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Vitamin B-12 and Folate

Does this test have other names?

Cobalamin, Cbl, folic acid, FA, B12

What is this test?

This test measures the levels of vitamin B-12 (or B12) and folate in your blood.

Your body needs vitamin B-12, also called cobalamin, and folate, also called folic acid, to function normally. Both nutrients play important roles in creating red blood cells and making DNA and RNA to help build cells. B-12 also helps your nervous system function as it should.

B-12 is found in fortified cereals and animal products like fish, meat, eggs, and dairy. It's also in dietary supplements, as cyanocobalamin.  Folate is found naturally in green leafy vegetables, fruits, and beans. It's also added to enriched cereals and grains.

People who have pernicious anemia may have low B-12 levels because this condition prevents them from absorbing B-12. A low folate level can also be the result of a poor diet or alcohol abuse.

Why do I need this test?

You may need this test if you are taking medicines that could interfere with how your body absorbs B-12 or folate. You may also have this test if you have a disease or condition that could lead to B-12 deficiency. Symptoms of B-12 deficiency include:

  • Fatigue

  • Headaches

  • Numbness or "pins and needles" in the hands and feet

  • Difficulty walking

  • Memory loss

  • Difficulty thinking normally

  • Changes in mood

Symptoms of having too little folate are diarrhea, weight loss, and other vague symptoms that could be caused by many other conditions.

It's important that women who are pregnant, thinking of becoming pregnant, or breastfeeding have enough folate.

This test measures both vitamin B-12 and folate, but either of these nutrients can be measured separately in different lab tests. Your healthcare provider may order this combined test if you have a condition for which it's important to know both levels.

What other tests might I have along with this test?

Your healthcare provider may also order these tests:

  • Homocysteine and methylmalonate, or methylmalonic acid. These substances can build up in your body if you have a B-12 or folate deficiency.

  • Red blood cell

  • Pernicious anemia. This includes measuring levels of gastrin, pepsinogen I, pepsinogen II, and antibodies against a substance called intrinsic factor.

What do my test results mean?

Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you. 

Results are given in nanograms per milliliter (ng/mL). A normal range for vitamin B-12 is 200 to 900 ng/mL.

If your B-12 results are low, it may mean you have:

  • Pernicious anemia

  • Stomach issues, such as lack of stomach acid, that make it difficult to absorb the vitamin

  • Folate deficiency

Your diet can also lead to B-12 deficiency. Some vegetarians or vegans who don't eat eggs or other dairy products may develop this deficiency.

Your B-12 results may also be higher or lower if you have had recent nuclear medicine studies using radiation. They can mean that you have:

  • Severe liver disease

  • Chronic granulocytic leukemia

If the test is done on your blood plasma, a normal range for folate is 2 to 10 ng/mL. If the test is done on red blood cells, a normal range is 140 to 960 ng/mL.

If your folate results are low, it may mean you have:

  • A diet that doesn't provide enough folate

  • Difficulty absorbing the nutrient

  • Alcohol abuse

  • B-12 deficiency

  • Hemolytic anemia

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. 

What might affect my test results?

Being pregnant can affect your results, as can eating foods that are high or low in folate. Alcohol use can also affect your results. Certain medicines can also affect your results. These include:

  • Birth control pills

  • Methotrexate

  • Trimethoprim

  • Phenytoin

  • Azulfidine

How do I get ready for this test?

Tell your healthcare provider about health conditions you have, and how much alcohol you drink regularly. Be sure your healthcare provider 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.

Online Medical Reviewer: Freeborn, Donna, PhD, CNM, FNP
Online Medical Reviewer: Haldeman-Englert, Chad, MD
Date Last Reviewed: 12/1/2017
© 2000-2021 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.