Vitamin A (retinol) is a fat-soluble vitamin crucial for vision (especially night vision), immune function, cell differentiation, and skin integrity. It exists in two dietary forms: preformed retinol (animal sources) and provitamin A carotenoids (plant sources like beta-carotene).

Vitamin A is stored in the liver, and serum levels only drop when liver stores are significantly depleted. For this reason, normal serum retinol does not necessarily rule out suboptimal stores. Conversely, excessive intake (especially from supplements) can cause toxicity since vitamin A is fat-soluble and accumulates.

Deficiency is rare in developed countries but causes night blindness, dry eyes, and impaired immunity. Toxicity causes headache, nausea, liver damage, and can be teratogenic in pregnancy.

What It Measures

Serum retinol concentration reflecting vitamin A status and liver stores.

Reference Ranges

How GATOR Tracks This

Related Biomarkers