Vitamin B12 deficiency medical therapy

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Vitamin B12 deficiency Microchapters


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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]


Medical Therapy


Moderate filiform taste bud atrophy thought to be due to a vitamin B12, or iron deficiency‎

Folate deficiency 

Patients with folate deficiency treated with oral folic acid . Standard dosing of oral folic acid is 1 to 5 mg/day orally for 1 to 4 months, or until complete hematologic recovery occurs. The oral route is sufficient even in those with malabsorption.

Vitamin B12 deficiency must be ruled out, and treated if present, before giving folic acid to a patient with megaloblastic anemia, since administration of folic acid may worsen neurologic complications of untreated vitamin B12 deficiency.

Vitamin B12 deficiency

   For patients with permanently decreased ability to absorb dietary vitamin B12 (eg, pernicious anemia, total gastrectomy, surgical removal of the terminal ileum), life-long treatment is necessary. If the cause of the Cbl deficiency can been eliminated (eg, diet, drugs, reversible malabsorption syndrome(s), treatment can be stopped when the Cbl deficiency has been fully reversed and the cause eliminated.

  • Patients should be treated initially with parenteral B12 ( Grade 2B ).it,s important in patients with neurologic complaints, where a goal is to maximize the probability of full neurologic recovery. Although oral B12 appears to be at least as effective as parenteral B12, concerns about patient compliance lead us to prefer the more certain parenteral route.
  • Once the patient's Cbl status has been normalized, maintenance therapy can be performed with parenteral or oral B12.

B12 can be supplemented in healthy people by oral pill[1]; sublingual pill, liquid, or strip; or by injection. B12 supplements are available in forms including cyanocobalamin, hydroxocobalamin, methylcobalamin, and adenosylcobalamin (sometimes called "cobamamide" or "dibencozide").

Vitamin B12 can be given as intramuscular injections of hydroxycobalamin, methylcobalamin, or cyanocobalamin. Body stores (in the liver) are refilled in the first couple of weeks and then maintenance with monthly to quarterly injections throughout the life.

B12 has traditionally been given parenterally to ensure absorption in the dosage of 1 mg qd x 1 wk, then qwk x 1 month, then monthly. However, oral replacement is now an accepted route, as it has become increasingly appreciated that sufficient quantities of B12are absorbed when large doses are given although this is a less efficient path for absorption (1%). This absorption does not rely on the presence of intrinsic factor or an intact ileum. Generally 1 to 2 mg daily is required as a large dose.[2] By contrast, the typical Western diet contains 5–7 µg of B12(Food and Drug Administration (FDA) Daily Value [3]). This method may be more effective than IM Rx, but requires patient compliance.

Hypokalemia, an excessive low potassium level in the blood, is anecdotally reported as a complication of vitamin B12repletion after deficiency. Excessive quantities of potassium are used by newly growing and dividing hematopoeitic cells, depleting circulating stores of the mineral.

It has been appreciated since the 1960s that deficiency can sometimes be treated with oral B12supplements when given in sufficient doses. When given in oral doses ranging from 0.1–2 mg daily, B12 can be absorbed in a pathway that does not require an intact ileum or intrinsic factor. However, with the advent of sublingual and intranasal administration, tablet usage is becoming outdated. [4][5] Oral absorption is limited so regular intramuscular injections or sublingual/intranasal administration of a cobalamin (preferably methyl- or hydroxycobalamin) is necessary to restore systemic stores to physiological levels. Recent research indicates that sublingual administration eliminates a deficiency as well as injections with the advantage of evading the allergy risk.


  1. Vidal-Alaball J, Butler CC, Cannings-John R, Goringe A, Hood K, McCaddon A; et al. (2005). "Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency". Cochrane Database Syst Rev (3): CD004655. doi:10.1002/14651858.CD004655.pub2. PMID 16034940. Review in: Evid Based Med. 2006 Feb;11(1):9
  2. "Effective Treatment of Cobalamin Deficiency With Oral Cobalamin".
  3. "Dietary Supplement Fact Sheet: Vitamin B12". National Institutes of Health: Office of Dietary Supplements. Retrieved 2006-06-06.
  4. Antoinette M. Kuzminski; et al. (1998). "Effective Treatment of Cobalamin Deficiency With Oral Cobalamin". Blood. 92 (4): 1191–1198. PMID 9694707.
  5. Butler CC, Vidal-Alaball J, Cannings-John R; et al. (2006). "Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency: a systematic review of randomized controlled trials". Fam Pract. 23 (3): 279–85. PMID 16585128.

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