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Ingredient Type: Vitamin

Also Known As: Methylcobalamin, Cobalamin, B12

Vitamin B-12 is one of eight B vitamins and an essential nutrient for all animals obtained only through the diet. It is found in meat & seafood, eggs, and milk. Vitamin B-12 plays a key role in the normal functioning of the brain and nervous system, as well as in the formation of red blood cells. It is involved in the metabolism of every cell of the human body, especially affecting DNA synthesis, fatty acid, and amino acid metabolism.

Methylcobalamin is a cobalamin, a form of vitamin B12.  It is equivalent physiologically to Vitamin B12, It is the most functional B12 supplement because it is already in bioavailable form,  the body does not need to convert it.  Methylcobalamin is the only form of B12 that can cross the blood-brain barrier without assistance or conversion and it is the only form that acts on the nervous system. (14, 15).

Vitamin B12 is an essential water-soluble vitamin that is commonly found in a variety of foods, such as fish, shellfish, meat, eggs, and dairy products. It is frequently used in combination with other B vitamins in vitamin B complex formulations.

The risk for vitamin B12 deficiency is higher with increased age, male gender, and in people of Caucasian and Latin American descent. Deficiency in vitamin B12 results from the insufficient intake, malabsorption from food, and other medical conditions (9). However, body stores of vitamin B12 are large, and it is widely available in food. Vitamin B12 deficiency is almost always caused by a disorder of absorption (10).

When used for vitamin B12 deficiency can include neuropsychiatric disorders such as depression (3), paresthesias, ataxia, memory loss, weakness, and personality and mood changes without anemia (4). Some neurologic symptoms and elevated homocysteine levels can occur without any signs of B12 deficiency anemia (5). Vitamin B12 deficiency is associated with impaired cognitive performance in adolescents (aged 10-16 years) who have been fed a strict vegetarian diet from infancy to 6 years of age. Consequences of low vitamin B12 intake during childhood and its effect on cognitive functioning in adulthood are unknown (6). Elevated methylmalonate or methylmalonic acid (MMA) levels occur early in vitamin B12 deficiency and may precede other symptoms (7). In combination with homocysteine levels, MMA levels can be used to diagnose vitamin B12 deficiency (8).


Vitamin B-12 is used in health supplements today to support the formation of healthy red blood cells, energy production, and mental health. It also works along with the whole B-Complex family of nutrients to promote overall good health.

improved concentration and improving cognition, mood elevation and boosting energy.


Some research shows that elevated serum homocysteine and low folate and vitamin B12 levels may be associated with a poor cognitive function, cognitive decline, and dementia (12).

Vitamin B12 deficiency can take months to years to become symptomatic due to large body stores. Normal serum vitamin B12 levels range between 200-900 pg/mL. Serum concentrations less than 200 pg/mL indicate deficiency, and concentrations less than 100 pg/mL usually result in megaloblastic anemia or neurologic damage (1). Vitamin B12 deficiency results in megaloblastic anemia, gastrointestinal lesions, and neurologic damage, beginning with an inability to produce myelin and progressing to degeneration of the axon and nerve head (2). Neurologic symptoms caused by vitamin B12 deficiency can include neuropsychiatric disorders such as depression (5,6), paresthesias, ataxia, memory loss, weakness, and personality and mood changes without anemia. (3)

Vitamin B12 deficiency is especially common in older adults, primarily due to lack of intrinsic factor and malabsorption (2). Vitamin B12 in foods such as milk and fortified bread is approximately 55% to 60% absorbed by people over 60 years of age (4).

Other people at risk for vitamin B12 deficiency include strict vegetarians and people with increased vitamin B12 requirements associated with pregnancy, thyrotoxicosis, hemolytic anemia, hemorrhage, malignancy, and hepatic and renal disease. Moderate consumption of animal products may not be sufficient to restore and maintain vitamin B12 levels in adolescents aged 9-15 years who have eaten a strict vegetarian diet with an inadequate intake of vitamin B12 from infancy to six years of age. A higher dietary intake of vitamin B12 or supplements is usually needed in order to restore and maintain optimal vitamin B12 levels in these adolescents (4).


Considered safe when used orally in appropriate amounts. Vitamin B12 is generally considered safe, even in large doses.


  1. Watanabe, F. Vitamin B12 sources, and bioavailability. Exp.Biol.Med.(Maywood.) 2007;232(10):1266-1274.
  2. Okuda, K. Discovery of vitamin B12 in the liver and its absorption factor in the stomach: a historical review. J.Gastroenterol.Hepatol. 1999;14(4):301-308
  3. Ortiz-Hidalgo, C. [George H. Whipple. Nobel Prize in Physiology or Medicine in 1934. Whipple’s disease, pernicious anemia, and other contributions to medicine]. Gac.Med Mex. 2002;138(4):371-376.
  4. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  5. Kaltenbach, G., Noblet-Dick, M., Andres, E., Barnier-Figue, G., Noel, E., and Vogel, T. Reponse precoce au traitement oral par vitamine B12 chez des sujets ages hypovitaminiques. Annales de Medecine Interne (Paris) 2003;154:91-95.
  6. Xu G, Lv ZW, Feng Y, et al. A single-center randomized controlled trial of local methylcobalamin injection for subacute herpetic neuralgia. Pain Med 2013;14(6):884-94
  7. Meta-analysis of methylcobalamin alone and in combination with lipoic acid in patients with diabetic peripheral neuropathy. Diabetes Res Clin Pract 2013;101(2):99-105
  8. Xu G, Lv ZW, Xu GX, Tang WZ. Thiamine, cobalamin, locally injected alone or combination for herpetic itching: a single-center randomized controlled trial. Clin J Pain 2014;30(3):269-78.
  9. Stracke, H., Lindemann, A., and Federlin, K. A benfotiamine-vitamin B combination in the treatment of diabetic polyneuropathy. Exp Clin Endocrinol.Diabetes 1996;104(4):311-316.
  10. Simeonov, S., Pavlova, M., Mitkov, M., Mincheva, L., and Troev, D. Therapeutic efficacy of “Milgamma” in patients with painful diabetic neuropathy. Folia Med (Plovdiv.) 1997;39(4):5-10.
  11. Fonseca VA, Lavery LA, Thethi TK, et al. Metanx in type 2 diabetes with peripheral neuropathy: A randomized trial. Am J Med 2013;126(2):141-9.
  12. Li, G. [Effect of mecobalamin on diabetic neuropathies. Beijing Methycobal Clinical Trial Collaborative Group]. Zhonghua Nei Ke.Za Zhi. 1999;38(1):14-17
  13.  Lauritzen CH, Reuter HD, Repges R, Bohnert K, and Schmidt U. Treatment of premenstrual tension syndrome with Vitex agnus castus. controlled, double-blind study versus pyridoxine. Phytomed 1997;4(3):183-189
  14. Kikuchi M, Kashii S, Honda Y, et al. Protective effects of methylcobalamin, a vitamin B12 analog, against glutamate-induced neurotoxicity in retinal cell culture. Invest Ophthalmol Vis Sci. 1997 Apr;38(5): 848-54.
  15. Izumi Y1, Kaji R. Vitamin B12 metabolism and massive-dose methyl vitamin B12 therapy in Japanese patients with multiple sclerosis. Intern Med. 1994 Feb;33(2):82-6.

See the National Institutes of Health Office of Dietary Supplements entry for vitamin B12, this American Academy of Family Physicians article on vitamin B12, the Mayo Clinic entry for vitamin B12, the entry for vitamin B12, or the WebMD entry for vitamin B12 for more information.