Vitamin A test

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Blood test

This is a test to measure the amount of vitamin A (see also beta-carotene) in the blood.

Retinol test

Adult or child:

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. The band is then removed to restore circulation. After blood has been collected the needle is removed, and the puncture site is covered to stop any bleeding.

For an infant or young child, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

Fast for 4 hours before the test.

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

To investigate the possibility of vitamin A deficiency or excess, both of which are rare in the developed world.

Review Date: 03/02/2006
Reviewed By: Daniel R. Alexander, M.D., Department of Internal Medicine, St. Mary's Hospital, Leonardtown, MD. Review provided by VeriMed Healthcare Network.