What is a vitamin D test called?

The vitamin D blood test is usually called a 25-hydroxyvitamin D test, or 25(OH)D test. It measures the main circulating form of vitamin D and helps a clinician assess whether your level is within the expected range.

You may see the test written as vitamin D, 25-OH vitamin D, or 25-hydroxyvitamin D on a laboratory request or result. These names generally refer to the same assessment. A result is interpreted alongside your symptoms, medical history, medicines, sun exposure, diet, and other laboratory findings. A low result can support a diagnosis of Vitamin D Deficiency, but a result alone does not explain every symptom.

Ask the clinic which test has been ordered and whether any other blood tests will be taken at the same visit. Follow the laboratory's preparation instructions, and tell the clinician about vitamin D products or medicines you use. Do not start a high-dose supplement simply because you feel tired or have aches; the appropriate plan depends on your result and health history. Read more about the Vitamin D Test and Vitamin D Supplementation when discussing next steps.

Arrange a clinical review if persistent bone pain, muscle weakness, or marked tiredness is affecting daily activities, because these symptoms can have several causes. Seek urgent care for severe weakness, confusion, fainting, chest pain, or difficulty breathing. A vitamin D test is not an emergency test for sudden, severe symptoms.

Which form of vitamin D is being measured? What does my result mean in the context of my symptoms? Could another condition or medicine affect the result? If treatment is advised, when should the level or symptoms be reviewed?