The vitamin D blood test explained â what it measures, why GPs order it, and when Medicare rebates it in Australia.
The standard vitamin D blood test measures 25-hydroxyvitamin D (often written 25-OH-D), the stored and circulating form of vitamin D. It is the usual marker laboratories use to describe your overall vitamin D status.
A separate, specialist test measures 1,25-dihydroxyvitamin D (the active hormone form). It is used in specific situations such as some calcium disorders, and is not the test used to assess everyday vitamin D status.
In Australia, 25-hydroxyvitamin D is reported in nmol/L (nanomoles per litre).
Vitamin D is important for calcium absorption and bone health. A test may be ordered when there are clinical reasons such as:
Your GP chooses the test based on your individual circumstances.
It is a standard blood test and does not require fasting. It can be done at any time of day. Results are usually available within a day or two.
Results are reported in nmol/L. A commonly used Australian reference point is that a level of 50 nmol/L or above is generally regarded as adequate for most people, with lower levels described as mild, moderate, or severe deficiency. Some laboratories also note that targets can be higher at the end of winter.
Reference points vary between laboratories and clinical situations. Always read the reference range printed on your own report, and only the clinician who ordered the test can interpret what your result means for you.
In Australia, Medicare rebates the 25-hydroxyvitamin D test (MBS item 66833) only for specific clinical reasons listed by Medicare â for example signs or symptoms of osteoporosis or osteomalacia, certain at-risk groups, malabsorption, or monitoring of vitamin D therapy. It is not funded for general screening of people without those reasons.
The Medicare schedule fee for item 66833 is $30.05. Where your situation meets the listed criteria, many laboratories bulk-bill the test. If you do not meet the criteria, the test may not be rebated and the laboratory may charge you. Whether your circumstances meet Medicare's criteria is a decision for your GP. Medicare also sets rules on how often pathology tests can be repeated â GPs can check these on the re-testing frequency guide.
No. A vitamin D test does not require fasting and can be done at any time of day.
In Australia, 25-hydroxyvitamin D is reported in nmol/L. Some overseas reports use ng/mL, which is a different scale.
Medicare only rebates vitamin D testing (item 66833) for specific clinical reasons. If those criteria are not met, the laboratory may charge a fee. Your GP can explain whether your situation meets Medicare's criteria.