Why it is common despite the sun
Indoor lifestyles, covered skin, darker skin, air pollution and limited food sources all reduce vitamin D, even in a sunny country.
What vitamin D does
It helps the body absorb calcium and keeps bones and muscles healthy.
Who should be tested?
Testing every healthy person is not usually needed. It is most useful for people with:
- Osteoporosis or fractures from minor falls
- Bone pain or muscle weakness
- Kidney or liver disease, or conditions that affect absorption such as coeliac disease
- Long-term use of medicines that affect vitamin D, such as some anti-epileptics
- Abnormal calcium levels
What the levels mean
The test measures 25-hydroxy vitamin D. Many guidelines call a level below 20 ng/mL (50 nmol/L) deficient, though cut-offs vary.
Treatment
The dose and duration depend on the level, the cause and your other conditions, and should be set by your doctor. Getting enough calcium from food matters too. Very high doses taken without supervision can raise blood calcium and cause kidney stones.
The level is usually rechecked after about three months of treatment.
When to see a specialist
Consider an opinion if your level stays low despite treatment, or you also have abnormal calcium, kidney stones, fractures or bone pain.
This guide is general information and is not a substitute for a consultation.