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What is a Vitamin A test?
Also known as the Retinol test, this test measures vitamin A levels in the body. It assesses both the excess and deficiency of vitamin A.
Vitamin A is mainly stored in the fat tissues and liver. It is necessary for:

  • Development of bones
  • Proper functioning of the immune system
  • Production of photoreceptors in eyes
  • Maintaining the integrity of skin
  • Maintaining the lining of mucous membranes, like the surface of eyes
  • Maintaining a healthy vision

Vitamin A deficiency is very rare. It is mostly caused by long periods of inadequate amount of vitamin A in the diet. However, it can also happen due to fat malabsorption or liver disorder. In the elderly, chronic alcoholism can also lead to vitamin A deficiency. One of the earliest and serious manifestations of which is night blindness.

  1. Why is a Vitamin A test performed?
  2. How do you prepare for a Vitamin A test?
  3. How is a Vitamin A test performed?
  4. What do Vitamin A test results indicate?

This test is usually ordered for people who show apparent symptoms of vitamin A deficiency.
Vitamin A deficiency is primarily observed in older people and people with malabsorption disorders, such as pancreatitis, celiac disease, cystic fibrosis, and other conditions, like alcoholism.
The test may be recommended for people who are at risk of having vitamin A deficiency, such as pregnant women and preschool children.

Symptoms of vitamin A deficiency are as follows:

  • Conjunctival xerosis (the first clinical sign of vitamin A deficiency)
  • Night blindness or inability to see in dim light
  • Bitot’s spots
  • Corneal xerosis
  • Corneal scarring
  • Keratomalacia or liquefaction of the cornea, which is considered to be a medical emergency

Furthermore, a retinol test is performed when vitamin A toxicity signs are suspected. Various toxicity manifestations are as follows: 

Vitamin A toxicity primarily occurs due to excess consumption of vitamin A supplements. In some cases, it occurs when the diet includes foods that are high in vitamin A.

You'll have to be on fast for 24 hours before the test (eating and drinking needs to be avoided altogether). There should be no prior alcohol consumption, as it can lead to abnormally high values of vitamin A. Make sure that you inform your doctor about any current medications and/or allergies, if present. Based on the information provided, the doctor will give specific instructions on how to prepare for the test.

A blood sample is collected from a vein in the arm for this test. 

  • A phlebotomist or technician will tie a rubber band around your upper arm
  • Once a vein is visible, he/she will clean the area from where the blood is to be withdrawn
  • A needle will then be inserted in the vein to collect a blood sample. This can lead to slight stinging pain
  • Once enough blood is withdrawn, the needle will be pulled out and a band-aid will be placed at the site of blood withdrawal

You will be asked to press the site firmly to stop the bleeding. After the test, some patients experience slight throbbing and bruising, which will soon go away. 

Normal results:
Normal value of vitamin A ranges from 50 to 200 mg/dL. Though different laboratories might use different measurements. Consultation with a doctor is necessary to know the accurate meaning of results.

Abnormal results:
Values less than the normal range indicate a deficiency of vitamin A, which can be due to inadequate amounts of the vitamin in your food or decreased absorption from the food.
Values above the normal range indicate toxicity.
Abnormal low values of vitamin A can be seen in the following conditions:

  • Pancreatitis (inflammation of the pancreas)
  • Liver disorders
  • Cystic fibrosis (a life-threatening genetic condition that can damage the digestive system and lungs)
  • Celiac disease (an immune reaction to the consumption of gluten)
  • Chronic alcoholism

Abnormal high values of vitamin A can be seen in the following conditions:

  • Vitamin A supplementation
  • Excessive intake of vitamin A-rich food, like fish

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

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References

  1. Beaufort Memorial Hospital. [Internet] SC, U.S.Vitamin A blood test
  2. UCSF health. [internet] University of California.Vitamin A Test
  3. MedlinePlus Medical Encyclopedia. [Internet] US National Library of Medicine; Hypervitaminosis A
  4. National Institute on Alcohol Abuse and Alcoholism. [Internet] National Institute of Health U.S; Relationships Between Nutrition, Alcohol Use, and Liver Disease
  5. MedlinePlus Medical Encyclopedia. [Internet] US National Library of Medicine; Vitamin A blood test
  6. ARUP Consult, ARUP Laboratories.[Internet] Salt City, UT, U.S.Vitamin A (Retinol), Serum or Plasma
  7. Clare Gilbert. The eye signs of vitamin A deficiency Community Eye Health. 2013; 26(84): 66–67 PMID: 24782581
  8. Johns Hopkins Medicine [Internet]. The Johns Hopkins University, The Johns Hopkins Hospital, and Johns Hopkins Health System; Blood Test