What Are the Dangers of High B12?

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Vitamin B12 is one of the eight B vitamins. Important for healthy nerve cell function, blood cell production, DNA and RNA synthesis, immune function and mood, vitamin B12 is essential to sustain a healthy body, according to the University of Maryland Medical Center. It is a water-soluble vitamin; therefore, it is not stored in the body and there are no adverse health effects from taking high levels of it.

B12 Functions

Vitamin B12 helps to produce S-adenosylmethionine, or SAMe, a substance that mediates immune function and mood. Vitamin B12 also helps to lower the amino acid homocysteine, which in high concentrations is associated with coronary artery disease. B12 converts carbohydrates to glucose, or sugar, used to produce energy and helps the body to metabolize fats, proteins and carbohydrates to produce energy, notes the University of Maryland Medical Center

B12 Deficiency

While having too much Vitamin B12 is not a problem, vitamin B12 deficiency causes pernicious anemia. Mild pernicious anemia can occur in response to a poor diet or low stomach acid. Stomach acid is needed to absorb vitamin B12 from food. The signs and symptoms of a B12 deficiency include fatigue, weakness, pale skin, diarrhea, shortness of breath, weight loss, numbness, anxiety and tingling in the fingers or toes, confusion, imbalance, mood swings and memory loss. Severe pernicious anemia causes neurological damage. Those at risk of developing a B12 deficiency are vegans, since they do not eat dairy, eggs or meat products – foods that contain B12; people who have a helicobacter pylori infection, which damages the acid secreting cells in the stomach; individuals with malabsorption problems, eating disorders, HIV or the elderly, according to the University of Maryland Medical Center.

B12 Dangers

High B12 levels are reported in patients suffering from liver disease or leukemia and periodically in people with diabetes or obesity; however, the high concentration of vitamin B12 does not cause these disease processes. There are no adverse affects from taking high doses vitamin B12. Vitamin B12 is a water-soluble substance; therefore, the body will take what it needs and excrete the rest in the urine, according to the University of Michigan Health System and Guillermo Arroyave Ph.D.

B12 Sources

Vitamin B12 is found in animal dietary sources such as shellfish, fish, organ meats--especially liver and kidneys--dairy, eggs, pork and beef. Vitamin B12 can also be taken as a supplement orally or as an injection, according to the University of Maryland Medical Center.


Vitamin B12 may conflict with certain medications such as anticonvulsants, colchicine to treat gout, medications to lower cholesterol, H2 blockers, some diabetes medications, medications to reduce stomach acid, chemotherapy drugs and antibiotics such as tetracycline. Consult your physician before taking vitamin B12 when you are prescribed medication, according to the University of Maryland Medical Center.