The vitamin D test measures a form of the vitamin in your blood called 25-hydroxyvitamin D. Vitamin D helps your body absorb calcium and keep bones strong. Here is how to read your result.
The most common vitamin D test measures 25-hydroxyvitamin D, the main form circulating in your blood. Vitamin D helps your body absorb calcium, which supports healthy bones, muscles, and nerves. Your skin makes vitamin D from sunlight, and you also get it from some foods and supplements.
Vitamin D is reported in either ng/mL or nmol/L, and the exact ranges a lab uses can differ. Because of that, the interpretation of a “low” or “sufficient” level should come from your report and your clinician rather than a fixed universal number. What matters is how your value reads against the range printed alongside it.
A low vitamin D level is common and can be influenced by limited sun exposure, skin tone, older age, certain medical conditions, and diet. Over time, low vitamin D can affect bone health. Your clinician decides whether a result needs action, such as diet changes or supplements, based on your overall situation.
Upload your lab report and Mednex reads your vitamin D against the range on your own document, in plain language, and tracks it over time.
Decode my labsContent last reviewed 9 July 2026. Reference ranges vary by laboratory; always read your results against the range printed on your own report.
This page explains a common lab marker in general terms using public information from the U.S. National Library of Medicine and other NIH sources. It is educational and is not a diagnosis or medical advice. Reference ranges differ between laboratories and the meaning of a result depends on your age, sex, medications, and overall health. Always discuss your own results with the clinician who ordered them.