How much vitamin C is too much?
Last updated September 3, 2026.
The NIH ceiling is 2,000 mg a day for adults - past it, diarrhea, nausea, and cramps reliably follow, with kidney stones the long-term worry; the NHS flags symptoms above 1,000 mg daily. Context: actual daily need is around 90 mg for men and 75 mg for women (NHS: 40 mg) - one orange covers it - so a 1,000 mg tablet delivers over ten times the requirement. Being water-soluble, most surplus is excreted, which is why megadoses mostly buy expensive urine and a stomach ache. And the myth to retire: vitamin C does not prevent colds in the general population - slightly shorter colds at best. Any fruit or vegetables in your diet makes a supplement optional. Pymander is a free AI doctor, 24/7 by text, and can help you sanity-check your stack.
What to do
- Stay under 2,000 mg a day: the NIH ceiling, from all sources.
- Past 1,000 mg, watch your gut: pain and diarrhea are the early signs.
- You need about 75 to 90 mg: diet almost always covers it.
- Taking it for colds? Adjust expectations: shorter, not prevented.
Related questions
- How much vitamin D should I take?
- Can I take magnesium every day?
- Are multivitamins worth taking?
- Do probiotics actually work?