For patients with low vitamin D levels, I have been prescribing weekly supplements containing 50,000 units of vitamin D along with their usual daily OTC calcium + D tablets. Can patients be kept on this regimen year round? How often should vitamin D levels be checked in follow-up? Is there a particular calcium + D supplement you recommend?
—Jonathan Marsh, MD, Indianapolis
On a related note, is there any advantage to prescribing five drops of calciferol 200 IU/drop instead of vitamin D3 at 1,000 IU?
—Charles A. Mauriello, DO, Villanova, Pa.
The safe upper limit of vitamin D intake in adults appears to be 4,000 IU a day, or 28,000 IU weekly, so 50,000 IU of vitamin D2 (available only by prescription) weekly will eventually cause vitamin D intoxication. The most common treatment recommendation for vitamin D deficiency, i.e., 25-hydroxyvitamin D (25[OH]D) level <20 ng/mL, is 50,000 IU weekly for eight weeks. The level should be checked again a few weeks to one month after treatment. If the 25(OH)D is still <20 ng/mL, the regimen may be repeated. Once the deficiency has been treated, patients who get insufficient vitamin D from exposure to sunshine can maintain adequate levels by taking 1,000 IU of vitamin D3, which is available without a prescription. Alternatively, adequate levels may be maintained by giving 100,000 IU of vitamin D2 every three or four months. I know of no advantage (or disadvantage, for that matter) to giving five drops of calciferol 200 IU/drop compared with giving 1,000 IU of vitamin D3.
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As the primary action of vitamin D is to enhance absorption of calcium from the intestinal tract, it is very important that patients who are vitamin D-deficient take calcium as well as vitamin D. The choice of a calcium plus vitamin D supplement depends partially upon the patient. Some complain that calcium carbonate products produce gas and abdominal discomfort. Calcium gluconate is less likely to cause GI complaints. The most important factor is patient acceptability, so patients should be counseled that they may have to try a few different brands before they find one they like. Total calcium intake for those patients who get little calcium from their diets should be about 1,200-1,500 mg of calcium a day. Remember that only about 500 mg of calcium is absorbed at a time, so patients will need to divide their calcium supplements into two or three doses.
—James P. Richardson, MD, MPH (120-10)
