What is the recommended dose of Vitamin C?

- **RDA (adult women):** 75mg; **Men:** 90mg - **EU recommendation:** Women 95mg, Men 110mg - **For immune support (athletes):** Up to 2,000mg/day - **For cold duration reduction:** 200-2,000mg/day...

Is Vitamin C safe to take daily?

Vitamin C is rated "Prescription Interactions" based on clinical evidence. - **Common at >3g/day:** Diarrhea (most common), nausea, abdominal pain, rash - **At normal doses:** Well tolerated

Does Vitamin C interact with any medications?

Vitamin C has 7 known drug interactions, including interactions with Deferoxamine, Amphetamines (Adderall, etc.), Warfarin. Check with your doctor before combining with prescription medications.

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Ingredient Research

Graded against 173,636 supplements + 177 published clinical interactions, sourced from PubMed, FDA CAERS, openFDA, NIH DSLD

Vitamin C

STRONG EVIDENCEVitaminLast updated April 5, 2026

AVELOR SUMMARY

Vitamin C is the world's most popular supplement — and the most overhyped. Our research, from 102 RCTs, 15 meta-analyses, and 67,662 participants, reveals the truth: it does NOT prevent colds (Grade D), provides only a small reduction in cold duration (Grade C), and most of its other benefits require you to actually be deficient. That said, it's a potent antioxidant, supports immune function, and enhances iron absorption. It's essential — just not the miracle cure people think it is.

EVIDENCE GRADES

Plasma Vitamin C increaseStrong — obvious

Blood PressureStrong

Blood GlucoseModerate — small improvement

InsulinModerate — small decrease

Oxidative StressModerate

Cold PreventionNo effect — 40 studies, 21,620 participants

Cold SymptomsNo effect — 5 studies

Cold DurationSmall improvement — worth ~8% shorter colds

OPTIMAL DOSAGE

RDA (adult women): 75mg; Men: 90mg
EU recommendation: Women 95mg, Men 110mg
For immune support (athletes): Up to 2,000mg/day
For cold duration reduction: 200-2,000mg/day
UL: 2,000mg/day from supplements
Best forms: Ascorbic acid (cheapest, most studied), sodium ascorbate (buffered, easier on stomach)
Timing: Can be taken any time. Split doses if >1,000mg to reduce GI effects.
Key insight: Easily obtained through diet. 1 orange = ~70mg. Supplementation unnecessary for most people eating fruits/vegetables.

Scan a supplement containing Vitamin C

DRUG INTERACTIONS

DeferoxamineSevere

Enhances drug effects

Limit to 200mg/day with deferoxamine. Avoid in heart failure patients.

Amphetamines (Adderall, etc.)Moderate

Reduces drug absorption

Don't take vitamin C with ADHD stimulant medications.

WarfarinModerate

May reduce effectiveness

Monitor INR if taking >1g/day vitamin C.

LevothyroxineModerate

Increases drug absorption

Monitor thyroid levels.

IronMinor

Enhances iron absorption

Useful pairing for iron-deficient people. Avoid if hemochromatosis.

AcetaminophenMinor

Increases drug half-life

Not clinically significant at normal doses.

Chemotherapy drugs (doxorubicin, cisplatin, vincristine, methotrexate, imatinib)Unknown

May reduce drug effectiveness

Discuss with oncologist before supplementing during chemo.

SAFETY PROFILE

Side Effects

Common at >3g/day: Diarrhea (most common), nausea, abdominal pain, rash
At normal doses: Well tolerated

Drug Interactions

Precautions

Pregnancy: Safe. RDA 80-85mg/day.
Breastfeeding: Safe. RDA 115-120mg/day.
Kidney disease: Caution. High-dose (>2g) can cause oxalate nephropathy and acute renal failure.
Kidney stones: Supplementation may increase risk, particularly in men.
G6PD deficiency: Can cause acute hemolysis. Caution with supplementation.
Hemochromatosis: Not recommended — increases iron absorption and overload risk.
Continuous glucose monitor users: Can interfere with CGM readings (falsely high). Limit to 500mg/day.
Dental erosion: Chewable vitamin C tablets may cause dental erosion with long-term use.

Quality Concerns

Oral contraceptives may lower vitamin C levels, but evidence is mixed and outdated.

WADA Status

Not Prohibited.

WHO SHOULD BE CAREFUL

QUALITY CONCERNS

Oral contraceptives may lower vitamin C levels, but evidence is mixed and outdated.

HOW AVELOR SCORES THIS

Present at 60-500mg:✅ Green flag — reasonable supplemental dose

Present at >2,000mg:⚠️ Yellow flag — exceeds UL, kidney stone risk increases

Marketed as "cold cure":⚠️ Yellow flag — misleading; evidence does NOT support cold prevention

In a product for ADHD/focus that also contains vitamin C:⚠️ Yellow flag — may reduce effectiveness of stimulant ADHD medications

RELATED RESEARCH

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Scan Your Vitamin C Supplement Browse all ingredients

Independently graded against 173,636 indexed supplements with 177 published clinical interactions, sourced from PubMed, FDA CAERS, openFDA, and NIH DSLD | Last updated: April 5, 2026

Not medical advice. Based on published clinical research and systematic reviews.

