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.
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How much vitamin C is too much?
The official ceiling is 2,000 mg a day for adults - that is the NIH's tolerable upper limit from all sources, set because past it the side effects reliably arrive: diarrhea, nausea, and abdominal cramps, with kidney stones on the worry list for heavy long-term users. The NHS draws its caution line lower, at 1,000 mg a day, where stomach pain, diarrhea, and flatulence can start. The striking part is how small the actual need is: about 90 mg a day for men and 75 mg for women (NHS: 40 mg) - one orange covers it - which means a 1,000 mg tablet delivers over ten times the requirement. Vitamin C is water-soluble, so your body excretes much of the surplus, which is why megadoses mostly buy expensive urine plus a stomach ache. The persistent myth to retire: vitamin C does not prevent colds in the general population - the evidence points to slightly shorter colds at best. If your diet includes any fruit or vegetables, a supplement is optional; if you take one, staying under 500 to 1,000 mg keeps you far from the ceiling. Pymander is a free AI doctor, 24/7 by text, that can help you sanity-check your stack.