Vitamin D supplements may interact with certain medications. Corticosteroids (eg, prednisone) may reduce calcium absorption and hinder vitamin D metabolism. Long-term use may lead to bone loss and osteoporosis.
Serum 25-hydroxyvitamin D concentrations and health effects are as follows:
< 12 ng/mL: Associated with rickets in younger individuals and osteomalacia in adults
12-19 ng/mL: Considered inadequate for bone and overall health in most individuals
≥ 20 ng/mL: Considered adequate for health
60 ng/mL: Safe upper limit (toxic levels > 150 ng/mL)
Vitamin D may play a role in the prevention and treatment of type 1 and type 2 diabetes. However, much of this evidence is not derived from randomized clinical trials. The VITAL clinical trial found that vitamin D supplementation did not significantly reduce major cardiovascular events or all-cause mortality in middle-aged and older adults.
Sun exposure does not lead to vitamin D toxicity. Vitamin D toxicity due to food consumption is also highly unlikely. Toxicity is most likely to occur from high intakes of dietary supplements.
Read more about vitamin D.
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Cite this: Mary L. Windle. Fast Five Quiz: Vitamins - Medscape - Jan 30, 2019.