Vitamin A (retinol)
Fat-soluble vitamin for vision, skin and mucous membranes, measured in blood as retinol
Also known as
Definition
Vitamin A is a fat-soluble vitamin that the body stores in the liver. It enters the diet as preformed vitamin A (retinol) from animal foods or as a precursor such as beta-carotene from plants. It is needed for vision in low light and helps maintain skin, mucous membranes, teeth and bones. The blood test measures how much vitamin A is circulating in the blood.
| Parameter | Value |
|---|---|
| Unit | µg/dl or µmol/l |
| Reference Range | Typical range according to MedlinePlus: 30–120 µg/dl or 1.1–4.2 µmol/l. Labs may use slightly different ranges and methods; the range on your own report is what counts. Discuss deviations with your doctor. |
Agree on your personal target range with your doctor.
Conversion: µg/dl × 0.0349 = µmol/l; µmol/l × 28.6 = µg/dl. Converted values are rounded and may differ slightly from a lab's figures.
↓ What a low value means
A low value means there is little vitamin A in the blood. This may be related to problems absorbing fat in the gut, for example with cystic fibrosis, pancreatic conditions such as inflammation or too little enzyme production, or celiac disease. A deficiency can show up as night blindness, dry or inflamed eyes, dry and scaly skin, skin rashes, recurring infections, hair loss or loss of appetite, among others. Your doctor clarifies the cause.
↑ What a high value means
A high value means vitamin A may have built up in the body. Too much preformed vitamin A can make you ill, with bone and muscle pain, nausea, diarrhea, double vision, hair loss, coordination problems, an enlarged liver and spleen or increased pressure in the brain, among others. During pregnancy, large amounts can cause birth defects. Large amounts of beta-carotene turn the skin yellowish-orange but do not cause serious illness. Discuss raised values with your doctor.
When to test
The test is used to detect too much or too little vitamin A in the blood, for example with matching symptoms or with conditions that impair fat absorption. Depending on the lab, a fasting period of up to 24 hours may be required; follow the instructions of your practice or lab.
Frequently asked questions
What is the difference between retinol and beta-carotene? +
Retinol is preformed, active vitamin A and is found mainly in animal foods such as liver, whole milk or fortified products. Beta-carotene is a plant pigment that the body converts into vitamin A as needed. It is found, for example, in carrots, sweet potatoes or dark leafy greens.
Can beta-carotene cause vitamin A poisoning? +
According to MedlinePlus, large amounts of beta-carotene do not cause serious illness but can turn the skin yellowish-orange. This reverses when intake drops. Overdose mainly concerns preformed vitamin A, for example from supplements.
Do I need to fast for the test? +
That depends on the lab. Some require you not to eat or drink anything for up to 24 hours beforehand. Ask your practice or lab which instructions apply.
Why is vitamin A a special topic during pregnancy? +
Vitamin A plays a role in pregnancy and breastfeeding, but large amounts can cause birth defects in the unborn child. Whether and how vitamin A is checked during this time is something to discuss with your doctor.
Vitamin A (retinol)
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.