How much vitamin D do I need?

Info source: http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/vitamin-d/index.html#vitamin-d-sources-and-function

The Institute of Medicine's (IOM) recommended daily intake of vitamin D is 600 IU for people ages 1 to 70, and 800 IU after age 70. (7) Yet this is overly conservative, since the best available evidence shows optimal intakes are higher, at least 800–1,000 IU for adults.

In extremely high doses—hundreds of thousands of IU or more—vitamin D is toxic and can even cause death. But in children over the age of 9 and in adults, taking up to 4,000 IU per day as a supplement is safe; ages 4 to 8, up to 3,000 IU; ages 1 to 3, 2,500 IU; ages 6 to 12 months, up to 1,500 IU; and ages 0 to 6 months, up to 1,000 IU. (7)

Many people may need 2,000 IU per day (or more) for adequate blood levels, particularly if they have darker skin, spend winters at higher latitudes (such as the northern U.S.), or spend little time in the sun. If you fall into one of these groups, which would include most of the U.S. population, taking 2,000 IU is reasonable and well within the safe range for adults. As always, it's a good idea to discuss use of supplements with your doctor, and he or she may want to order a vitamin D blood test.

To prevent rickets, the American Academy of Pediatrics recommends vitamin D supplements of 400 IU per day for breastfed infants, and also for non-breastfed infants and children who do not drink at least a liter of vitamin D fortified milk each day. (6) Infants and children at high risk of deficiency—those who are born premature, have dark skin, or live at high latitudes—may need supplements of up to 800 IU per day, especially in the winter.