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Blood test
Blood test

Beta-carotene
Definition:
A test that measures the amount of beta-carotene in blood (see also Vitamin A test). Beta-carotene is the precursor to Vitamin A.

Alternative Names:
Carotene

How the test is performed:
Adult or child:
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

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. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
How to prepare for the test:
Fast for 6 hours before the test. The health care provider may advise you to not take potentially interfering drugs, including Vitamin A (retinol).

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
How the test will feel:
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.
Why the test is performed:
Beta-carotene levels may be measured when a Vitamin A deficiency is suspected, because Beta-carotene is metabolized to Vitamin A in the body.

Beta-carotene is also measured as an indirect measure of lipid (fat) absorption, because it is a fat-soluble nutrient.
Normal Values:
The normal range is 60 to 200 mcg/dl.

Note: mcg/dl = micrograms per deciliter
What abnormal results mean:

Abnormal results will show lower-than-normal or elevated levels.

Lower-than-normal levels may indicate a diet inadequate in beta-carotene or a problem with intestinal absorption of fat-soluble substances (termed steatorrhea).

Elevated levels may indicate hypervitaminosis A (excessive Vitamin A causing headaches, yellow skin, loss of appetite, nausea, diarrhea, dry and itchy skin, hair loss, bone pain, and cessation of menstruation in women). During pregnancy, an excess of Vitamin A can cause birth defects.
What the risks are:
  • excessive bleeding
  • fainting or feeling light-headed
  • hematoma (blood accumulating under the skin)
  • infection (a slight risk any time the skin is broken)
  • multiple punctures to locate veins
Special considerations:

While this test is a valuable test in the diagnosis of Vitamin A deficiency, the diagnosis requires interpretation of this laboratory result in conjunction with other clinical findings.

Beta-carotene is a precursor to Vitamin A in the body. Vitamin A is a fat-soluble vitamin found primarily in fish, dairy products, and green and yellow vegetables. Vitamin A is essential for normal growth, regulation of metabolism, vision, cell structure, strong bones and teeth, healthy skin, and protecting the linings of the digestive, respiratory, and urinary tracts from infection.

Signs of Vitamin A deficiency include:

Beta-carotene also functions as a fat-soluble antioxidant, that is, it may help protect the body from deleterious "free-radical" reactions.

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.
Review Date: 3/14/2002
Reviewed By: Michael C. Milone, M.D., Ph.D., Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
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