Folic acid - test

Most of the time, blood is taken from a vein on 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 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.

You should not eat or drink for 6 hours before the test. Your provider may tell you to stop taking any drugs that may interfere with test results, including folic acid supplements.

Drugs that can decrease folic acid measurements include:

• Alcohol
• Aminosalicylic acid
• Birth control pills
• Estrogens
• Tetracyclines
• Ampicillin
• Chloramphenicol
• Erythromycin
• Methotrexate
• Penicillin
• Aminopterin
• Phenobarbital
• Phenytoin
• Drugs to treat malaria

You may feel slight pain or a little sting when the needle is inserted. There may be some throbbing at the site.

This test is done to check for folic acid deficiency.

Folic acid helps form red blood cells and produce DNA that stores genetic codes. Taking the right amount of folic acid before and during pregnancy helps prevent neural tube defects, such as spina bifida.

Women who are pregnant or planning to become pregnant should take at least 600 micrograms (mcg) of folic acid every day. Some women may need to take more if they have a history of neural tube defects in earlier pregnancies. Ask your provider how much you need.

The normal range is 2.7 to 17.0 nanograms per milliliter (ng/mL) or 6.12 to 38.52 nanomoles per liter (nmol/L).

Normal value ranges may vary slightly among different labs. Talk to your provider about the meaning of your test results.

The examples above show the common measurements for results for these tests. Some labs use different measurements or may test different specimens.

Lower-than-normal folic acid levels may indicate:

• Poor diet
• Malabsorption syndrome (for example, celiac sprue)
• Malnutrition

The test may also be done in cases of:

• Anemia due to folate deficiency
• Megaloblastic anemia

There is very little risk involved with having your blood taken.

Other slight risks from having blood drawn may include:

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

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Elghetany MT, Schexneider KI, Banki K. Erthrocytic disorders. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 32.

Mason JB. Vitamins, trace minerals, and other micronutrients. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 218.