Vitamin C Supplements: Benefits, Dosage and Safety
Vitamin C supplements are rarely needed if you eat fruit and vegetables: adults need just 75–90 mg a day. Regular use may slightly shorten colds but doesn't prevent them for most people. Doses above 2,000 mg a day often cause stomach upset.
Evidence at a glance
| Use | Grade | What the research shows |
|---|---|---|
| Shorter colds (regular use) | B | Slight reduction in cold duration. |
| Preventing colds | D | No effect for most people. |
| Iron absorption | A | Increases absorption of plant-based iron. |
A: strong, consistent human evidence · B: moderate · C: limited or mixed · D: good evidence of no benefit.
Vitamin C is needed to make collagen, absorb iron and protect cells from damage.
How to take it
Food first: a single orange or half a red pepper covers most of the RDA. If you supplement, 100–500 mg is plenty. Details are in how much vitamin C per day.
Safety and interactions
High doses can cause diarrhea and may raise kidney stone risk in some people. People with hemochromatosis should avoid high doses.
Always tell your doctor and pharmacist about the supplements you take. Check combinations with our interaction checker.
Sources
This page is for education and is not a substitute for advice from your doctor. Read our medical disclaimer.