 Collagen-9 Unflavored by Shaklee, 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:
11.6 Gram(s)
Maximum serving Sizes:
11.6 Gram(s)
Servings per container
40
IngredientAmount% DV
Protein10 Gram(s)--
Biotin30 mcg100%
Vitamin C90 mg100%
Calories45 Calorie(s)--
Collagen10 Gram(s)--

Other ingredients: Pea 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

Your daily beauty booster

Dr Shaklee

Formula

Introducing the most complete collagen protein product. Uniquely designed to include all 9 essential amino acids needed to support protein synthesis, including collagen, which aids in the formation of all our connective tissue (skin, bones, muscles, tendons, ligaments). Each serving delivers 10g of hydrolyzed collagen from types I and III, derived from a grass-fed, pasture-raised bovine source.

The most complete collagen product Includes all 9 essential amino acids that are required by the body to support protein synthesis, including collagen. 100% DV of Biotin Supports healthy hair, skin, and nails. 100% DV of vitamin C Protects our bodies against damage caused by free radicals and aids in collagen synthesis. 100% hydrolyzed collagen For quicker digestion and absorption.

Uniquely designed to contain all 9 essential amino acids to support protein synthesis

10 g collagen per serving

Suggested/Recommended/Usage/Directions

Add it to your favorite drink (we love it mixed in a coffee or shake)!

Dissolves easily into your favorite drink.

Directions: Add two scoops to your favorite drink (like shakes, smoothies, matcha, or coffee). For best results, add gradually while stirring.

Seals/Symbols

Safe Proven Shaklee Since 1956 100% Guaranteed

Formulation

Non GMO

Grass fed

GF gluten free Dairy free

Beyond organic

100% carbon neutral

No artificial flavors, sweeteners, colors, or preservatives

Hair, skin, nail & joint support

FDA Statement of Identity

Dietary Supplement Powder

Precautions

Manufactured in a facility that may also process tree nuts, milk, egg, soy, wheat, shellfish, and fish.

Caution: If pregnant or nursing, consult your physician prior to use.

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.

Storage

Store at room temperature. Protect from moisture.

Brand IP Statement(s)

Safe Proven Shaklee Since 1956 100% Guaranteed

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

See for yourself

Collagen-9 Unflavored by Shaklee label

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

Collagen-9 Unflavored 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 Collagen-9 Unflavored by Shaklee

These are the 4 active ingredients this product is made of. Select any to open its full monograph.

Serving size11.6 Gram(s) Dosage formPowder Servings per container40 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.

Protein

10 Gram(s) per serving

Biotin

No known
interactions
30 mcg per serving

Biotin (vitamin B7) is a water-soluble vitamin your body needs to turn food into energy and to support healthy hair, skin, and nails. Most people get...

Biotin monograph & interactions

Vitamin C

Interacts with
207 drugs
90 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

Collagen

10 Gram(s) per serving Form: Collagen Type I, Hydrolyzed, Collagen Type III, Hydrolyzed

Other (inactive) ingredients: Pea Protein. These complete the product’s ingredient list but are not active constituents.

Interaction report

Collagen-9 Unflavored by Shaklee Drug Interactions

Want to check YOUR meds against Collagen-9 Unflavored?

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
207Drugs
101 Moderate 106 Minor

Ingredients driving the most interactions

Vitamin C 207

Individual Drug Interactions

The ingredients in Collagen-9 Unflavored interact with 207 drugs. Click any drug to see the details.

1 of the 4 ingredients in Collagen-9 Unflavored interact with drugs. Each result below shows which ingredient is responsible. Vitamin C

Each ingredient & the kinds of drugs it affects

For each ingredient in Collagen-9 Unflavored with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

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
The maker

Brand information

Manufacturer and brand details for Collagen-9 Unflavored, from the product label.

