If your doctor has asked for a vitamin D test, the result will help them assess your vitamin D level or see how it has changed since earlier treatment. The test commonly measures 25-hydroxyvitamin D. Let your clinician know if you take supplements and how long you have been taking them, so they can consider that information when reviewing your report.

The laboratory needs a blood sample for this test. If you are having other tests at the same visit, confirm whether any of them require special preparation. When you get your report, check which form of vitamin D was measured and bring the full report to your clinician. Your doctor can explain the result and, if you are already being treated, tell you whether and when a repeat test would help assess how your level has changed.