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

Why is this test done? Your healthcare provider may order a vitamin D test to check whether your levels are too low or too high, which can affect bone health, immune function, and overall well-being. This test is often done if you have symptoms of deficiency, such as fatigue or bone pain, or if you are at risk due to limited sun exposure, diet, or certain medical conditions.

Your healthcare provider may order this test to check if you have enough vitamin D. Common reasons include suspected deficiency, monitoring treatment for conditions like osteoporosis or rickets, or evaluating symptoms like fatigue, muscle weakness, or frequent infections.

What does the result mean? The result of your vitamin D test shows the amount of 25-hydroxyvitamin D in your blood, which is the main form used to determine your status. A result within the normal range generally means your bones and muscles are getting enough vitamin D, while a low result may indicate deficiency that could require supplements, and a high result might suggest toxicity from excessive intake.

Results are typically reported in nanograms per deciliter (ng/dL). While reference ranges vary by lab, low levels (below typical normal) may suggest deficiency, while higher levels may indicate over-supplementation or other conditions.

What can affect your results? Several factors can affect your vitamin D test results, including your diet, use of supplements, amount of sunlight exposure, and skin pigmentation. Certain medications like steroids or weight-loss drugs, as well as kidney or liver disease, can also change how your body processes vitamin D and lead to inaccurate readings.

Several factors can influence vitamin D levels, including sun exposure, diet (e.g., fatty fish, fortified foods), obesity, liver or kidney disease, and certain medications. Recent vitamin D supplements or changes in diet may also affect results.

How is the test performed? The vitamin D test is performed by drawing a small sample of blood from a vein in your arm using a needle and a collection tube. The sample is then sent to a laboratory where it is analyzed to measure the level of 25-hydroxyvitamin D, and the entire process usually takes only a few minutes for the blood draw.

A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab for testing using an immunoassay method to measure the specific vitamin D compound in your serum or plasma.