What is the most accurate vitamin D test?

The test measures 25-hydroxyvitamin D, the main circulating form used to assess vitamin D stores. Results are interpreted against the laboratory range and your circumstances, such as bone symptoms, limited sun exposure, absorption problems, kidney or liver disease, pregnancy, and medicines. Tiredness or muscle aches alone do not establish deficiency; they can have many causes. See [Vitamin D Deficiency](/conditions/vitamin-d-deficiency/) for related information.

Ask whether you need the test and whether any supplements or medicines should be recorded before the blood draw. Do not take large doses because of a home result or a general symptom. If deficiency is confirmed, your clinician may recommend [Vitamin D Supplementation](/treatments/medical-management/vitamin-d-supplementation/) and a follow-up plan. The formal [Vitamin D Test](/treatments/diagnostics-and-screening/vitamin-d-test/) page explains the assessment.

Arrange a review for persistent bone pain, muscle weakness, repeated falls or a fracture. Seek prompt advice after excessive supplementation if you develop persistent vomiting, marked thirst, frequent urination, confusion or severe weakness. Symptoms such as widespread pain may also need assessment for other conditions, including [Fibromyalgia](/conditions/fibromyalgia/).

Ask whether 25-hydroxyvitamin D is appropriate for you, what your result means in context, whether calcium or kidney tests are needed, which dose is suitable, and when a repeat test would help.