Vitamin A is a fat-soluble vitamin. This article describes the test used to measure the amount of vitamin A in the blood.

See also: Beta-carotene test

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

Do not eat or drink anything 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.

This test is done to determine if you have too much or too little vitamin A in your blood. However, such conditions are rare in the developed world.

Normal values range from 50 to 200 micrograms per deciliter.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

Lower-than-normal values indicate a vitamin A deficiency, which may be associated with:

• Developmental aberrations of bones or teeth in young children
• Dry or inflamed eyes
• Hair loss
• Inadequate absorption of fats from the intestinal tract
• Loss of appetite
• Malabsorption syndrome (for example, celiac disease, sprue)
• Night blindness
• Recurring infections
• Skin rashes

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)