CASE SCENARIO

A 65-year-old, health-conscious man reports that he eats organic food and exercises regularly. He often asks his family physician for blood tests to assess for “silent abnormalities.” He applies sunscreen whenever he goes outdoors, and at his wellness visit, he asks for a vitamin D test after reading that sunscreen blocks its production in the skin. He takes 1,000 IU of vitamin D₃ as part of a daily multivitamin. His 25-hydroxyvitamin D level is 11 ng per mL (27 nmol per L). Although his primary care physician informed him that levels greater than 8 ng per mL (20 nmol per L) are considered adequate for 97.5% of the population, the patient decided to increase his daily vitamin D dose to 5,000 IU and insisted on more frequent checks, every 4 months, until the levels exceed 20 ng per mL (50 nmol per L).

His physician explained that high vitamin D levels can be dangerous and that his current dose and level were more than adequate. The patient consulted another clinician who agreed to continue his preferred testing schedule. When the patient presented to his primary care physician 1 year later, he was taking 10,000 IU of vitamin D per day, and his 25-hydroxyvitamin D level was 34 ng per mL (85 nmol per L).