Vitamin B12 Test Fact Sheet

Vitamin B12 (cobalamin) is an important nutrient in many foods such as meat and dairy products, as well as added to others such as breakfast cereals. Yet, between 5 to 20 percent of adults will become deficient at some point in their lives. The absorption of vitamin B12 is more complex than with some nutrients. Not only does is require a well-functioning digestive system and healthy saliva to break down and absorb the nutrient, it also requires a healthy liver to store it.

Vitamin B12 is necessary for many body processes. Without sufficient vitamin B12, people may feel tired, depressed or experience a decline in cognitive function. Low vitamin B12 levels may also make someone more susceptible to cancer.

Aging populations and vegetarians specifically need to watch their vitamin B12 levels. Normal levels of B12 are necessary for a range of body processes, such as to synthesize DNA. Having too little B12 is not always obvious at first, but if not corrected within a year of becoming deficient, it can cause permanent damage. Supplementing with vitamin B12 can typically reverse damage before a year has gone by, or slow decline that occurs after a year. Identifying the problem requires a blood test to measure B12. The test is simple and could be the key to preventing serious issues.

Overview of the Test

A vitamin B12 test is critical for detection of a deficiency. Catching a deficiency early allows for fast treatment that may prevent neurologic damage. Too little vitamin B12 may lead to nerve damage, and in extreme cases could cause mental confusion or dementia.

Although the body stores vitamin B12, people can become deficient in a short time. Some people with malabsorption issues could become deficient in a matter of months. Even people who eat a diet high in vitamin B12 could still have low levels if their body is not absorbing what they eat. A vitamin B12 test will tell someone almost immediately if they are at risk.

A blood test that reveals low levels of vitamin B12 could indicate:

  • A lack of B12 in the diet
  • Digestive disorders
  • A lack of a protein called intrinsic factor
  • Elevated heat production

Pregnant women may also be at risk of low levels of vitamin B12.

A vitamin B12 test could also indicate that someone has too much vitamin B12, though this is unusual. Liver disease or myeloproliferative disorders may cause elevated levels of vitamin B12.

How is it done?

A vitamin B12 is a simple blood test that examines a sample taken by a health care worker for levels of the vitamin in the blood. A healthy level of vitamin B12 is between 200 and 900 picograms per milliliter (pg/mL).

Who does it?


When and How Often?

As people age, their digestive function often declines. The ability to digest and optimally absorb food may decrease after age 50. Some experts therefore suggest that people age 50 and over begin to supplement with around 2.4 micrograms of B12 daily. A yearly vitamin B12 test can establish that people’s levels are in a healthy range and likely catch any problem before it does permanent damage.

Experiencing symptoms of a deficiency also indicate the need for a B12 test. Fatigue, depression and symptoms of a nervous system problem warrant testing. Feeling weak, experiencing poor balance and having a sensation of tingling in the extremities are signs of possible nervous system issues.

Doctors may also order vitamin B12 tests if they suspect certain conditions, including megaloblastic anemia, delirium and dementia.


A vitamin B12 test is affordable. The test may cost around $40 to $50 if not covered by insurance.


Having one’s blood taken is very safe. Some people experience mild to moderate pain. After blood is drawn, some people may feel a throbbing sensation that should go away.


Last reviewed 26/Feb/2014


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Whilst wielding a couple of dumbbells in a gym class in 2003, Kate experienced an epiphany around the lack of accepted best practice guidelines when it came to staying well and avoiding disease. Kate realized that she had no chance of slowing her own aging process unless she became better educated about her options.

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