A folic acid test measures the amount of folic acid in the blood. Folic acid is vitamin B-9, which is essential for the production of healthy red blood cells. These cells deliver oxygen to the entire body, so they’re vital for maintaining overall health. Folic acid is also important for the normal development of a fetus. It helps with cell and tissue growth as well as the creation of DNA, which carries genetic information. This is why folic acid is particularly critical for women who are pregnant or who are planning to become pregnant.
According to the Centers for Disease Control and Prevention (CDC), women should take 400 micrograms of folic acid every day, starting at least one month before getting pregnant. Taking extra folic acid during pregnancy can help prevent brain and spinal cord birth defects, such as spina bifida and a cleft lip or cleft palate.
While there are folic acid supplements, the vitamin is also naturally found in several foods, including:
- citrus fruits
- whole grains
- dark green, leafy vegetables, such as spinach and kale
- bok choy
- Brussels sprouts
- fortified cereals
If you aren’t consuming enough folic acid, you may develop a folic acid deficiency. While mild folic acid deficiency usually doesn’t trigger symptoms, severe folic acid deficiency can cause diarrhea, fatigue, and a sore tongue. The deficiency may also lead to a more serious condition known as anemia, which is caused by a lack of healthy red blood cells.
Since folic acid levels can be measured in the bloodstream, a folic acid test can determine whether someone has folic acid deficiency.
Your doctor may perform a folic acid test if you’re showing symptoms of folic acid deficiency. They might also order the test if you’re experiencing symptoms of vitamin B-12 deficiency, as a lack of either vitamin can cause anemia.
The symptoms of a folic acid or vitamin B-12 deficiency include:
- diarrhea or constipation
- a swollen, red tongue
- bleeding gums
- a lack of appetite
- difficulty walking
- memory loss
The symptoms of anemia include:
- unusually pale skin
- rapid heart rate
- shortness of breath
If you already have either of these conditions, then a folic acid test can be done to see if the treatment is working. You may also need this test if you have an intestinal disorder, such as celiac disease or Crohn’s disease. These disorders make it difficult for your body to absorb folic acid properly, so you’ll need to be checked regularly.
A folic acid test is particularly important for women who are pregnant or who are planning to become pregnant. Consuming a sufficient amount of folic acid is critical for preventing certain birth defects and for ensuring the normal development of the fetus.
Before you take a folic acid test, notify your doctor about any supplements or medications you may be taking, as some can interfere with the results. Your doctor will probably tell you to avoid food and liquids for six to eight hours before the folic acid test. It’s usually preferable to fast all night and to have an early appointment the next morning.
A folic acid test involves taking a small sample of blood. The blood is typically drawn from a vein on the inside of the elbow. A healthcare provider will perform the test by doing the following:
- They’ll clean the area with an antiseptic.
- They’ll wrap an elastic band around your upper arm to slow down the flow of blood. This causes the veins below the band to swell.
- Once they find a vein, they’ll insert the needle and begin drawing blood.
- After they’ve collected the blood, they’ll remove the needle and apply a cotton ball to stop any bleeding.
- The puncture site will be covered with a bandage.
- The blood sample will then be sent to a laboratory for analysis.
Your doctor will schedule a follow-up appointment with you to go over the results.
The folic acid blood test poses no significant risks. You may get a small bruise at the puncture site, but you can lower the risk of bruising by keeping pressure on the site for a few minutes after the test. In rare cases, the vein may become swollen. This can be treated with a warm compress. Ongoing bleeding can also be a problem for people with bleeding disorders, so it’s important to tell your doctor if you have a bleeding disorder or if you take blood-thinning medications.
The normal reference range of folic acid in the blood is between 2.7 and 17.0 nanograms per milliliter.
Higher-than-normal folic acid levels usually aren’t problematic, but they may indicate a vitamin B-12 deficiency. Your body needs vitamin B-12 to use folic acid properly, so if vitamin B-12 levels are low, folic acid can’t be used. Your doctor may want to perform further testing to make sure elevated folic acid levels aren’t being caused by vitamin B-12 deficiency.
Lower-than-normal folic acid levels may indicate:
- folic acid deficiency
- malabsorption, or problems absorbing vitamins and minerals
Your doctor will explain what your specific results mean and what your next steps should be.