MedlinePlus Medical Encyclopedia: Folic acid

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Folic acid - test

Contents of this page:
Alternative names Definition How the test is performed How to prepare for the test How the test will feel	Why the test is performed Normal Values What abnormal results mean What the risks are Special considerations

Alternative names

Folate - test

Definition Return to top

A test that measures the amount of folate in the blood.

How the test is performed Return to top

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 or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins 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.

In infants or young children:
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 Return to top

Fast for 6 hours before the test. The health care provider should be notified if you are using any drugs that can affect test results, including folic acid supplements (see "Special considerations").

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:

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 Return to top

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 Return to top

This test is used to evaluate for folic acid deficiency. It can be performed on either whole blood or red blood cells, but measuring folate in red blood cells is more accurate.

Folic acid, one of the B vitamins, is necessary for synthesis of nucleotides (which are the building blocks of DNA). A deficiency of DNA synthesis can most easily be seen in rapidly-dividing cells, such as immature red blood cells. Red blood cells that are formed in the presence of insufficient folic acid have shortened life spans, are larger than normal, and have reduced ability to carry oxygen.

Normal Values Return to top

The normal range is 2.7 - 17.0 ng/ml (nanograms per milliliter)

What abnormal results mean Return to top

Lower-than-normal levels may indicate:

inadequate diet
malabsorption syndrome (for example, sprue and celiac disease)
malnutrition

Additional conditions under which the test may be performed:

What the risks are Return to top

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 Return to top

Pregnancy increases the need for folic acid.

Drugs that can decrease folate measurements include alcohol, aminosalicylic acid, birth control pills, estrogens, tetracyclines, ampicillin, chloramphenicol, erythromycin, methotrexate, penicillin, aminopterin, phenobarbital, phenytoin, and antimalarials.

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.

Update Date: 6/1/2003

Updated by: Marcia S. Brose, M.D., Ph.D., Division of Hematology/Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA. Review provided by VeriMed Healthcare Network.

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