Deficiency, Blood Concentrations, and Toxicity
Risk factors for vitamin D deficiency include living in northern latitudes (in the U.S., above the line from San Francisco to Philadelphia), failing to get at least 15 minutes of direct sun exposure daily, being African American or dark-skinned, being elderly, or being overweight or obese. Rickets and osteomalacia are the well-known diseases of severe vitamin D deficiency. Musculoskeletal pain and periodontal disease may also indicate a significant vitamin D deficiency. Subtle symptoms of milder deficiency include loss of appetite, diarrhea, insomnia, vision problems, and a burning sensation in the mouth and throat. Drawing a blood calcidiol concentration is the standard test for vitamin D status, since calcidiol has a longer half-life.
A normal range of vitamin D is 30 to 74 ng/mL, but this can vary among laboratories. Most experts agree that a concentration between 35 and 40 ng/mL is reasonable for preventive health. Some suggest that the optimal concentration for protecting against cancer and heart disease is between 50 and 70 ng/mL and up to 100 ng/mL. Side effects or toxicity can occur when blood concentrations reach 88 ng/mL or greater. Symptoms include nausea, vomiting, constipation, headache, sleepiness, and weakness. Too much vitamin D can raise blood calcium concentrations, and acute toxicity causes hypercalcemia and hypercalciuria.[6,9]
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Cite this: Vitamin D Supplementation: An Update - Medscape - Oct 01, 2010.