A vitamin B12 level test checks the amount of vitamin B12 in the body. Normal levels usually range from 200 to 900 picograms per milliliter, but the way of measuring will depend on the laboratory.

Vitamin B12 is necessary for several bodily processes, including nerve function and the production of DNA and red blood cells.

A person whose vitamin B12 levels are outside of the normal range will require treatment. High B12 levels may indicate liver disease, diabetes, or certain types of leukemia. Low levels of the vitamin may indicate a B12 deficiency or pernicious anemia.

Read on to learn more about testing B12 levels and what the test results mean.

The vitamin B12 level test checks how much vitamin B12 is in the body. The results can help doctors to determine if abnormal vitamin B12 levels are causing symptoms.

A doctor may order a vitamin B12 level test if a person has any of the following:

Suspected vitamin B12 deficiency

According to researchers, in the USA, approximately 6% of adults younger than 60 have vitamin B12 deficiency. That rate jumps to 20% in people ages 60 and over. Signs and symptoms of deficiency include:

Infants with vitamin B12 deficiency may fail to thrive. They may experience movement problems in addition to delayed development. If left untreated, it can lead to brain damage.

Pernicious anemia

People with symptoms of pernicious anemia may also need a vitamin B12 level test. Pernicious anemia, which causes low levels of red blood cells, results from an inability to absorb vitamin B12.

It often affects older adults or those who lack intrinsic factor. Intrinsic factor is a substance in the stomach that binds to vitamin B12 so that the body can absorb it.

Symptoms of pernicious anemia include:

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 B12 deficiency and make its neurological symptoms worse.

They can also increase the likelihood of anemia.

Symptoms of other conditions

An abnormally high vitamin B12 status can be an early sign of:

A doctor may use the results of a vitamin B12 test to help form their diagnosis.

Doctors usually use a blood test to check vitamin B12 status, but home urine tests are also available. A doctor can check vitamin B12 as part of a standard blood test.

Although it is not necessary to fast before a B12 test, a person may need to if the doctor is also using the test to look at other components in the blood.

It is important that individuals tell their doctor about any medications and supplements they are taking, as some can affect the results.

Certain people are more at risk of vitamin B12 deficiency than others, especially those who have low stomach acid or other digestive issues. Stomach acid separates vitamin B12 from food so that the body can absorb it more efficiently.

The following groups of peopleare more likely than others to experience low vitamin B12 levels:

The results may be:

  • High. An abnormally high vitamin B12 status is anything over 900 pg/mL. This result may suggest liver or kidney problems, diabetes, or certain forms of leukemia.
  • Low. Levels of vitamin B12 are low if they are below 200 pg/mL. This result suggests a vitamin B12 deficiency, pernicious anemia, or an overactive thyroid. People with low vitamin B12 levels often experience neurological symptoms.

The result ranges vary from one laboratory to another, so it is important to discuss the results and their meaning with a doctor.

The doctor may also check the levels of methylmalonic acid (MMA) and other substances to evaluate for vitamin B12 deficiency. These lab values help detect a vitamin B12 deficiency during the early stages.

There is no upper limit for vitamin B12 intake because consuming high levels does not cause problems. However, having naturally high levels of vitamin B12 in the body may be a cause for concern, as it suggests a severe underlying condition. Doctors will aim to treat the underlying medical condition, rather than the elevated levels of vitamin B12.

Individuals with low vitamin B12 levels often require regular injections of the vitamin. These shots are more effective than supplements at raising vitamin B12 levels, especially when people have medical conditions that may make it more difficult to absorb supplements.

For some people, high doses of vitamin B12 supplements may improve B12 status.

Although absorption difficulties and other medical issues often cause low vitamin B12 levels, some people may be deficient because they do not get enough vitamin B12 from their diet. This is especially true for vegans and vegetarians.

Foods rich in vitamin B12 include:

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 B12, older adults should aim to meet their vitamin B12 needs through fortified foods and vitamin supplements.

Recommended dietary allowances of vitamin B12

Adults and adolescents over 14 years of age require 2.4 micrograms (mcg) of vitamin B12 daily. This increases to 2.6 mcg during pregnancy and 2.8 mcg when breast-feeding.

Below are some commonly asked questions about high B12 levels.

What does it mean if your B12 is high?

Naturally high levels of vitamin B12 may be an early sign of a serious, even life-threatening, disease. It can point to:

  • liver disease
  • diabetes
  • certain types of leukemia

What should I do if my B12 level is high?

A person with high B12 levels should consult a doctor as it can indicate a serious underlying condition, such as liver dysfunction or leukemia.

Vitamin B12 is an essential nutrient that plays a vital role in overall health. A vitamin B12 level test determines a person’s vitamin B12 status. A doctor may recommend this test to people who have symptoms of a deficiency or who have a higher risk of low vitamin B12 in the body.

People can avoid vitamin B12 deficiency by eating a balanced diet and including several sources of vitamin B12 daily or taking supplements. If they have issues absorbing vitamin B12 from food sources, oral supplements or injections of the vitamin can help prevent symptoms and complications.