Folic acid can be measured in the liquid portion of blood (plasma). 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 plasma 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 each day. It is a more
accurate way to measure the body's level of folic acid.
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
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.
Why It Is Done
A folic acid test may be done to:
anemia. A folic acid test is often done at the same
time as a test for
vitamin B12 levels because a lack of either vitamin
may cause anemia.
Check for malnutrition or problems absorbing
(malabsorption) folic acid.
See if treatment for folic acid
deficiency or vitamin B12 deficiency is working.
See if a woman has
enough folic acid to prevent certain birth defects and allow her baby to grow
How To Prepare
For the folic acid plasma 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.
How It Is Done
The health professional drawing blood
Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.
Clean the needle site with
Put the needle into the vein. More than one needle stick
may be needed.
Attach a tube to the needle to fill it with
Remove the band from your arm when enough blood is
Put a gauze pad or cotton ball over the needle site as
the needle is removed.
Put pressure on the site and then put on a bandage.
How It Feels
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
There is very little chance of a problem from
having a blood sample taken from a vein.
You may get a small bruise at the site. You can lower the chance
of bruising by keeping pressure on the site for several minutes.
rare cases, the vein may become swollen after the blood sample is taken. This
problem is called phlebitis. A warm compress can be used several times a day to
Ongoing bleeding can be a problem for people with bleeding
disorders. Aspirin, warfarin (such as Coumadin), and other blood-thinning medicines can
make bleeding more likely. If you have bleeding or clotting problems, or if you
take blood-thinning medicine, tell your doctor before your blood sample is
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.
High levels of folic acid in the blood may
mean that you eat a diet rich in folic acid, take vitamins, or take folic acid
pills. Consuming more folic acid than the body needs does not cause
High folic acid levels can also mean a vitamin B12
deficiency. Body cells need vitamin B12 to use folic acid. So if vitamin B12
levels are very low, folic acid can't be used by the cells, and high levels of
it may build up in the blood. But a folic acid test is not a reliable way to
test for a vitamin B12 deficiency.
Fischbach FT, Dunning MB III, eds. (2009).
Manual of Laboratory and Diagnostic Tests, 8th ed.
Philadelphia: Lippincott Williams and Wilkins.
How this information was developed to help you make better health decisions.