Serum or plasma concentration of vitamin D (25-hydroxyvitamin D)

Why is this test done?

Your healthcare provider may order this test if you have symptoms of vitamin D deficiency, such as fatigue, muscle weakness, or bone pain. It may also be done to check for conditions like osteoporosis, rickets, or other metabolic bone diseases. Additionally, it can be used to monitor vitamin D levels in people who take vitamin D supplements or have conditions that affect vitamin D absorption, such as celiac disease or kidney problems.

What does the test involve?

A small blood sample is taken from a vein in your arm. The blood is sent to a lab, where it is processed to separate serum or plasma. The lab then measures the amount of 25-hydroxyvitamin D, a form of vitamin D that circulates in your blood and reflects your overall vitamin D status.

What do results mean?

Results are typically reported in nanograms per milliliter (ng/mL) or picomoles per liter (pmol/L). Lower levels may indicate a deficiency, while higher levels might suggest excess intake or certain medical conditions. Your results will be interpreted by your healthcare provider in the context of your overall health and symptoms.

Common reasons for testing

Common reasons include diagnosing or monitoring vitamin D deficiency, evaluating symptoms like bone pain or frequent infections, assessing risk for conditions like osteoporosis, or checking vitamin D levels in people with certain medical conditions or those taking supplements.