What it is (overview)

A Vitamin A blood test measures the amount of vitamin A in your bloodstream—most commonly retinol, the main circulating form of vitamin A. Vitamin A is a fat-soluble nutrient that supports vision (especially night vision), a healthy immune system, skin and mucosal lining health, and normal growth and development. Because vitamin A is stored in the liver and carried in the blood by proteins, blood levels can help your clinician evaluate nutritional status and identify suspected vitamin A deficiency or, less commonly, vitamin A toxicity (excess).

Results are typically reported as a concentration in the blood. In plain language:

Low vitamin A may suggest your body doesn’t have enough available vitamin A. This can happen with poor dietary intake, problems absorbing fat (since vitamin A is fat-soluble), certain liver conditions, or increased needs (for example in young children). Low levels can be associated with symptoms like night blindness, dry eyes, frequent infections, and poor growth.

High vitamin A can occur from taking too much vitamin A through supplements or medications (retinoids) rather than from food alone. Excess vitamin A can cause symptoms such as headaches, nausea, dizziness, skin changes, bone pain, and—especially important—can be harmful during pregnancy. Your clinician interprets your number alongside your symptoms, diet, supplement use, and other lab results.

When & why it's usually done

Doctors commonly order a vitamin A test when there are signs, symptoms, or risk factors for an imbalance—either deficiency or excess. It is not always part of routine screening; it is typically used when there is a clinical reason to check.

Your clinician may recommend this blood test if you have symptoms that could be related to low vitamin A, such as:

Vision-related symptoms (trouble seeing in dim light/night blindness, dry eyes), dry or rough skin, slow wound healing, or frequent infections suggesting reduced immune function.

It may also be ordered when there are reasons your body may not absorb or store vitamin A properly, including:

Malabsorption or digestive conditions (such as chronic diarrhea, inflammatory bowel disease, celiac disease, or pancreatic problems), a history of bariatric surgery, or diets very low in fat or overall calories. Because vitamin A is fat-soluble, conditions that interfere with fat absorption can increase deficiency risk.

Liver or biliary disorders may also prompt testing because vitamin A is stored in the liver and requires normal bile flow for absorption.

The test can be especially relevant in children when there are concerns about inadequate nutrition, poor growth, recurrent infections, or limited dietary variety. It may also be used to monitor patients taking high-dose vitamin A or retinoid-based treatments, or those using multiple supplements where accidental over-supplementation is possible.

Common diseases related to it

• Vitamin A deficiency (hypovitaminosis A)
• Vitamin A toxicity / hypervitaminosis A (often from supplementation)
• Xerophthalmia (dry eye disease related to severe deficiency)
• Night blindness (nyctalopia) related to deficiency
• Malabsorption syndromes (e.g., celiac disease, inflammatory bowel disease)
• Chronic pancreatitis or pancreatic insufficiency
• Cholestatic liver disease and other liver disorders affecting storage/transport
• Protein-energy malnutrition and other nutritional deficiencies

Health goals where it may help

• Assessing overall nutrition status and dietary adequacy
• Supporting healthy vision (including night vision) by identifying deficiency early
• Supporting immune system health in people with frequent infections
• Guiding safe supplementation and avoiding excessive vitamin A intake
• Monitoring nutrition in children at risk for deficiency (diet limitations, poor growth)
• Evaluating fat-soluble vitamin status in people with suspected malabsorption
• Supporting liver and digestive health evaluation when storage/absorption issues are suspected