The currently accepted lower limit of 25-hydroxyvitamin D (25[OH]D) for optimal bone health is 32 ng/mL, which is higher than previously stated (Item 120-10).
—Robert Blereau, MD, Morgan City, La.
Dr. Blereau is correct: The optimal level of 25(OH)D is 32 ng/mL in most labs. Some authorities recommend levels of 40 or even higher, based on measurements made in farmers and others who work outside and get maximal sun exposure. My earlier response was focused on treating patients with vitamin D deficiency (levels <20 ng/mL), rather than insufficiency (levels between 20 and 32). Once the deficiency is treated, most patients who follow the long-term regimens I recommended (1,000 IU of D3 once a day or 100,000 IU of D2 quarterly) will become vitamin D-sufficient over the ensuing weeks. A 25(OH)D level should be checked to ensure that this occurs (and can also serve as a check on the patient’s compliance).
Although optimally, we want all our patients to attain vitamin D sufficiency, the most serious consequences of inadequate levels (e.g., osteomalacia, chronic pain, gait disorders, and falls) are far more common in those with deficiency than with insufficiency. Certainly, if the patient is willing to take repeated courses of prescription-strength vitamin D to increase his levels more quickly, all the better. I applaud Dr. Blereau’s attention to this important issue.
—James P. Richardson, MD, MPH (121-15)