Blood Test Guide

Vitamin A (Retinol) Test

Name: Vitamin A Blood Test: Normal Range & Deficiency
Creator: Suman Konda
Published: 2026-07-05

Vitamin A is essential for vision, immune function and skin health. A simple blood test measures your retinol level: find out what normal and abnormal results mean.

Written and clinically reviewed by Suman Konda, PharmD, Clinical Pharmacist · Editorial policy · Not medical advice

Last reviewed and updated: 01 August 2026 · How we check our content

Vitamin A (Retinol) reference ranges

Group	Normal Range	Unit
Adults	30–80	mcg/dL (1.05–2.80 µmol/L)
Children (1–12 yrs)	20–50	mcg/dL
Deficiency	<20	mcg/dL (<0.70 µmol/L)
Toxicity (hypervitaminosis A)	>100	mcg/dL

What is the Vitamin A blood test?

Serum Retinol

Vitamin A is measured as retinol in blood serum. The test is ordered when deficiency is suspected (night blindness, dry skin, recurrent infections) or when toxicity is a concern, for example, in people taking high-dose Vitamin A supplements or isotretinoin for acne. Because Vitamin A is fat-soluble and stored in the liver, levels reflect months of intake rather than a single meal. The test requires a fasting sample in some labs.

Symptoms of Vitamin A deficiency

Symptom	Explanation
Night blindness	Earliest sign: difficulty seeing in dim light
Dry, rough skin (xerosis)	Vitamin A maintains skin cell turnover
Bitot's spots	Foamy white patches on the white of the eye
Recurrent infections	Vitamin A is critical for immune cell function
Poor wound healing	Reduced collagen synthesis without adequate Vitamin A
Infertility	Vitamin A is needed for reproductive function

Vitamin A toxicity (hypervitaminosis A)

Can you have too much Vitamin A?

Yes. Unlike water-soluble vitamins, excess Vitamin A is stored in the liver and can accumulate to toxic levels. Toxicity is almost always caused by over-supplementation (not food). Symptoms include headache, nausea, dizziness, blurred vision, bone pain, hair loss and, in severe cases, liver damage. Pregnant women must be especially careful: excess Vitamin A is teratogenic and can cause birth defects. Do not take more than the recommended dose without medical supervision.

Causes of low Vitamin A

Cause	Mechanism
Poor dietary intake	Deficiency in foods rich in retinol (liver, dairy) and beta-carotene (orange/yellow vegetables)
Fat malabsorption	Vitamin A is fat-soluble: coeliac disease, Crohn's, cystic fibrosis reduce absorption
Liver disease	Liver stores and processes Vitamin A: cirrhosis impairs storage and conversion
Zinc deficiency	Zinc is needed to mobilise Vitamin A from the liver
Chronic infection / parasites	Infections increase Vitamin A utilisation

Questions to ask your doctor

Is my night vision poor: could that be a Vitamin A deficiency?
Do I have a fat malabsorption condition that affects Vitamin A?
Is my Vitamin A supplement dose safe?
If I am pregnant, is my Vitamin A intake within safe limits?

Frequently asked questions

Why does my lab's Vitamin A range differ from the one shown here?

Every laboratory sets its own reference interval from the analyser, reagents and reference population it uses, so two labs can publish different Vitamin A intervals and both be correct, even reporting in the same µmol/L. Read your result against the range printed on your own report.

Should a borderline Vitamin A result be repeated?

Usually. A value just outside the interval is common in people who are entirely well, since about one in twenty healthy results falls outside any 95% reference range by construction. A borderline Vitamin A is normally rechecked rather than acted on.

How soon should Vitamin A be rechecked after an abnormal result?

It depends on how abnormal the value was and why it was ordered, from days for a markedly abnormal result to months for routine monitoring. If no interval was given, that is worth asking rather than assuming.