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Vitamin B12
What is it? Overview Usage Side Effects and Warnings

Vitamin B12 Usage

Written by FoundHealth.


Effect of Vitamin B12 on Carpal Tunnel Syndrome

Read more about Carpal Tunnel Syndrome and Vitamin B12.

Therapeutic Uses

It appears that individuals who take medications that dramatically lower stomach acid, such as H2 blockers or proton pump inhibitors , would benefit by taking B 12 supplements. 1 2 3 4 5 Other individuals likely to be deficient in B 12 , such as the elderly, or those taking the medications listed in Requirements/Sources, might well benefit from a daily B 12 supplement to prevent B 12 deficiency.

For pernicious anemia, B 12 injections are traditionally used but research has shown that oral B 12 works just as well, provided you take enough of it (between 300 and 1,000 mcg daily). 6 7 8 Weak evidence suggests that B 12 supplements may improve sperm activity and sperm count; on this basis, they could be useful for male infertility . 9 Some cases of recurrent miscarriage might be due to vitamin B 12 deficiency. 10 One placebo-controlled, double-blind study, enrolling 49 people with eczema, found benefit with a cream containing vitamin B 12 at a concentration of 0.07%. 11 Topical B 12 is hypothesized to work for eczema by reducing local levels of the substance nitric oxide (not related to nitrous oxide).

On the basis of weak and sometimes contradictory evidence, vitamin B 12 has been suggested for HIV , 12 13 14 15 amyotrophic lateral sclerosis , 16 carpal tunnel syndrome , 17 diabetic neuropathy , 18 multiple sclerosis (MS) , 19 20 21 22 restless legs syndrome , 23 and tinnitus . 24 Some evidence suggests that people with vitiligo (splotchy loss of skin pigmentation) might be deficient in vitamin B 12 , and supplementation along with folate may be helpful. 25 However, the evidence is very weak and not all studies agree. 26 Some alternative practitioners recommend the use of injected vitamin B 12 for Bell’s palsy . However, the only scientific support for this approach comes from one study that was not double-blind. 27 (For information on the importance of a double-blind design, see Why Does This Database Rely on Double-blind Studies? )

Vitamin B 12 is also sometimes recommended for numerous other problems, including asthma , depression , osteoporosis , and periodontal disease , but there is essentially no evidence as yet that it really works.

A double-blind trial of vitamin B 12 for seasonal affective disorder (SAD—a type of depression related to lack to lack of light during the winter) failed to find evidence of benefit. 28 One double-blind, placebo-controlled study of 140 people with mildly low B 12 levels failed to find the supplement helpful for improving mental function and mood. 29 Another study failed to find evidence that vitamin B 12 improved general sense of wellbeing among seniors with signs of mild B 12 deficiency. 30 Although vitamin B 12 has been proposed as a treatment for Alzheimer's disease , this recommendation is based solely on the results of one small, poorly designed study. 31 More recent and better-designed studies found little to no benefit. 32


