Vitamin A (retinol)
A fat-soluble vitamin essential for vision (especially night vision), immune function and healthy skin. Deficiency is rare where diet is good but a major cause of preventable blindness worldwide, and too much from supplements is toxic — so both ends matter.
What it measures
Vitamin A (retinol) is a fat-soluble vitamin crucial for vision — particularly seeing in dim light — as well as for a healthy immune system, skin, and normal growth and development. It comes from animal foods (as retinol) and from colourful fruit and vegetables (as beta-carotene, which the body converts). Because it is fat-soluble, absorbing it depends on the gut handling fat properly, so deficiency in well-nourished countries usually reflects fat malabsorption (coeliac disease, pancreatic or liver disease, cystic fibrosis) rather than diet; globally, dietary deficiency is a leading cause of preventable childhood blindness and increased infection. The classic early sign of deficiency is difficulty seeing at night. At the other extreme, vitamin A is toxic in excess: high-dose supplements (or, rarely, huge intake of liver) cause headaches, skin and liver problems and raised pressure around the brain, and — critically — excess vitamin A in early pregnancy can harm the developing baby, which is why supplements are used cautiously.
What a high value can mean
- Excess supplementation — the commonest cause; high-dose vitamin A or retinol supplements.
- Vitamin A toxicity — headaches, dry skin, hair loss, liver problems, raised pressure around the brain.
- In pregnancy — excess vitamin A is a recognised risk to the developing baby. A high level is almost always from supplements, not ordinary diet.
What a low value can mean
- Fat malabsorption — the commonest cause in well-fed populations: coeliac disease, pancreatic or liver disease, cystic fibrosis.
- Dietary deficiency — a major global cause of preventable blindness and infection risk, especially in children.
- Early signs — difficulty seeing in dim light (night blindness), dry eyes, frequent infections.
When to discuss with a doctor
Vitamin A is not a routine test. It is worth checking when there are suggestive features — night vision problems, dry eyes, or frequent infections — especially in someone with a condition causing fat malabsorption (coeliac, pancreatic or liver disease), where deficiency can be corrected. Equally, it is relevant when vitamin A toxicity is suspected from high-dose supplements. In pregnancy, avoiding excess vitamin A (including high-dose supplements and liver) is important because of the risk to the baby — a reason to check supplement contents with a doctor or pharmacist. Mediora.AI shows vitamin A with albumin and related nutrients so the level is read in context; the interpretation and any supplementation belong with your doctor.