This test measures 25-hydroxyvitamin D, the main circulating form of vitamin D and the standard way to assess your vitamin D status. Low levels are common in the UK, especially between October and March when sunlight is too weak for the skin to make enough. The test costs £108.75 plus the £50 phlebotomy fee, with results in 1 day.
No fasting is needed. If you already take a vitamin D supplement, keep taking it as usual unless a clinician has told you otherwise, so the result reflects your normal level.
Written by Mr Stephen Lingam. Reviewed by Dr Mohammad Bakhtiar (GMC 4694470) on 06/09/2026.
People with tiredness, bone or muscle aches, limited sun exposure, darker skin, or conditions that affect absorption, and anyone checking whether a supplement is working.
No. There is no fasting or special preparation for a vitamin D test.
The result is given in nmol/L. In the UK, levels below 25 nmol/L are generally considered deficient and 50 nmol/L or above adequate for most people.
Results are usually available in 1 day by email.