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Comment by pydry | Hacker News Reader

I've gotten wildly different estimates about how much to take - including some that overlap with how much is supposed to be harmful.

Some people say 500 IU is enough, some say you need 4000 IU per day.

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There's no way to know without testing. The optimal supplement amount for you could be zero, or it could be even more than 4000 IU per day. This depends on genetics, diet, ultraviolet light exposure, body composition, and a variety of other factors. So, the only way to be sure is to get periodic blood tests and titrate the supplements up or down to hit the target level.

If you don't want to hassle with testing then something like 600 IU will be adequate (although not necessarily optimal) for most adults. YMMV.

https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessiona...

This says 30,000 to 50,000 IU is fine: https://vers.substack.com/p/doctors-are-idiots-vitamin-d-meg...

According to the National Academy of Medicine, formerly known as the Institute of Medicine, 4,000 IU is the safe upper level of daily vitamin D intake. However, doses up to 10,000 IU have not been shown to cause toxicity in healthy individuals (11Trusted Source, 16Trusted Source).

Vitamin D toxicity is generally caused by excessive doses of vitamin D supplements, not by diet or sun exposure (17Trusted Source, 18Trusted Source).

Although vitamin D toxicity is a very rare condition, recent increases in supplement use may lead to an increase in reported cases.

A daily intake ranging from 40,000–100,000 IU (1,000–2,500 mcg), for 1 to several months, has been shown to cause toxicity in humans (15Trusted Source, 19Trusted Source, 20Trusted Source, 21Trusted Source, 22Trusted Source).

https://www.healthline.com/nutrition/how-much-vitamin-d-is-t...

Thanks for the additional info!

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