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.¹

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.

References

Sources cited on this page. PubMed links open the original abstract.

Sommer A, West KP Jr. Vitamin A Deficiency: Health, Survival, and Vision. New York: Oxford University Press; 1996. PMID 8625773

Why vitamin A testing is less common than you might expect

Unlike vitamin D or B12, vitamin A deficiency is rare in high-income countries, so routine testing is not part of standard blood panels. In the UK and USA, clinical vitamin A deficiency is almost exclusively seen in patients with malabsorption syndromes – Crohn's disease, coeliac disease, short bowel syndrome, chronic pancreatitis, or cystic fibrosis – and in people who have undergone bariatric surgery without adequate fat-soluble vitamin supplementation.

Global public health is a different story: vitamin A deficiency remains a leading cause of preventable blindness in children in sub-Saharan Africa and South Asia, where WHO estimates approximately 250,000–500,000 children become blind each year, half of whom die within 12 months. International supplementation programmes have reduced this toll, but it remains a major burden.

What serum retinol actually measures – and its limits

The standard test measures serum retinol (the circulating form of vitamin A). A level below 0.70 µmol/L (20 µg/dL) indicates marginal deficiency; below 0.35 µmol/L (10 µg/dL) indicates severe deficiency. However, serum retinol is homeostatically regulated by the liver and remains within normal range until liver stores are substantially depleted – meaning a normal result does not exclude early insufficiency.

Retinol-binding protein (RBP) is often measured alongside retinol. Because RBP is a negative acute-phase reactant, both RBP and retinol fall during inflammation or infection regardless of true vitamin A status – so results must be interpreted in the context of CRP or other inflammatory markers.

Toxicity: the other side of vitamin A

Because vitamin A is fat-soluble and stored in the liver, excess intake causes toxicity (hypervitaminosis A). Chronic toxicity – from high-dose supplements or liver-rich diets (polar bear liver is the extreme historical case) – causes liver damage, hypercalcaemia, bone pain, hair loss, and raised intracranial pressure. Acute toxicity causes headache, nausea, and vertigo. Teratogenicity is a major concern: isotretinoin (a vitamin A derivative used in acne) and high-dose vitamin A supplements during pregnancy are contraindicated in the first trimester because of severe fetal malformation risk. The upper tolerable intake for adults is 3,000 µg RAE/day (10,000 IU/day).