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Retinol Levels Blood Test

Last updated April 18, 2018

Approved by: Krish Tangella MD, MBA, FCAP

The Retinol Levels Blood Test determines the level of retinol in blood. It is used to diagnose retinol toxicity and deficiency.

What are the other Names for this Test? (Equivalent Terms)

  • Carotene Levels Blood Test
  • Vitamin A Levels Blood Test

What is Retinol Levels Blood Test? (Background Information)

  • Retinol is one of the forms of vitamin A. It is a hormone precursor and a visual pigment of the eye. Retinol is made from beta-carotene (or ß-carotene) in the liver
  • Beta-carotene is obtained through the diet. Foods rich in beta-carotene include carrots and sweet potatoes. Beta-carotene gives these foods their color
  • After the body turns beta-carotene to retinol, retinol is converted to retinal. Retinal controls the response of eye cells to light. It helps send signals to the brain for processing of visual information
  • Retinal can further be converted to retinoic acid (RA), a hormone. RA affects nearly all cells in the body, regulating their production of proteins needed for growth and differentiation into other cells
  • Retinoic acid is especially important to the growth of epithelial cells such as those in the skin and mucous membranes
  • The various forms of vitamin A, including retinol, are fat-soluble. This means that they are not excreted through urine like other vitamins, such as vitamins C and vitamin B complex, but are instead stored in the liver
  • The liver releases vitamin A bound to carrier proteins. These include prealbumin, also called transthyretin, and retinol-binding protein
  • Vitamin A is stored in the body and hence, it is easier to exceed healthy levels. Often times, this occurs due to supplementation with fish oil and other products. It can result in nausea and fatigue
  • The Retinol Levels Blood Test determines the level of retinol in blood. It is used to diagnose retinol toxicity and deficiency

What are the Clinical Indications for performing the Retinol Levels Blood  Test?

Following are the clinical indications for performing the Retinol Levels Blood Test:

  • Night blindness
  • Rough, dry skin
  • Raised bumps on the back of the arms
  • Dry eyes
  • Stunted growth and development
  • Headache
  • Fatigue
  • Bone and joint pain
  • Dizziness
  • Drowsiness

How is the Specimen Collected for Retinol Levels Blood Test?

Following is the specimen collection process for Retinol Levels Blood Test:

Sample required: Blood

Process of obtaining blood sample in adults:

  • A band is wrapped around the arm, 3-4 inches above the collection site (superficial vein that lies within the elbow pit)
  • The site is cleaned with 70% alcohol in an outward spiral, away from the zone of needle insertion
  • The needle cap is removed and is held in line with the vein, pulling the skin tight
  • With a small and quick thrust, the vein is penetrated using the needle
  • The required amount of blood sample is collected by pulling the plunger of the syringe out slowly
  • The wrap band is removed, gauze is placed on the collection site, and the needle is removed
  • The blood is immediately transferred into the blood container, which has the appropriate preservative/clot activator/anti-coagulant
  • The syringe and the needle are disposed into the appropriate “sharp container” for safe and hygienic disposal

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the Retinol Levels Blood Test Result?

The significance of the Retinol Levels Blood Test result is explained:

  • High retinol blood levels may indicate:

    • Chronic kidney disease
    • Hypercalcemia of unknown origin in infants
    • Vitamin A toxicity   
    • Birth defects
    • Yellowing of the skin
  • Low retinol blood levels may indicate:

    • A-ß-lipoproteinemia
    • Carcinoid syndrome
    • Chronic infections       
    • Disseminated tuberculosis
    • Hypothyroidism
    • Liver, gastrointestinal, or pancreatic disease
    • Protein malnutrition
    • Sterility and teratogenesis
    • Zinc deficiency

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Certain factors, such as diet, interfere with the results of the Retinol Levels Blood Test
  • Retinol is the active ingredient in the drug tretinoin (Retin-A), which is used to treat severe acne and wrinkled skin
  • Vitamin A deficiency is common in regions where people have limited diets due to low socioeconomic levels. Though rare in the US, 190 million preschool children and 19 million pregnant women around the world are at risk for vitamin A deficiency, according to the World Health Organization (WHO)
  • Foods rich in vitamin A include fish, liver, eggs, whole milk, and butter

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

  • If abnormally excess amounts of vitamin A builds-up in the liver, due to sudden overdose of the substance, or through accumulation of small doses over prolonged periods of time, it leads to a toxic condition called hypervitaminosis A

The following article link will help you understand hypervitaminosis A:


Please visit our Laboratory Procedures Center for more physician-approved health information:


References and Information Sources used for the Article:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Sept. 13, 2015
Last updated: April 18, 2018