Vitamin C Dosage Chart
Vitamin C (ascorbic acid) is a water-soluble antioxidant essential for collagen synthesis, immune function, and iron absorption. Unlike fat-soluble vitamins, excess vitamin C is excreted in urine, but very high doses still cause gastrointestinal side effects.
Vitamin C Dosage by Age Group
| Age Group | Age Range | Dose Range | Notes |
|---|---|---|---|
| Children (1–8 yr) | 1–8 years | 15–25 mg | RDA range for children |
| Adolescents (9–18 yr) | 9–18 years | 45–75 mg | RDA; higher end for teens |
| Adults (men) | 18–64 years | 90–1000 mg | RDA 90 mg; common supplement range 250–1,000 mg |
| Adults (women) | 18–64 years | 75–1000 mg | RDA 75 mg; 85 mg if pregnant |
| Adults — immune/illness support | 18–64 years | 500–2000 mg | Short-term boost; bowel tolerance varies |
| Seniors (65+) | 65+ years | 75–1000 mg | RDA unchanged; gut tolerance may be lower |
When and how to take Vitamin C
Vitamin C is absorbed best in smaller, more frequent doses (500 mg or less at a time). Taking with meals reduces stomach irritation. Split large doses throughout the day.
Available Forms
Standard form. Cheap and effective. May cause GI upset at high doses.
Most studied; pH 2.5 — acidic
Buffered, gentler on stomach. Useful for sensitive GI tract.
Lower elemental vitamin C per gram than pure ascorbic acid
Encapsulated in liposomes for enhanced cellular absorption. Popular for high-dose protocols.
May achieve higher intracellular levels than standard forms
Safety Cautions
- Upper tolerable intake level: 2,000 mg/day for adults. Exceeding causes diarrhea and GI distress.
- High doses may increase kidney stone risk in people with oxalate sensitivity.
- Smokers need 35 mg/day more than non-smokers (oxidative stress).
- Very high IV doses are used therapeutically (cancer adjunct, sepsis) — not equivalent to oral supplementation.
- May interfere with certain lab tests (blood glucose, stool guaiac) at high doses.
Frequently Asked Questions
How much vitamin C per day for adults?
The RDA for vitamin C is 90 mg/day for adult men and 75 mg/day for adult women. For immune support, many people take 500–1,000 mg/day. The upper tolerable limit is 2,000 mg/day — above this, GI side effects (diarrhea) are common.
What is the maximum vitamin C dose per day?
The Institute of Medicine sets the tolerable upper intake level (UL) at 2,000 mg/day for adults. This does not mean 2,000 mg is optimal — most benefits plateau well below 1,000 mg/day. The UL is the level above which adverse effects (kidney stones, GI distress) become more likely.
Does liposomal vitamin C absorb better?
Liposomal vitamin C may achieve higher plasma and intracellular concentrations than equivalent oral doses of ascorbic acid, especially at doses above 1,000 mg. For standard supplementation (200–500 mg), the difference is minimal. Liposomal forms are primarily useful for high-dose therapeutic protocols.
Sources & References
- NIH ODS — Vitamin C Fact Sheet
- Carr AC & Maggini S, Nutrients 2017 — Vitamin C and Immune Function
- Levine M et al., PNAS 1996 — Vitamin C pharmacokinetics