Vitamin C
- Effective dose
- 200–1000 mg
- Evidence
- 3/5· Moderate
Last updated June 1, 2026
What it is
Vitamin C (ascorbic acid) is a water-soluble vitamin and antioxidant essential for collagen synthesis, immune function, and the absorption of non-heme iron. The body cannot make or store it well, so regular dietary or supplemental intake is required.
Benefits
Vitamin C supports immune function and collagen formation, and regular (not just at-onset) supplementation may modestly reduce the duration of colds. The RDA is 75-90 mg, while common supplemental doses range from about 200-1,000 mg per day, below the 2,000 mg upper limit.
When to take it
Taken daily with or without food; splitting larger doses improves absorption and tolerance, and pairing with plant-based iron sources aids iron uptake.
Side effects
High doses (above ~2,000 mg/day) can cause diarrhea, GI upset, and may raise the risk of kidney stones in susceptible people. Because it is water-soluble, excess is largely excreted in urine.
Sources
Products containing Vitamin C
No products in our database contain this ingredient yet.