Vitamin B-12 level test: Uses, normal ranges, and results

Vitamin B-12 is necessary for several bodily processes, including nerve function and the production of DNA and red blood cells.

A person whose vitamin B-12 levels are outside of the normal range will require treatment. Low levels of the vitamin can cause neurological symptoms, as well as fatigue, constipation, and weight loss. High B-12 levels may indicate liver disease, diabetes, or another condition.

Read on to learn more about testing B-12 levels and what the test results mean.

Why is a vitamin B-12 level test useful?

The vitamin B-12 level test checks how much vitamin B-12 is in the body. The results can help doctors to determine if abnormal vitamin B-12 levels are causing symptoms.

A doctor may order a vitamin B-12 level test if a person has any of the following:

Suspected vitamin B-12 deficiency

Researchers believe that up to 15 percent of people in the United States have vitamin B-12 deficiency. Signs and symptoms of deficiency include:

  • confusion
  • dementia
  • depression
  • difficulty maintaining balance
  • fast heartbeat
  • numbness and tingling in the hands and feet
  • poor memory
  • a sore mouth or tongue

Infants with vitamin B-12 deficiency may fail to thrive. They may experience movement problems in addition to delayed development.

Pernicious anemia

People with symptoms of pernicious anemia may also need a vitamin B-12 level test. Pernicious anemia, which causes low levels of red blood cells, results from an inability to absorb vitamin B-12.

It often affects older adults or those who are lacking intrinsic factor. Intrinsic factor is a substance in the stomach that binds to vitamin B-12 so that the body can absorb it.

Symptoms of pernicious anemia include:

  • constipation
  • fatigue
  • loss of appetite
  • pale skin
  • weakness
  • weight loss

High serum folate levels

Serum folate is the level of folic acid in the blood. High serum folate levels can mask the symptoms of vitamin B-12 deficiency and make its neurological symptoms worse.

They can also increase the likelihood of anemia.

Symptoms of other conditions

An abnormally high vitamin B-12 status can be an early sign of liver disease, diabetes, or certain types of leukemia. A doctor may use the results of a vitamin B-12 test to help form their diagnosis.

Risk factors for low vitamin B-12 levels

Certain people are more at risk of vitamin B-12 deficiency than others, especially those who have low stomach acid or other digestive issues. Stomach acid separates vitamin B-12 from food so that the body can absorb it more efficiently.

The following groups of people are more likely than others to experience low vitamin B-12 levels:

  • older adults
  • children
  • vegans and vegetarians
  • people with diabetes
  • people with conditions that reduce vitamin B-12 absorption, including celiac disease and Crohn’s disease
  • people who have had gastric bypass surgery
  • those who are breast-feeding
  • people who are taking medicines such as chloramphenicol, proton pump inhibitors, or H2 blockers

Although absorption difficulties and other medical issues often cause low vitamin B-12 levels, some people may be deficient because they do not get enough vitamin B-12 from their diet. This is especially true for vegans and long-term vegetarians.

Foods rich in vitamin B-12 include:

  • fish and seafood
  • meat
  • eggs
  • dairy products
  • fortified plant-based dairy alternatives
  • fortified breakfast cereals
  • fortified nutritional yeast

Vitamin supplements can make up for a shortfall in the diet, especially for vegans and strict vegetarians. As it can be easier for their body to absorb supplements than naturally occurring vitamin B-12, older adults should aim to meet their vitamin B-12 needs through fortified foods and vitamin supplements.

Recommended dietary allowances of vitamin B-12

Adults and adolescents over 14 years of age require 2.4 micrograms (mcg) of vitamin B-12 daily. This increases to 2.6 mcg during pregnancy, and 2.8 mcg when breast-feeding.


Vitamin B-12 is an essential nutrient that plays a vital role in overall health. A vitamin B-12 level test determines a person’s vitamin B-12 status. A doctor may recommend this test to people who have symptoms of a deficiency or who have a higher risk of low vitamin B-12 in the body.

People can avoid vitamin B-12 deficiency by eating a balanced diet and including several sources of vitamin B-12 daily or taking supplements. If they have issues absorbing vitamin B-12 from food sources, oral supplements or injections of the vitamin can help to prevent symptoms and complications.

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