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Vitamin D

Vitamin D supports healthy bone density, insulin production, and immune function. While the recommended amount of vitamin D is not generally acquired from the diet, it can be reached through exposure to sunlight and supplementation. Vitamin D deficiency can lead to increased susceptibility to infection¹. Deficiency usually affects older people who aren’t exposed to enough sunlight or don’t eat vitamin-enriched foods and increases their risk of fractures². Vitamin D toxicity—called hypervitaminosis D—occurs in those with excess vitamin D in the body but is rare and generally only caused by extreme over-supplementation. It can have serious health effects, such as kidney stones and bone issues.

This test measures blood levels of 25-hydroxyvitamin D, the best way to screen and monitor vitamin D levels.

Finding out if you have vitamin D deficiency will allow you to adjust your lifestyle and nutrition. You can increase your vitamin D level by taking supplements or by consuming more vitamin D-enriched foods.


  1. Aranow C. Vitamin D and the immune system. J Investig Med 2011;59(6):881–886.
  2. Sizar O, Khare S, Goyal A, et al. Vitamin D Deficiency. 2021 Jan 3. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID:30335299.
Last updated:
August 6, 2021

Test for vitamin D

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