Vitamin A testing is used to help diagnose vitamin A deficiency in people with symptoms, such as night blindness, or in people with diseases that impair intestinal absorption of nutrients. It may also be used to detect toxic levels caused by ingestion of large amounts of vitamin A.
Testing may be done when a person has a disease that is associated with malabsorption of nutrients to monitor vitamin A status. Testing may be done periodically to insure that the person is getting sufficient vitamin A. Some diseases that are associated with inadequate vitamin A absorption include:
Testing may be performed when a person has symptoms that suggest vitamin A toxicity and their medical history is consistent with consumption of foods or vitamin supplements containing vitamin A. Some of the symptoms associated with vitamin A toxicity are:
A normal vitamin A level indicates that a person currently has sufficient vitamin A but does not indicate how much is stored in reserve. The body will maintain vitamin A in the blood at a relatively stable level until stores are depleted. A low vitamin A test result indicates that all reserves have been depleted and the person is deficient.
A high vitamin A level typically indicates that the capacity to store vitamin A has been exceeded and excess vitamin A is now circulating in the blood and may be deposited in other tissue, leading to toxicity.
A person with a minimal amount of vitamin A stored may have marginal but adequate vitamin A until they have an illness or other condition, such as pregnancy, that puts increased demands on their body. This is one of the reasons that night blindness during pregnancy is prevalent in many parts of the world.
Eating excessive amounts of foods with beta carotene, such as carrots, can cause a person's skin to turn yellow-orange but it does not cause vitamin A toxicity. The body does not convert beta carotene to vitamin A when there is sufficient vitamin A present.
This article was last reviewed on May 12, 2011. | This article was last modified on May 27, 2014.
The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.
The modified date indicates that one or more changes were made to the article. Such changes may or may not result from a full review of the article, so the two dates may not always agree.