What it measures
The test measures retinol, the main form of vitamin A circulating in the blood. The liver stores most of the body's vitamin A and releases it bound to a carrier protein, so blood levels stay fairly steady until stores are very low or very high.
Why people test it
- Measured when poor absorption of fats is suspected, for example with coeliac disease, cystic fibrosis or after gut surgery.
- Checked in people taking high doses, since too much vitamin A can be harmful.
- Looked at when problems seeing in dim light raise the question of low vitamin A.
Typical range
Ranges vary by lab, method, age and sex, and your report shows the lab's own range. One NHS trust gives 0.99 to 3.35 µmol/L for women and 0.77 to 3.95 µmol/L for men. Source: Worcestershire Acute Hospitals NHS Trust: Vitamin A.
Finger-prick or vein?
Taken from a vein. Providers offer it only as a vein draw, at a clinic or with a visiting nurse.
Some labs ask for vitamin supplements to be stopped for two days before the sample.
· 750 servings · 3.75 mg a serving