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Folate Test

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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. 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.

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, 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 the folate level is high enough to prevent certain birth defects.

How To Prepare

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.

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 lot of foods rich in folate or folic acid, take vitamins, or take folic acid pills.
  • 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 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:
    • Someone who is pregnant needs extra folate for the 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).
  • Low folate levels can mean that you aren't getting enough folate in your diet. This is usually only true for people who can't eat very much food, such as people with alcohol use disorder, certain cancers, or an eating disorder.

Related Information


Current as of: May 13, 2023

Author: Healthwise Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

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