Vitamins and minerals
Vitamin D
This test measures 25-hydroxyvitamin D, the storage form. Vitamin D supports calcium absorption and bone health, and is made in the skin in response to sunlight as well as taken in through food and supplements.
Typical adult reference range
Roughly 30 to 100 is often described as sufficient, with deficiency below 20 · ng/mL
Ranges vary between laboratories and by age, sex and method. Always read your own result against the range printed on your own report.
What a high result can mean
Very high levels almost always come from taking large supplement doses rather than from sun or diet, and can raise blood calcium, which is why very high doses are not harmless.
What a low result can mean
Low vitamin D is extremely common, particularly in winter, at higher latitudes, with darker skin, with limited sun exposure, and with covering clothing. It can contribute to bone pain and muscle weakness, and long-standing severe deficiency affects bone strength.
What commonly affects this result
Season, latitude, skin tone, sun exposure, body weight, and supplement use.
Questions worth asking your doctor
- Is my level low enough to need treatment doses rather than a maintenance dose?
- How long should I supplement before rechecking?
- Should my calcium be checked alongside this?
See what your own results say
Upload your blood test and get a plain English summary of every value on it, with the questions worth raising at your next appointment.
Analyse my resultsThis page explains what a test measures. It is general information, not medical advice, and it cannot tell you what your own result means. Reference ranges differ between laboratories, and results are only meaningful alongside your history, your symptoms and your other results. Always discuss your results with your doctor.