25-Hydroxyvitamin D — written 25(OH)D — is the form of vitamin D that circulates in your blood, and the number a clinician measures to judge your vitamin D status. It reflects everything you get from sun, food and supplements combined, which makes it the single best marker of whether you are getting enough. Levels below roughly 50 nmol/L (20 ng/mL) are generally considered insufficient, and they respond directly to oily fish, fortified foods, sensible sun exposure and supplementation.
Compounds that influence 25-Hydroxyvitamin D
Written by the Nutrition Encyclopedia team · medically reviewed by Dr. Sunaina Tariq, MBBS
Last updated 22 June 2026
How we source & verify data · Medical disclaimer
Nutrition values are approximations compiled from public food-composition databases (USDA FoodData Central) and are provided for educational purposes only — not medical advice.
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