This is a test that measures the amount of beta-carotene in blood (see also Vitamin A test). Beta-carotene is the precursor to Vitamin A.
How the test is performed
Blood is drawn from a vein on 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. During the procedure, the band 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.
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. 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).
For Infants and children:
The preparation you can provide for this test depends on your child’s age and previous experience. For specific information regarding how you can prepare your child, see the following topics:
- infant test or procedure preparation (birth to 1 year)
- toddler test or procedure preparation (1 to 3 years)
- preschooler test or procedure preparation (3 to 6 years)
- schoolage test or procedure preparation (6 to 12 years)
- adolescent test or procedure preparation (12 to 18 years)
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 (broken down) 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.
The normal range is 60 to 200 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
This risks associated with having blood drawn 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
While this test is a valuable part of the diagnosis of Vitamin A deficiency, the actual diagnosis requires interpretation of the test 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. It 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:
- vision problems (inability to see at night)
- bone or teeth development problems
- unexplained irritability
- skin rashes
- hair loss
- dry or inflamed eyes
- loss of appetite
- recurring infections
Beta-carotene also functions as a fat-soluble antioxidant, that is, it may help protect the body from harmful “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.
by Sharon M. Smith, M.D.
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.