A nutritional condition produced by a deficiency of VITAMIN D in the diet, insufficient production of vitamin D in the skin, inadequate absorption of vitamin D from the diet, or abnormal conversion of vitamin D to its bioactive metabolites. It is manifested clinically as RICKETS in children and OSTEOMALACIA in adults. (From Cecil Textbook of Medicine, 19th ed, p1406)

Abnormally low level of 25-hydroxyvitamin D in the blood.

Condition due to a deficiency of vitamin D.

Vitamin D deficiency means that you are not getting enough vitamin D to stay healthy. Vitamin D helps your body absorb calcium. Calcium is one of the main building blocks of bone. Vitamin D also has a role in your nervous, muscle, and immune systems. You can get vitamin D in three ways: through your skin, from your diet, and from supplements. Your body forms vitamin D naturally after exposure to sunlight. But too much sun exposure can lead to skin aging and skin cancer, so many people try to get their vitamin D from other sources. The amount of vitamin D you need each day depends on your age. The recommended amounts, in international units (IU), are Birth to 12 months: 400 IU; Children 1-13 years: 600 IU; Teens 14-18 years: 600 IU; Adults 19-70 years: 600 IU; Adults 71 years and older: 800 IU; Pregnant and breastfeeding women: 600 IU. People at high risk of vitamin D deficiency may need more. Check with your health care provider about how much you need.

(low levels of vitamin d) A reduced concentration of Vitamin D.

Vitamin D deficiency is most commonly caused by a lack of exposure to sunlight. Some disorders can also cause the deficiency. The most common cause is lack of exposure to sunlight, usually when the diet is deficient in vitamin D, but certain disorders can also cause the deficiency.