Shaklee

See all Shaklee products
Name
Shaklee Corporation
Street Address
4747 Willow Road
City
Pleasanton
State
CA
ZipCode
94588
Phone Number
925.734.3638
Pharmacist Counseling Corner

Collagen-9 Unflavored by Shaklee: Common Questions

Does Collagen-9 Unflavored by Shaklee interact with any medications?
Yes. Based on its ingredients, Collagen-9 Unflavored has a known interaction with 207 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Collagen-9 Unflavored contains 4 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 this safe to take while pregnant or breastfeeding?
Biotin is rated likely safe in pregnancy and lactation. Vitamin C at normal amounts is likely safe; high-dose supplements should be avoided in pregnancy unless your doctor advises it. We don't have pregnancy or breastfeeding data for collagen. Talk with your doctor or pharmacist about whether this product is right for you during pregnancy or while breastfeeding.
Can high-dose vitamin C in this powder cause side effects?
Vitamin C is well tolerated at normal supplement doses. At high doses above 2 grams daily, it can cause abdominal cramps, heartburn, diarrhea, nausea, or kidney stones in people who are prone to them. This product's dose of vitamin C would need to be very high to trigger those effects, but check the label to see how much you're getting per serving.
What is biotin used for?
Biotin is a B vitamin that supports the health of hair, skin, and nails. It's likely effective for treating biotin deficiency. For other uses like hair loss or skin conditions, the evidence is either limited or suggests it may not be effective.
Does this powder have any fillers?
The product contains pea protein as an inactive ingredient in addition to the three active ingredients.
Will this help my thyroid medication work better?
Vitamin C can actually increase how much levothyroxine (thyroid medication) your body absorbs, which may raise your thyroid hormone levels. If you take thyroid medication, check with your doctor or pharmacist before adding this product — they may need to adjust your dose.

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.

Collagen-9 Unflavored label
Go deeper

The Full Monographs Behind Collagen-9 Unflavored’s Ingredients

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

Herb & supplement monograph

Biotin

Biotin (vitamin B7) is a water-soluble vitamin your body needs to turn food into energy and to support healthy hair, skin, and nails. Most people get plenty from a normal diet, and true defi...

Read the full Biotin 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 →
Sources

Sources & How We Checked

Collagen-9 Unflavored'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 55 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.

Biotin 4 references
  1. Debourdeau PM, Djezzar S, Estival JL, et al. Life-threatening eosinophilic pleuropericardial effusion related to vitamins B5 and H. Ann Pharmacother 2001;35:424-6. DOI
  2. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (2000). Washington, DC: National Academy Press, 2000. Available at: http://b
  3. Mock DM, Quirk JG, Mock NI. Marginal biotin deficiency during normal pregnancy. Am J Clin Nutr 2002;75:295-9. PubMed
  4. Sedel F, Papeix C, Bellanger A, Touitou V, Lebrun-Frenay C, Galanaud D, et al. High doses of biotin in chronic progressive multiple sclerosis: a pilot study.Mult Scler Relat Disord. 2015;4(2):159-69. doi: 10.1016/j.msard.2015.01.005. PubMed

