1. Measure serum 25(OH)D
A. If <10 ng/ml (true deficiency), definitely start treatment.
B. If 10-20 ng/ml, probably start treatment.
C. If 20-30 ng/ml, possibly start treatment.
2. For clinically significant vitamin D deficiency
A. 50,000 IU vitamin D per week for 8-12 weeks.
B. Measure 25(OH)D to assess efficacy.
i. If 25(OH)D still very low, consider evaluating the patient for malabsorption of vitamin D. Also consider alternate methods of measuring 25(OH)D particularly if initial measurement was by standard platform immunoassay.
ii. If 25(OH)D has reached the serum 25(OH)D goal (usually >25 ng/ml), then switch to maintenance therapy.
C. Maintenance therapy
i. Prescription: 50,000 IU each month or every two weeks (the latter particularly if the patient has been diagnosed with GI malabsorption as a cause for their low serum 25(OH)D).
ii. Over the counter: daily dose is controversial (see next slides) but 1000-2000 IU per day is probably safe and effective.
iii. Sunlight exposure (or even tanning booth use). This can be very useful in patients with severe malabsorption in whom oral vitamin D supplementation are not effective.
