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

Why Is This Test Done?

Your doctor may order this test to check if you have enough vitamin D, which is crucial for maintaining strong bones and preventing conditions like osteoporosis. It can also help diagnose or monitor vitamin D deficiency, which may cause symptoms like fatigue, muscle weakness, or bone pain. Sometimes, it’s used to evaluate conditions like rickets in children or osteomalacia in adults.

What Does the Test Involve?

A blood sample is taken from a vein in your arm. The blood is sent to a lab where it is processed to measure the concentration of 25-hydroxyvitamin D, a form of vitamin D that reflects your overall vitamin D status.

What Are Common Results?

Results are typically reported in nanograms per milliliter (ng/mL) or picomoles per liter (pmol/L). While exact reference ranges can vary by lab, low levels may indicate deficiency, while higher levels may suggest excess intake or certain medical conditions.

What Are Possible Causes of Abnormal Results?

Low levels of vitamin D can result from insufficient sun exposure, poor diet, limited absorption in the gut, or certain medical conditions. High levels may be due to over-supplementation or rare genetic disorders.