See these in context on the Biotin monograph →

Vitamin C 51 references
  1. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  2. Back DJ, Breckenridge AM, MacIver M, et al. Interaction of ethinyloestradiol with ascorbic acid in man. Br Med J (Clin Res Ed) 1981;282:1516.
  3. Morris JC, Beeley L, Ballantine N. Interaction of ethinyloestradiol with ascorbic acid in man [letter]. Br Med J (Clin Res Ed) 1981;283:503.
  4. Labriola D, Livingston R. Possible interactions between dietary antioxidants and chemotherapy. Oncology 1999;13:1003-8.
  5. Dwyer JH, Merz NB, Shirocre AM, et al. Progression of early atherosclerosis and intake of vitamin C and vitamin E from supplements and food. The Los Angeles Atherosclerosis Study. 41st Annual Conference on Cardiovascular Disease Epidemiology and Prevent
  6. Levine M, Rumsey SC, Daruwala R, et al. Criteria and recommendations for vitamin C intake. JAMA 1999;281:1415-23. PubMed
  7. Hansten PD, Horn JR. Drug Interactions Analysis and Management. Vancouver, WA: Applied Therapeutics Inc., 1997 and updates.
  8. Segal S, Kaminski S. Drug-nutrient interactions. American Druggist 1996 Jul;42-8.
  9. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Press, 2000. Available at: http://www.nap.edu/books/0309069351/html/.
  10. Houston JB, Levy G. Drug biotransformation interactions in man VI: Acetaminophen and ascorbic acid. J Pharm Sci 1976;65:1218-21. PubMed
  11. Brown BG, Zhao XQ, Chait A, et al. Simvastatin and niacin, antioxidant vitamins, or the combination for the prevention of coronary disease. N Engl J Med 2001;345:1583-93. DOI
  12. Rosenthal G. Interaction of ascorbic acid and warfarin. JAMA 1971;215:1671. DOI
  13. Hume R, Johnstone JM, Weyers E. Interaction of ascorbic acid and warfarin. JAMA 1972;219:1479. DOI
  14. Smith EC, Skalski RJ, Johnson GC, Rossi GV. Interaction of ascorbic acid and warfarin. JAMA 1972;221:1166. DOI
  15. Traxer O, Huet B, Poindexter J, et al. Effect of ascorbic acid consumption on urinary stone risk factors. J Urol 2003;170:397-401.. PubMed
  16. Domingo JL, Gomez M, Llobet JM, Richart C. Effect of ascorbic acid on gastrointestinal aluminum absorption (letter). Lancet 1991;338:1467.
  17. Domingo JL, Gomez M, Llobet JM, Corbella J. Influence of some dietary constituents on aluminum absorption and retention in rats. Kidney Int 1991;39:598-601. PubMed
  18. Partridge NA, Regnier FE, White JL, Hem SL. Influence of dietary constituents on intestinal absorption of aluminum. Kidney Int 1989;35:1413-7. PubMed
  19. Mc Leod DC, Nahata MC. Inefficacy of ascorbic acid as a urinary acidifier (letter). N Engl J Med 1977;296:1413. DOI
  20. Hansten PD, Hayton WL. Effect of antacid and ascorbic acid on serum salicylate concentration. J Clin Pharmacol 1980;20:326-31. PubMed
  21. Dysken MW, Cumming RJ, Channon RA, Davis JM. Drug interaction between ascorbic acid and fluphenazine. JAMA 1979;241:2008. DOI
  22. Vihtamaki T, Parantainen J, Koivisto AM, et al. Oral ascorbic acid increases plasma oestradiol during postmenopausal hormone replacement therapy. Maturitas 2002;42:129-35. PubMed
  23. Slain D, Amsden JR, Khakoo RA, et al. Effect of high-dose vitamin C on the steady-state pharmacokinetics of the protease inhibitor indinavir in healthy volunteers. Pharmacotherapy 2005;25:165-70. PubMed
  24. Cheung MC, Zhao XQ, Chait A, et al. Antioxidant supplements block the response of HDL to simvastatin-niacin therapy in patients with coronary artery disease and low HDL. Arterioscler Thromb Vasc Biol 2001;21:1320-6. PubMed
  25. Feetam CL, Leach RH, Meynell MJ. Lack of a clinically important interaction between warfarin and ascorbic acid. Toxicol Appl Pharmacol 1975;31:544-7. PubMed
  26. Weintraub M, Griner PF. Warfarin and ascorbic acid: lack of evidence for a drug interaction. Toxicol Appl Pharmacol 1974;28:53-6. PubMed
  27. Lee DH, Folsom AR, Harnack L, et al. Does supplemental vitamin C increase cardiovascular disease risk in women with diabetes? Am J Clin Nutr 2004;80:1194-200. PubMed
  28. Taylor EN, Stampfer MJ, Curhan GC. Dietary factors and the risk of incident kidney stones in men: new insights after 14 years of follow-up. J Am Soc Nephrol 2004;15:3225-32. PubMed
  29. Ward NC, Hodgson JM, Croft KD, et al. The combination of vitamin C and grape-seed polyphenols increases blood pressure: a randomized, double-blind, placebo-controlled trial. J Hypertens 2005;23:427-34.. PubMed
  30. Prasad KN. Rationale for using high-dose multiple dietary antioxidants as an adjunct to radiation therapy and chemotherapy. J Nutr 2004;134:3182S-3S. PubMed
  31. Conklin KA. Cancer chemotherapy and antioxidants. J Nutr 2004;134:3201S-3204S. PubMed
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See these in context on the Vitamin C monograph →

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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.

© 2021 Therapeutic Research Center, LLC

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