A recent article in the medical journal Cortland Forum indicated that most doctors do not properly test for vitamin D levels. They mistakenly order 1,25(OH)2D levels, as this is the active form of the vitamin. But this level can be normal or even elevated in vitamin D deficiency. The request must specify “Serum 25(OH) Vitamin D.” This is the best measure of vitamin D activity. The normal range is 20-100, but the authors indicated that anything less than 30 needs to be treated. Calcium absorption rises with increasing 25(OH)D levels. They recommended 50,000 IU of vitamin D3 orally once a week for 8 weeks, after which you may return to a “maintenance” dose of 1200-2000 IU/day. (D3 is the most important form of D.) To put this in perspective, most vitamin D supplements available over the counter contain between 400-1000 IU of D. 50,000 IU Vitamin D3 pills are available by prescription. Improvement is usually noted within 3-6 months.