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 bone pain, muscle weakness, or frequent infections. It may also be recommended if you have a condition that affects vitamin D absorption, like kidney disease or certain gastrointestinal disorders. Additionally, it could be part of a routine check for people at higher risk, such as older adults, those with limited sun exposure, or those with limited sun exposure or dietary habits.

What to Expect Before the Test

No special preparation is usually needed. If you’re having blood drawn, you may want to drink plenty of water beforehand to help reduce discomfort. If you’re having a urine sample taken, follow any specific instructions your provider gives you.

What Happens During the Test?

For a blood test, a healthcare professional will insert a small needle into a vein in your arm. You may feel a slight pinch or stinging. For a urine test, you’ll collect a sample in a clean container. The sample will be sent to a lab for analysis.

What Are the Possible Results?

Results will be reported as a concentration of vitamin D in your blood, measured in nanograms per milliliter (ng/mL) or picomoles per liter (pmol/L). Your provider will interpret these results in relation to your health and symptoms.