  1. Marcuard SP, Albernaz L, Khazanie PG. Omeprazole therapy causes malabsorption of cyanocobalamin (vitamin B12) Ann Intern Med. 120(3):211-5.
  2. Saltzman JR, Kemp JA, Golner BB, et al. Effect of hypochlorhydria due to omeprazole treatment or atrophic gastritis on protein-bound vitamin B 12 absorption. J Am Coll Nutr. 1994;13:584-591.
  3. Streeter AM, Goulston KJ, Bathur FA, Hilmer RS, Crane GG, Pheils MT. Cimetidine and malabsorption of cobalamin. Dig Dis Sci. 27(1):13-6.
  4. Aymard JP, Aymard B, Netter P, et al. Haematological adverse effects of histamine H 2 -receptor antagonists. Med Toxicol Adverse Drug Exp. 1988;3:430-448.
  5. Salom IL, Silvis SE, Doscherholmen A. Effect of cimetidine on the absorption of vitamin B 12. Scand J Gastroenterol. 1982;17:129-131.
  6. Elia M. Oral parenteral therapy for B 12 deficiency. Lancet. 1998;352:1721-1722.
  7. McIntyre PA, Hahn R, Masters JM, et al. Treatment of pernicious anemia with orally administered cyanocobalamin (vitamin B 12 ). Arch Intern Med. 1960;106:280-292.
  8. Waife SO, Jansen CJ Jr, Crabtree RE, et al. Oral vitamin B 12 without intrinsic factor in the treatment of pernicious anemia. Ann Intern Med. 1963;58:810-817.
  9. Kumamoto Y, Maruta H, Ishigami J, et al. Clinical efficacy of mecobalamin in treatment of oligozoospermia—results of double-blind comparative clinical study [in Japanese; English abstract]. Hinyokika Kiyo. 1988;34:1109-1132.
  10. Reznikoff-Etiévant MF, Zittoun J, Vaylet C, Pernet P, Milliez J. Low Vitamin B(12) level as a risk factor for very early recurrent abortion. Eur J Obstet Gynecol Reprod Biol. 104(2):156-9.
  11. Stucker M, Pieck C, Stoerb C, et al. Topical vitamin B—a new therapeutic approach in atopic dermatitis—evaluation of efficacy and tolerability in a randomized placebo-controlled multicentre clinical trial. Br J Dermatol. 2004;150:977-83.
  12. Rule SA, Hooker M, Costello C, et al. Serum vitamin B 12 and transcobalamin levels in early HIV disease. Am J Hematol. 1994;47:167-171.
  13. Richman DD, Fischl MA, Grieco MH, Gottlieb MS, Volberding PA, Laskin OL, Leedom JM, Groopman JE, Mildvan D, Hirsch MS. The toxicity of azidothymidine (AZT) in the treatment of patients with AIDS and AIDS-related complex. A double-blind, placebo-controlled trial. N Engl J Med. 317(4):192-7.
  14. Shor-Posner G, Morgan R, Wilkie F, Eisdorfer C, Baum MK. Plasma cobalamin levels affect information processing speed in a longitudinal study of HIV-1 disease. Arch Neurol. 52(2):195-8.
  15. Kieburtz KD, Giang DW, Schiffer RB, et al. Abnormal vitamin B 12 metabolism in human immunodeficiency virus infection. Association with neurological dysfunction. Arch Neurol. 1991;48:312-314.
  16. Kaji R, Kodama M, Imamura A, Hashida T, Kohara N, Ishizu M, Inui K, Kimura J. Effect of ultrahigh-dose methylcobalamin on compound muscle action potentials in amyotrophic lateral sclerosis: a double-blind controlled study. Muscle Nerve. 21(12):1775-8.
  17. Sato Y, Honda Y, Iwamoto J, Kanoko T, Satoh K. Amelioration by mecobalamin of subclinical carpal tunnel syndrome involving unaffected limbs in stroke patients. J Neurol Sci. 231(1-2):13-8.
  18. Ide H, Fujiya S, Asanuma Y, Tsuji M, Sakai H, Agishi Y. Clinical usefulness of intrathecal injection of methylcobalamin in patients with diabetic neuropathy. Clin Ther. 9(2):183-92.
  19. Kira J, Tobimatsu S, Goto I. Vitamin B12 metabolism and massive-dose methyl vitamin B 12 therapy in Japanese patients with multiple sclerosis. Intern Med. 1994;33:82-86.
  20. Goodkin DE, Jacobsen DW, Galvez N, Daughtry M, Secic M, Green R. Serum cobalamin deficiency is uncommon in multiple sclerosis. Arch Neurol. 51(11):1110-4.
  21. Baig SM, Qureshi GA, Minami M. The interrelation between the deficiency of vitamin B 12 and neurotoxicity of homocysteine with nitrite in some of neurologic disorders. Biogenic Amines. 1998;14:1-14.
  22. Reynolds EH. Multiple sclerosis and vitamin B 12 metabolism. J Neuroimmunol. 1992;40:225-230.
  23. O'Keeffe ST. Restless legs syndrome. A review. Arch Intern Med. 156(3):243-8.
  24. Shemesh Z, Attias J, Ornan M, et al. Vitamin B 12 deficiency in patients with chronic tinnitus and noise-induced hearing loss. Am J Otolarygol. 1993;14:94-99.
  25. Montes LF, Diaz ML, Lajous J, et al. Folic acid and vitamin B 12 in vitiligo: a nutritional approach. Cutis. 1992;50:39-42.
  26. Kim SM, Kim YK, Hann S-K. Serum levels of folic acid and vitamin B 12 in Korean patients with vitiligo. Yonsei Med J. 1999;40:195-198.
  27. Jalaludin MA. Methylcobalamin treatment of Bell’s palsy. Methods Find Exp Clin Pharmaco. 1995;17:539-544.
  28. Oren DA, Teicher MH, Schwartz PJ, Glod C, Turner EH, Ito YN, Sedway J, Rosenthal NE, Wehr TA. A controlled trial of cyanocobalamin (vitamin B12) in the treatment of winter seasonal affective disorder. J Affect Disord. 32(3):197-200.
  29. Hvas AM, Juul S, Lauritzen L, Nexø E, Ellegaard J. No effect of vitamin B-12 treatment on cognitive function and depression: a randomized placebo controlled study. J Affect Disord. 81(3):269-73.
  30. Hvas AM, Juul S, Nexø E, Ellegaard J. Vitamin B-12 treatment has limited effect on health-related quality of life among individuals with elevated plasma methylmalonic acid: a randomized placebo-controlled study. J Intern Med. 253(2):146-52.
  31. Martin DC, Francis J, Protetch J, Huff FJ. Time dependency of cognitive recovery with cobalamin replacement: report of a pilot study. J Am Geriatr Soc. 40(2):168-72.
  32. Kwok T, Tang C, Woo J, Lai WK, Law LK, Pang CP. Randomized trial of the effect of supplementation on the cognitive function of older people with subnormal cobalamin levels. Int J Geriatr Psychiatry. 13(9):611-6.


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