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Folate Test

Test Overview

A folate test measures the amount of folate in the blood. Folate is one of many B vitamins. The body needs folate for normal growth and to make red blood cells (RBC), white blood cells (WBC), and platelets. Folate also is important for the normal development of a baby (fetus).

Folate can be measured in the liquid portion of blood (plasma). This reflects a person's recent intake of folate and folic acid in the diet. Folate is found in foods such as liver; citrus fruits; dark green, leafy vegetables (spinach); whole grains; and beans. Folic acid is the man-made form of folate. It's found in vitamin pills and fortified foods, such as fortified breakfast cereals.

Folate 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 folate stored in the body. The amount of folate 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 folate and folic acid in your diet each day. It is a more accurate way to measure the body's level of folate.

Folate deficiency can result in a type of anemia called megaloblastic anemia. Mild folate deficiency often does not cause any symptoms. Severe folate deficiency may cause a sore tongue, diarrhea, headaches, weakness, forgetfulness, and fatigue.

Why It Is Done

A folate test may be done to:

  • Check for the cause of anemia. A folate 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) folate.
  • See if treatment for folate deficiency or vitamin B12 deficiency is working.
  • See if a woman has enough folate to prevent certain birth defects and allow her baby to grow normally.

How To Prepare

For the folate 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 folate red blood cell test.

How It Is Done

A health professional uses a needle to take a blood sample, usually from the arm.

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.


There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.



Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

High values

  • High levels of folate in the blood may mean that you eat a diet rich in folate or folic acid, take vitamins, or take folic acid pills. Consuming more folate than the body needs does not cause problems.
  • High folate levels can also mean a vitamin B12 deficiency. Body cells need vitamin B12 to use folate. So if vitamin B12 levels are very low, folate can't be used by the cells, and high levels of it may build up in the blood. But a folate test is not a reliable way to test for a vitamin B12 deficiency.

Low values

  • Low folate levels can mean that you have a problem with your diet, alcohol use disorder, or an eating disorder such as anorexia nervosa.
  • Low folate levels can also mean that you have a problem absorbing or using folate, such as a vitamin C deficiency, liver disease, celiac disease, sprue, or Crohn's disease.
  • Low folate levels can cause problems for certain people. For example:
    • A pregnant woman needs extra folate for her growing baby.
    • People who have hemolytic anemia, a condition that causes the fast destruction of red blood cells, need more folate to make more red blood cells.
    • People who have certain conditions, such as kidney failure and some types of cancer, may use up folate quickly. They may need their blood to be cleaned using a machine (kidney dialysis).


Current as of: November 29, 2021

Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Martin J. Gabica MD - Family Medicine
Elizabeth T. Russo MD - Internal Medicine