Vitamin D deficiency is the state of having inadequate amounts of vitamin D in your body, which may cause health problems like brittle bones and muscle weakness. There may be no symptoms and doctors don’t routinely...

Vitamin D deficiency — when the level of vitamin D in your body is too low — can cause your bones to become thin, brittle or misshapen. Vitamin D also appears to play a role in insulin production and immune function...

Vitamin D deficiency occurs when your body doesn't get or process adequate amounts of vitamin D. Vitamin D helps your body absorb calcium, so a deficiency can lead to osteoporosis (low bone density) and fractures...