600 IU (15 mcg) daily for adults to age 70 and 800 IU (20 mcg) after that, per the NIH, with a hard upper limit of 4,000 IU (100 mcg); the NHS advises 10 mcg (400 IU) daily for everyone over one year old, with extra emphasis on supplementing through autumn and winter.
Many adults in northern latitudes run low, and only a blood test shows your actual level - worth having before taking big doses, because vitamin D overdose causes real harm (calcium buildup, kidney strain), unlike most vitamins. A sensible default for most adults is 400 to 1,000 IU daily, escalating only on test results. Pymander is a free AI doctor, 24/7 by text, and can help you interpret your level.
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Common questions
How much vitamin D should I take?
The mainstream targets are close but not identical. The NIH sets adult needs at 600 IU (15 micrograms) daily up to age 70, then 800 IU (20 mcg) beyond that, from all sources - food, sun, and supplements combined - and puts the safe upper limit at 4,000 IU (100 mcg) a day. The NHS is more conservative and more seasonal: 10 micrograms (400 IU) daily for adults and children over one year, with an explicit push to supplement through autumn and winter when sunlight cannot deliver. The real-world wrinkle: a large share of adults in northern latitudes run low, and the only way to know your level is a blood test - which is worth having before self-prescribing big doses, because too much vitamin D is a genuine harm (calcium buildup, kidney strain), unlike most vitamins. The sensible default for most adults: a 400 to 1,000 IU daily supplement, more only if a test says so. Pymander is a free AI doctor, 24/7 by text, that can help you interpret your level.