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Oral or IM B12

Mon, 08/10/2009 - 3:53pm -- chowe

Some of my elderly patients are reluctant to have monthly shots. Is there a difference between repleting B12 insufficiency with oral as opposed to IM cyanocobalamin?

Response By: 
Carol L. Howe, MD, MLS
Date Posted: 
Tue, 08/11/2009


The following is directly quoted from the "Plain Language Summary" of the Cochrane Review, first published in 2005 and edited and reprinted in The Cochrane Library 2009, Issue 3:

Vitamin B12 deficiency can cause anaemia and neurological complications. Vitamin B12 is rarely prescribed in the oral form in most countries. Two randomised controlled studies were included in this review. The trials recruited a total of 108 participants and followed up 93 of these from 90 days to four months. The evidence derived from these limited studies suggests that high oral doses of B12 (1000 mcg and 2000 mcg) could be as effective as intramuscular administration in achieving haematological and neurological responses. 1(p.2)

Complete Answer


The apex of all the many triangles and pyramids which have been constructed to demonstrate the hierarchy of evidence based medicine is always “systematic reviews and meta analyses,” the gold standard of which is the Cochrane Database of Systematic Reviews.




Levels of evidence pyramid ("Information Mastery: Navigating the Maze." University of Virginia, Claude Moore Health Sciences Library, 2009.)

Levels of evidence pyramid ("Information Mastery:
Navigating the Maze." University of Virginia,
Claude Moore Health Sciences Library, 2009.) from Georgia State University

SUNY Downstate Medical Center. Medical Research Library
of Brooklyn.Evidence Based Medicine Course.A Guide to
Research Methods: The Evidence Pyramid as shown on

Evidence Pyramid.png

pyramid modified from: Navigating the Maze, University of Virginia

Health Sciences Library. From The University of Washington




The database is maintained by the Cochrane Collaboration, established in 1993, a not-for-profit international group comprised primarily of healthcare professionals from over 90 countries “dedicated to making up-to-date, accurate information about the effects of healthcare readily available worldwide.” 2 The Cochrane summaries “are based on exhaustive searches for evidence, explicit scientific reviews of the studies uncovered in the search, and systematic assembly of the evidence, to provide as clear a signal about the effects of a health care intervention as the accumulated evidence will allow.” 3 (p.38)
This writer will thus not have much to add to the “Authors’ Conclusions,” first  published in The Cochrane Library in 2005 and republished in 2009, Issue 3, entitled “Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency.” The “Implications for practice” summary of those conclusions is quoted directly and in full below. There is an equally interesting “Implications for research” summary. Interested readers are referred to the full Cochrane Review. 1

The limited evidence identified in this systematic review shows that high doses of oral vitamin B12 (2000 mcg) daily are as effective as the intramuscular administration (Kuzminski 1998) in obtaining haematological and neurological responses in patients with vitamin B12 deficiency. High doses of oral vitamin B12 (1000 mcg) initially daily and thereafter weekly and then monthly are also as effective as intramuscular vitamin B12 (Bolaman 2003). The included studies also showed limited evidence for a satisfactory haematological, biochemical and clinical short term response for oral B12 replacement in some patients with conditions associated with malabsorption.

Current clinical practice in UK and in most countries is to prescribe vitamin B12 in the intramuscular form for the treatment of vitamin B12 deficiency. This has been the norm for the last 50 years despite several non-randomised studies in the early 1950's demonstrating satisfactory responses to oral treatment and the fact that there is considerable experience in Sweden in using oral vitamin B12. In 1998, the study by Kuzminski et al. (Kuzminski 1998) was the first randomised controlled trial to show that in achieving a satisfactory neurological, haematological and biochemical response, daily high doses of oral vitamin B12 were as effective or even more effective than intramuscular vitamin B12 when treating patients with vitamin B12 deficiency.

Generalised oral vitamin B12 treatment might benefit many patients in terms of fewer visits to health carers and reduced discomfort associated with injections. Nursing time would be released for treating other patients. However, adherence and monitoring will remain important considerations, regardless of route of administration. 1(p.9)

In the “Implications for research” summary, the Cochrane authors discuss the fact that many patients are reluctant to switch to oral B12 because they simply feel better since starting their B12 injections and are wary about changing routines. “This suggests that intramuscular B12 may carry additional psychotropic effects for patients, exceeding those associated with normalisation of serum vitamin B12 levels.” 1(p.9)   Many patients derive benefit from  weekly or monthly visits to their providers for their B12 shots, and conversely, these visits give providers and their staff a quick opportunity to informally assess the wellbeing of these patients, many of whom are elderly and/or frail.

It is also worthwhile  mentioning the commentary on the Cochrane review, by Andrea K. Bial, MD. She reminds U.S. providersin particular that oral B12 is not covered in many prescription formularies, adding a potential financial burden to patients. She reminds us  too that adding oral B12 to the mix of what may already be an excessive number of  medications for many geriatric patients may simply be contributing to the incidence and risks of polypharmacy.

This brings us full circle to a consideration of the meaning of evidence-based medicine (also often referred to as evidence based practice  or evidence-based decision making). The ultimate goal in evidence based medicine is not a one-size-fits-all, or even a one-sized-fits most cookbook recipe formatted to provide quick answers to complex questions but a true integration of scientific studies, patients' individual needs and preferences, and clinicans' willingness to synthesize and integrate the two. As  David L. Sackett, one of the pioneers of Evidence Based Medicine so articulately summarizes:

Evidence based medicine is the conscientious, explicit, andjudicious use of current best evidence in making decisions aboutthe care of individual patients. The practice of evidence basedmedicine means integrating individual clinical expertise withthe best available external clinical evidence from systematicresearch. By individual clinical expertise we mean the proficiencyand judgment that individual clinicians acquire through clinicalexperience and clinical practice. Increased expertise is reflectedin many ways, but especially in more effective and efficientdiagnosis and in the more thoughtful identification and compassionateuse of individual patients' predicaments, rights, and preferencesin making clinical decisions about their care. 5 (p.71)*    

(*Italics mine)

  1. Vidal-Alaball J, Butler CC, Cannings-John R, et al. Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency. Cochrane Database Syst Rev. 2005;(3)(3):CD004655. 
  2. The Cochrane Collaboration Website. The Newcomer's Guide.  Accessed august 10, 2009.
  3. Straus SE, Richardson WS, Glasziou P, Haynes RP. Evidence-based medicine : how to practice and teach EBM. 3rd ed. Edinburgh ; New York: Elsevier/Churchill Livingstone; 2005.
  4. Bial AK. Review: Limited evidence from 2 randomised controlled trials suggests that oral and intramuscular vitamin B12 have similar effectiveness for vitamin B12 deficiency. Evid Based Med. 2006;11(1):9.
  5. Sackett DL, Rosenberg WM, Gray JA, Haynes RB, Richardson WS. Evidence based medicine: what it is and what it isn't. BMJ. 1996.13;312(7023):71-2.