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 to diagnose or monitor certain health problems.
Your doctor might order a vitamin B12 test if you show symptoms of anemia or issues with the nervous system like mental changes, weakness, loss of balance or numbness, pain, and tingling in the arms and legs. A vitamin B12 test can also be ordered as a follow-up if you had an abnormal blood test that suggests megaloblastic anemia, when red blood cells are unusually large and do not function properly.
What does the test measure?
The test measures your vitamin B12 levels, which are important for many aspects of 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 in all of our cells.
When should I get this test?
Up to 15% of people in the U.S. have a vitamin B12 deficiency. 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 vitamin B12 deficiency due to age or preexisting health conditions. They may undergo regular vitamin B12 testing to check whether their levels are normal.
Anemia is one factor related to inadequate vitamin B12, with symptoms including fatigue, difficulty concentrating, pale skin, shortness of breath, diarrhea, nausea, and loss of appetite. With anemia, your body doesn’t have enough healthy red blood cells to carry oxygen to tissues.
A vitamin B12 deficiency can lead to a type of anemia known as megaloblastic anemia. Megaloblasts may be detected through routine blood testing before you develop symptoms of anemia. When this happens, follow-up testing is typically performed, including a vitamin B12 test.
Nervous system symptoms are another trigger for vitamin B12 testing. Common symptoms include neuropathy, weakness, poor balance, confusion, and dementia.
And you might have risk factors associated with a vitamin B12 deficiency, including age (75 years or older), lack of protein in the diet, medications that interfere with vitamin B12 absorption like histamine blockers, or decreased absorption of vitamin B12 because of a stomach disease like celiac, cancer, or pancreatic insufficiency.
People more likely to experience low vitamin B12 levels include older adults, children, vegans and vegetarians, diabetics, those who have had gastric bypass surgery, women who are breastfeeding, and if you have a condition that can impact absorption like Crohn’s disease.
Your doctor can best assess the nuances involved in determining whether you should get vitamin B12 testing because many of these symptoms overlap with other health conditions and could require different types of screening.
