What increases my risk of vitamin D deficiency?

The Institute of Medicine (IOM) defines people as being at risk of vitamin D deficiency when their 25-hydroxy vitamin D, or 25(OH) D, blood level of is less than 30 nanograms per milliliter (ng/mL).

Some factors increase your risk of deficiency. Vitamin D in the body is either ingested as food or made during the skin's exposure to sun. As you age, your skin's ability to produce vitamin D in the skin after exposure to sunlight declines, and if you get little or no sun exposure you're at risk. People with a medical condition that impairs vitamin D absorption, such as celiac disease, Crohn's disease, or surgical removal of any portion of the stomach or small intestine, also are more likely to be deficient.