A folic acid test measures the amount of folic acid in the blood. Folic acid is one of many B vitamins. The body needs folic acid to make red blood cells (RBC), white blood cells (WBC), and platelets, and for normal growth. Folic acid also is important for the normal development of a baby (fetus).
Folic acid can be measured in the liquid portion of blood (serum). This reflects a person's recent intake of folic acid in the diet. Folic acid is found in foods such as liver; citrus fruits; dark green, leafy vegetables (spinach); whole grains; cereals with added B vitamins; beans; milk; kidney; and yeast.
Folic acid can also be measured as the amount in the red blood cells. This test may be a better way than the serum test to measure the amount of folic acid stored in the body. The amount of folic acid in red blood cells measures the level when the cell was made, as much as 4 months earlier. This level is not usually affected by the amount of folic acid in your diet on a single day but indicates the typical amount in your diet over several months. It is a more accurate way to measure the body's level of folic acid.
Women who are pregnant or planning to become pregnant need extra folic acid to make more red blood cells and maintain normal growth of their baby. Women who do not get enough folic acid before and during pregnancy are more likely to have a child born with a birth defect, such as a cleft lip or cleft palate or a neural tube defect, such as spina bifida.
Folic acid deficiency can result in a type of anemia called megaloblastic anemia. Mild folic acid deficiency usually does not cause any symptoms. Severe folic acid deficiency may cause a sore tongue, diarrhea, headaches, weakness, forgetfulness, and fatigue.
A folic acid test may be done to:
For the folic acid serum test, do not eat or drink (other than water) for 8 to 10 hours before the test. If you take any medicines regularly, your doctor will talk to you about how to take these before the test.
You do not need to do anything before having a folic acid red blood cell test.
The health professional drawing blood will:
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of a problem from having a blood sample taken from a vein.
A folic acid test measures the amount of folic acid in the blood.
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
3–13 nanograms per millilitre (ng/mL)
7–30 nanomoles per litre (nmol/L) (SI units)
317–1422 nmol/L (SI units)
More than 160 ng/mL
More than 362 nmol/L
Reasons you may not be able to have the test or why the results may not be helpful include:
To learn more about folic acid deficiency anemia and what foods have folic acid, see the topic Folic Acid Deficiency Anemia.
Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health.
Other Works Consulted
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
ByHealthwise StaffPrimary Medical ReviewerE. Gregory Thompson, MD - Internal MedicineBrian O'Brien, MD, FRCPC - Internal MedicineAdam Husney, MD - Family MedicineMartin J. Gabica, MD - Family MedicineJoseph F. O'Donnell, MD - Hematology, OncologyElizabeth T. Russo, MD - Internal Medicine
Current as ofOctober 9, 2017
Current as of: October 9, 2017
E. Gregory Thompson, MD - Internal Medicine
& Brian O'Brien, MD, FRCPC - Internal Medicine & Adam Husney, MD - Family Medicine & Martin J. Gabica, MD - Family Medicine & Joseph F. O'Donnell, MD - Hematology, Oncology & Elizabeth T. Russo, MD - Internal Medicine
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