This page helps you to understand blood test results for Vitamin B12 and gives you the reference range to determine if your lab test results mean that you have high, low or normal Vitamin B12 levels.
We outline the risk factors associated with both raised and lower Vitamin B12 levels.
Reference Ranges for Vitamin B12:
|US Conventional Units||pg/ml or ng/L||400-914||150-300||<150 or> 914|
|Standard International Units||pmol/L||295-675||111-294||<111 or > 675|
What is Vitamin B12
Vitamin B12 is a nutrient found naturally in a wide variety of animal foods and is added to some fortified foods. Plant foods have no vitamin B12 unless they are fortified. Two steps are required for the body to absorb vitamin B12 from food. First, hydrochloric acid in the stomach separates vitamin B12 from the protein to which vitamin B12 is attached in food. After this, vitamin B12 combines with a protein made by the stomach called intrinsic factor and is absorbed by the body .
Function of Vitamin B12
All B vitamins help the body convert food into fuel (glucose), which is used to produce energy. These B vitamins also help the body use fats and protein, and are needed for healthy skin, hair, eyes, and liver. They also help the nervous system function properly .
Vitamin B12 is an especially important vitamin for maintaining healthy nerve cells, and it helps in the production of DNA and RNA, the body’s genetic material. In the methylation cycle vitamin B12 works closely with vitamin B9, also called folate or folic acid, to help make red blood cells and to help iron work better in the body. Folate and B12 work together to produce S-adenosylmethionine (SAMe), a compound involved in immune function and mood .
Vitamins B12, B6, and B9 work together to control blood levels of the amino acid homocysteine. High levels of homocysteine are associated with heart disease.
Risk factors associated with Vitamin B12
Cardiovascular disease – An elevated homocysteine level has been associated with an increased risk of cardiovascular disease. B12 along with B9 and B9 are involved in homocysteine metabolism and researchers have hypothesized that they reduce cardiovascular disease risk by lowering homocysteine levels. However, researchers do not know whether high homocysteine levels actually cause heart disease or if it is merely a marker for it .
Fatigue – Fatigue is one of the most widely reported symptoms of a vitamin B12 deficiency. Studies suggest that people with chronic fatigue syndrome might benefit from B12 injections 
Pernicious anemia – Pernicious anemia is a type of anemia that happens when stomach cells are not able to make intrinsic factor. Without intrinsic factor, your body cannot absorb vitamin B12 .
Notable variations by demographic group
- Vitamin B12 tends to be lower in elderly people. This may be because their diets are not as healthy, or because they have less stomach acid, which the body needs to absorb B12 .
- B12 also tends to be lower in Vegans and vegetarians who do not eat dairy or eggs, since vitamin B12 is found only in animal products .
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Diet to improve Vitamin B12
Vitamin B12 is found naturally in a wide variety of animal foods and is added to some fortified foods. Plant foods have no vitamin B12 unless they are fortified. You can get recommended amounts of vitamin B12 by eating a variety of foods including the following:
- Fish, meat, poultry, eggs, milk, and other dairy products.
- Beef liver and clams are particularly high in B12
- Some food products are fortified with vitamin B12 .
Supplements for Vitamin B12
Vitamin B12 is found in almost all multivitamins. Dietary supplements that contain only vitamin B12, or vitamin B12 with nutrients such as folate and other B vitamins, are also available.
Vitamin B12 is also available in sublingual forms (which are dissolved under the tongue). There is no evidence that sublingual forms are better absorbed than pills that are swallowed.
A prescription form of vitamin B12 can be administered as a shot. This is usually used to treat vitamin B12 deficiency .
Vitamin B12 supplements are available in a number of forms including methylcobalamin, adeonsylcobalamin, hydroxycobalamin and cyanocobalamin which is considered inferior to the other forms listed here .
Exercise to improve Vitamin B12
The B-vitamins are necessary in the energy-producing pathways of the body, and for the repair of damaged cells. Individuals with poor or marginal nutritional status for a B-vitamin may have decreased ability to perform exercise at high intensities, and should correct deficiencies before participating in intense training.
Sleep for Vitamin B12
Giving vitamin B12 with bright light therapy may be helpful for people with circadian rhythm sleep disorders . More research is needed in this area.