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Does this test have other names? 

Vitamin B9, folic acid test

What is this test?

This is a blood test to measure the concentration of folate in the liquid part of your blood, called serum, or in your red blood cells. The concentration in the red blood cells will be higher than in the serum.

Folate is a B vitamin naturally found in:

  • Leafy green vegetables, such as spinach, kale, collards, and romaine lettuce

  • Citrus fruits and juices

  • Dried beans, lentils, and peas

  • Yeast

  • Liver

  • Asparagus

  • Broccoli

  • Wheat germ

Many cereals, breads, and other grain products are fortified with folic acid, the synthetic version of folate.

Folate is needed to make red blood cells. It is also used to repair cells and to make DNA.

It also helps prevent cellular changes that may lead to cancer. Folate is also needed to help a baby's cells multiply during pregnancy. Low levels of folate during pregnancy can lead to brain or spine defects in the fetus. It can also lead to a type of anemia marked by fewer, but larger, red blood cells. 

Why do I need this test?

You may have this test to find out the cause of anemia, look at your nutritional status, or monitor a previous folate deficiency.

If you have anemia, you don't have enough red blood cells to carry oxygen to the cells in your body. A folate deficiency is just one cause of anemia. If you don't get enough folate or folic acid from food or vitamins, you may end up with a folate deficiency. Symptoms include:

  • Fatigue

  • Weakness

  • Pale skin, gums, eyes, and nails

  • Mouth ulcers and a red, sore tongue

  • Irritability

  • Shortness of breath

  • Weight loss

  • Numbness and tingling of fingers and toes

  • Forgetfulness

  • Confusion

  • Dizziness and fainting

  • Nausea, vomiting, diarrhea, although these are rare 

What other tests might I have along with this test?

Your doctor may also order a vitamin B12 test. Both folate and B12 are important to for healthy red blood cells. A deficiency in either B12 or folate can cause anemia.  

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

For blood plasma or serum, a normal result ranges from 2 to 10 nanograms per milliliter  (ng/mL) or 4 to 22 nanomoles per liter (nmol/L).

For red blood cells, a normal result ranges from 140 to 960 ng/mL or 550 to 2,200 nmol/L.

A test result that's lower than normal means you have a folate deficiency, and your doctor may recommend folic acid supplements. Once you begin taking supplements, the folate deficiency will go away within a few months. Your health care provider determines how much of a folic acid supplement you need based on your age and whether you are pregnant or breastfeeding.

Folate is water soluble, so any extra folate leaves your body in urine. But a buildup can sometimes happen during folic acid therapy. 

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore. 

What might affect my test results?

Many factors can contribute to a folate deficiency, including:

  • Poor nutrition

  • Being a vegetarian

  • Drinking too much alcohol

  • Advanced age

  • SmokingAnti-convulsion drugs

  • Chemotherapy

  • Pregnancy

  • Recent surgery

  • Nutrition absorption problems (Crohn's or celiac disease)

  • Kidney dialysis 

How do I get ready for this test?

You don't need to prepare for this test. Be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.