Is constipation a side effect of Vitamin D3?

Constipation is a possible side effect of taking too much vitamin D3 (the form of D that the body produces from sunlight). According to the National Institutes of Health's Office of Dietary Supplements, the maximum daily amount of vitamin D3 that people should consume is:
  • 1,000 to 1,500 IU for infants
  • 2,500 IU for children 1 to 3 years
  • 3,000 IU for children 4 to 8 years
  • 4,000 IU for children 9 years and older, adults and pregnant and lactating teens and women
Note that it's not possible to get too much vitamin D through sun exposure, since the body regulates its production of vitamin D. It's also very unlikely to get too much vitamin D from foods. So limiting the amount of vitamin D3 you get from supplements will decrease the likelihood that you'll become constipated or develop other side effects.