Management of Vitamin D Deficiency Reviewed

Am Fam Physician. 2009;80:841-846. Abstract

Clinical Context

Skeletal development, bone health, and neuromuscular function all require vitamin D. There are 2 forms of vitamin D: vitamin D2 (ergocalciferol), produced by irradiating ergosterol found in yeast and plants; and vitamin D3 (cholecalciferol), found in oily fish and synthesized in the skin in response to sunlight.

Because few foods contain vitamin D2, it is difficult to maintain adequate levels of vitamin D from dietary sources alone, and humans typically obtain 90% of vitamin D from sunlight. Because milk and other foods have been fortified with vitamin D, the rickets epidemic has subsided, but vitamin D deficiency and insufficiency are still linked to other pathologic conditions affecting persons of all ages.


Study Highlights

Signs and symptoms of vitamin D deficiency develop slowly or are nonspecific.
These may include symmetric low back pain in women, proximal muscle weakness, muscle aches, and throbbing bone pain.
Vitamin D deficiency is defined as a 25-hydroxyvitamin D level of less than 20 ng/mL (50 nmol/L).
Vitamin D insufficiency is defined as a serum 25-hydroxyvitamin D level of 20 to 30 ng/mL (50 - 75 nmol/L).
To prevent vitamin D deficiency, infants and children should have vitamin D intake of at least 400 IU/day from diet and supplements.
Unless infants are ingesting at least 1 L/day (33.8 fl oz) of vitamin D-fortified formula or milk, they should receive supplementation of 400 IU/day.
Vitamin D supplementation, 400 IU/day, is recommended for all children and adolescents who do not get regular sunlight exposure, who do not consume 1 L/day or more of vitamin D-fortified formula or milk, or who do not take a daily multivitamin supplement containing at least 400 IU of vitamin D.
In adults, vitamin D supplementation of 700 to 800 IU or more per day may reduce rates of falls and fractures.
Contraindications to vitamin D supplementation include tuberculosis or other granulomatous diseases, metastatic bone disease, sarcoidosis, or Williams syndrome.
Patients with vitamin D deficiency should receive oral ergocalciferol (vitamin D2), 50,000 IU per week for 8 weeks.
Serum 25-hydroxyvitamin D levels should be checked when this 8-week course is completed, and if these levels are not at least 30 ng/mL, the most likely cause is nonadherence to therapy or malabsorption.
A second 8-week course of ergocalciferol should be given if the level is not at least 30 ng/mL. Patients with suspected malabsorption may need gastroenterologic consultation.
Once vitamin D levels normalize in patients who were deficient, patients should receive maintenance dosages of cholecalciferol (vitamin D3), 800 to 1000 IU per day from dietary sources and/or supplements.
Because vitamin D is fat soluble, toxicity may result from excessive supplementation.
Signs and symptoms of vitamin D toxicity may include headache, metallic taste, nephrocalcinosis or vascular calcinosis, pancreatitis, nausea, and/or vomiting.

Clinical Implications

The diagnosis of vitamin D deficiency is often missed because the signs and symptoms develop slowly or are nonspecific, such as symmetric low back pain, proximal muscle weakness, muscle aches, and throbbing bone pain. Diagnosis of suspected vitamin D deficiency or insufficiency is confirmed with measurement of 25-hydroxyvitamin D levels.
In older adults, vitamin D supplementation of 700 to 800 IU per day is associated with a lower risk for falls and fractures. Suggested treatment in patients with vitamin D deficiency is oral ergocalciferol, 50,000 IU per week for 8 weeks. Adults with vitamin D deficiency, except for those with malabsorption syndromes, should receive maintenance dosages of 800 to 1000 IU of vitamin D per day.