Vitamin B12 is a water-soluble vitamin necessary for red blood cell formation, DNA synthesis, metabolism and central nervous system function. Vitamin B12 is found naturally in certain foods, added to fortified foods and found in dietary supplements and prescription medications. It is important to maintain adequate levels of B12 to avoid deficiencies and other complications. Vitamin B12 status is accessed via serum or plasma B12 levels.
The Test
A vitamin B12 test is done by drawing blood from a vein in your arm or hand. For infants and young children, a sharp tool, or lancet, is used to puncture the skin and make it bleed. The blood is then collected, put into a small tube and sent to the lab for assessment. You should not eat or drink for at least eight hours prior to a vitamin B12 test.
How Is It Used?
A vitamin B12 level is typically drawn to diagnose or monitor conditions related to a deficiency such as pernicious or megaloblastic anemia, certain nervous system symptoms including numbness or tingling in the arms and legs, weakness and loss of balance or signs of dementia and delirium. Certain people, particularly older adults, anemia patients, vegetarians, those with reduced levels of stomach acid or intestinal disorders and those who have difficulty absorbing B12 from food are at a higher risk of developing vitamin B12 deficiency.
Normal Levels
Normal vitamin B12 values are 200 to 900 picograms per milliliter. Talk with your physician about what your results mean, as normal values may vary slightly from laboratory to laboratory.
Increased Levels
Increased vitamin B12 levels are uncommon. Most children and adults in the United States consume the recommended amount of vitamin B12, according to the Office of Dietary Supplements. In addition, no upper limits have been established for vitamin B12, meaning that higher doses of vitamin B12 are harmless. Some health conditions, however, can increase vitamin B12 levels. These include liver disease such as cirrhosis or hepatitis, leukemia and polycythemia.
Decreased Levels
Levels less than 200 picograms per milliliter suggest you have a vitamin B12 deficiency. Older adults are at an increased risk of deficiency, due to inadequate intake and impaired absorption. Therefore they may experience a deficiency with levels of 200 to 500 picograms per milliliter. Causes of a deficiency include insufficient vitamin B12 in the diet, conditions such as celiac disease or Crohn's disease, which cause malabsorption, a lack of intrinsic factor, above normal heat production and pregnancy.
Factors Affecting B12 Levels
Variables can affect your vitamin B12 levels. For example, excessive bleeding, fainting or feeling light-headed, blood accumulation under the skin, infection and rupture of red blood cells can alter your B12 values. Folate is closely associated with vitamin B12 and if taken as a supplement it can mask the symptoms of B12 deficiency.
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