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Browse All 834 Ingredients Browse All 20 Conditions

Ingredient Research

Graded against 173,636 supplements + 177 published clinical interactions, sourced from PubMed, FDA CAERS, openFDA, NIH DSLD

Vitamin C

STRONG EVIDENCEVitaminLast updated April 5, 2026

AVELOR SUMMARY

EVIDENCE GRADES

Plasma Vitamin C increaseStrong — obvious

Blood PressureStrong

Blood GlucoseModerate — small improvement

InsulinModerate — small decrease

Oxidative StressModerate

Cold PreventionNo effect — 40 studies, 21,620 participants

Cold SymptomsNo effect — 5 studies

Cold DurationSmall improvement — worth ~8% shorter colds

OPTIMAL DOSAGE

RDA (adult women): 75mg; Men: 90mg
EU recommendation: Women 95mg, Men 110mg
For immune support (athletes): Up to 2,000mg/day
For cold duration reduction: 200-2,000mg/day
UL: 2,000mg/day from supplements
Best forms: Ascorbic acid (cheapest, most studied), sodium ascorbate (buffered, easier on stomach)
Timing: Can be taken any time. Split doses if >1,000mg to reduce GI effects.
Key insight: Easily obtained through diet. 1 orange = ~70mg. Supplementation unnecessary for most people eating fruits/vegetables.

Scan a supplement containing Vitamin C

DRUG INTERACTIONS

DeferoxamineSevere

Enhances drug effects

Limit to 200mg/day with deferoxamine. Avoid in heart failure patients.

Amphetamines (Adderall, etc.)Moderate

Reduces drug absorption

Don't take vitamin C with ADHD stimulant medications.

WarfarinModerate

May reduce effectiveness

Monitor INR if taking >1g/day vitamin C.

LevothyroxineModerate

Increases drug absorption

Monitor thyroid levels.

IronMinor

Enhances iron absorption

Useful pairing for iron-deficient people. Avoid if hemochromatosis.

AcetaminophenMinor

Increases drug half-life

Not clinically significant at normal doses.

Chemotherapy drugs (doxorubicin, cisplatin, vincristine, methotrexate, imatinib)Unknown

May reduce drug effectiveness

Discuss with oncologist before supplementing during chemo.

SAFETY PROFILE

Side Effects

Common at >3g/day: Diarrhea (most common), nausea, abdominal pain, rash
At normal doses: Well tolerated

Drug Interactions

Precautions

Pregnancy: Safe. RDA 80-85mg/day.
Breastfeeding: Safe. RDA 115-120mg/day.
Kidney disease: Caution. High-dose (>2g) can cause oxalate nephropathy and acute renal failure.
Kidney stones: Supplementation may increase risk, particularly in men.
G6PD deficiency: Can cause acute hemolysis. Caution with supplementation.
Hemochromatosis: Not recommended — increases iron absorption and overload risk.
Continuous glucose monitor users: Can interfere with CGM readings (falsely high). Limit to 500mg/day.
Dental erosion: Chewable vitamin C tablets may cause dental erosion with long-term use.

Quality Concerns

Oral contraceptives may lower vitamin C levels, but evidence is mixed and outdated.

WADA Status

Not Prohibited.

WHO SHOULD BE CAREFUL

QUALITY CONCERNS

Oral contraceptives may lower vitamin C levels, but evidence is mixed and outdated.

HOW AVELOR SCORES THIS

Present at 60-500mg:✅ Green flag — reasonable supplemental dose

Present at >2,000mg:⚠️ Yellow flag — exceeds UL, kidney stone risk increases

Marketed as "cold cure":⚠️ Yellow flag — misleading; evidence does NOT support cold prevention

In a product for ADHD/focus that also contains vitamin C:⚠️ Yellow flag — may reduce effectiveness of stimulant ADHD medications

RELATED RESEARCH

Acerola Cherry

Amla

BiotinBiotin is a cofactor for five carboxylase enzymes critical to metabolism: pyruva

Amla

Scan Your Vitamin C Supplement Browse all ingredients

Independently graded against 173,636 indexed supplements with 177 published clinical interactions, sourced from PubMed, FDA CAERS, openFDA, and NIH DSLD | Last updated: April 5, 2026

Not medical advice. Based on published clinical research and systematic reviews.

Discover More

Helps With

Immune Support Hair Loss Inflammation

Related Ingredients

Zinc Vitamin D Iron

Explore

Browse All 834 Ingredients Browse All 20 Conditions