Vitamin B12 testing measures the level of vitamin B12 in your blood. Having a vitamin B12 deficiency, or a low level of this essential vitamin, can cause a range of health issues, including anemia and nervous system problems.
Vitamin B12 levels may be low for a number of reasons, including inadequate dietary intake, the use of certain medications, advanced age, or conditions that make it harder for the body to absorb vitamin B12 from your food.
Testing for vitamin B12 requires a sample of blood. Measuring your vitamin B12 level helps your health care provider to diagnose a possible deficiency and recommend appropriate treatment, if needed.
The purpose of vitamin B12 testing is to determine whether you have a deficiency or a lower-than-normal level of B12 in your body. Sometimes a vitamin B12 level will be tested by itself and other times it will be measured along with other tests for the purposes of diagnosing or monitoring certain health problems.
Diagnosis
Vitamin B12 testing may be ordered to determine the cause of a patient’s symptoms. It may also be ordered after an abnormal result on a different blood test to learn more about an individual’s health. Diagnostic purposes for vitamin B12 testing include:
Monitoring
Vitamin B12 testing may also be used for monitoring a patient’s health over time. Checking blood levels of vitamin B12 may be done:
Screening
Screening is testing that is performed before there are visible symptoms of a health problem, like a vitamin B12 deficiency. At this time, there are no guidelines regarding screening of asymptomatic people for vitamin B12 deficiency.
However, doctors may choose to check vitamin B12 levels in people with certain risk factors that put them at a higher risk of a deficiency, such as the elderly or people who follow a vegan diet, which does not include any foods from animal sources.
Vitamin B12 is a nutrient that is important for many aspects of human health. Adequate levels of vitamin B12 are needed for your body to maintain a healthy nervous system, make red blood cells, and create DNA, the genetic material present in all of our cells.
Vitamin B12 occurs naturally in animal proteins, such as red meat, fish, poultry, eggs, and dairy. Other foods, like breakfast cereals, nutritional yeast, and some plant milks, may be fortified with vitamin B12. This vitamin is also available as a supplement and as a prescription medication.
In food, vitamin B12 is bound to protein. In order for your body to absorb it, the vitamin must be released from the protein. As your body digests food, enzymes in your digestive tract separate vitamin B12 from these proteins. The freed vitamin B12 then combines with a protein made by your body called intrinsic factor, which is secreted by cells in the stomach. Together, vitamin B12 and intrinsic factor are absorbed in the lower end of the small intestine.
Vitamin B12 testing is usually performed when you have symptoms of a vitamin B12 deficiency, such as anemia or nervous system problems. Some people are at a greater risk of having a vitamin B12 deficiency due to their age or preexisting health conditions and may undergo regular vitamin B12 testing to check whether their B12 levels are normal.
The following information describes several circumstances in which vitamin B12 testing may be recommended by a doctor.
Anemia
Anemia is a condition in which your body does not have enough healthy red blood cells. Red blood cells carry oxygen to your body tissues. When you don’t have enough healthy, properly functioning red blood cells, you may have symptoms like:
A vitamin B12 deficiency can lead to a type of anemia known as megaloblastic anemia. In megaloblastic anemia, the red blood cells are large, underdeveloped, and abnormally shaped. These abnormal red blood cells, called megaloblasts, do not function normally.
Megaloblasts may be detected through routine blood testing before a person develops symptoms of anemia. When this happens, follow-up testing is typically performed, including a vitamin B12 test.
Nervous system symptoms
Your health care provider may recommend a vitamin B12 test to determine if a low level of vitamin B12 is causing nervous system symptoms. These symptoms may include:
Risk factors
Certain factors make an individual more likely to have a vitamin B12 deficiency. Your doctor may order vitamin B12 testing for you if you have one or more of the following risk factors:
