Vitamin C: what it does and how much you need
Vitamin C is an antioxidant. It helps the body make collagen for wound healing, helps absorb iron from plant foods, and supports the immune system. Adults need 90 milligrams for men and 75 milligrams for women, plus 35 milligrams for people who smoke, and the upper limit is 2,000 milligrams a day.
General information, not medical advice. Check with a doctor or pharmacist before taking a supplement, especially if you are pregnant or breastfeeding, take any medicine, or are under 18.
In the UK
In the UK, adults need 40 milligrams a day, and the NHS says up to 1,000 milligrams a day from supplements is unlikely to cause harm.
How much you need and the upper limit
| US (NIH) | UK (NHS) | |
|---|---|---|
| Adults need | 90 milligrams for men and 75 milligrams for women, plus 35 milligrams for people who smoke | 40 milligrams a day |
| Upper limit | 2,000 milligrams a day | Up to 1,000 milligrams a day from supplements |
The UK figure is the amount the NHS says is unlikely to cause harm. Figures are for adults.
Cautions
- Above the upper limit, vitamin C often causes diarrhoea and stomach upset.
Food sources
- Citrus fruit
- Peppers
- Kiwi
- Broccoli
- Strawberries
- Tomatoes
- Potatoes
Dose questions
Quick answers
- What does vitamin C do?
- Vitamin C is an antioxidant. It helps the body make collagen for wound healing, helps absorb iron from plant foods, and supports the immune system.
- How much vitamin C do adults need?
- Adults need 90 milligrams for men and 75 milligrams for women, plus 35 milligrams for people who smoke (US, NIH). In the UK: 40 milligrams a day (NHS).
- What is the upper limit for vitamin C?
- US: 2,000 milligrams a day. UK (NHS): up to 1,000 milligrams a day from supplements is unlikely to cause harm.
- Which foods have vitamin C?
- Citrus fruit, peppers, kiwi, broccoli, strawberries, tomatoes, potatoes.
- What should I watch out for with vitamin C?
- Above the upper limit, vitamin C often causes diarrhoea and stomach upset.
Sources
- NIH Office of Dietary Supplements fact sheet
https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/ - NHS vitamins and minerals guidance
https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-c/
Ask Supplement Check yourself
Type a vitamin, mineral or supplement, a dose, or a product name, and get the daily need, the upper limit and any cautions. Open Supplement Check, free, no sign-up.
In Claude or any app that takes MCP connectors, add https://goodturn-mcp.pages.dev/supplementcheck/mcp and ask: “Is 1000 mg of vitamin C too much?”