Vitamin B12: to inject or not to inject?

Why treating vitamin B12 deficiency with intramuscular injections could be a waste of nurses’ time

Why treating vitamin B12 deficiency with intramuscular injections could be a waste of nurses’ time

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Vitamin B12 deficiency is treated with injections given by district and general practice nurses based on the understanding that people are unable to absorb B12 orally. But does this stand up to scrutiny or could we offer people a more effective mode of treatment?

There is evidence that high dose B12 can be taken orally in many instances, which can mean nurses are not needed to administer the doses – and the patient does not have to suffer the pain of intramuscular injections.

B12 is absorbed in the small intestine (Chan et al 2016) and subcutaneous injections can be bought online, but they are not available on prescription. There has been little encouragement for people to manage their own injections of B12, unlike other medications for conditions such as rheumatoid arthritis or diabetes.

High dose oral B12 is not licenced in the UK

In Sweden and Canada, injections of B12 are not the standard treatment for B12 deficiency, instead 1,000 micrograms are taken daily with good effect (Butler et al 2006). This would be a step forward, but these high doses are not licenced for use in the UK.

In a 2003 study at a Birmingham general practice, patients were given high dose (1,000 micrograms) cyanocobalamin instead of injections and were followed closely for 18 months (Nyholm et al 2003). It was found that none of the 40 patients’ B12 levels dropped throughout this period and there was no indication to change back to B12 by intramuscular injection. The oral dose was donated by the pharmaceutical company for the purpose of the study and the medication is currently available online.

Oral vitamin B12 is more expensive than the injection, however when nurses’ costs are included the price is lower. A study by Vidal-Alabell et al (2009) compared the costs of intramuscular and oral vitamin B12 in primary care. At the time of the study, it was calculated that the cost of treating a patient in general practice was between £55 and £99 a year, in contrast to the cost of using high-dose oral therapy which was £25 a year.

Recommendations for practice nurses

The way forward consists of blood tests, accurate assessment and use of audits in the primary care setting to find out who needs to continue with intramuscular injections and who can be managed on dietary advice, correction of other conditions or oral supplements. For many people, B12 injections are not needed, so it is essential to first find the cause of their low B12 levels.

Clinicians can request a test for active or serum levels of B12 using a blood form. The active blood test is known as Holo TC (holotranscobalamin). This test is used in some laboratories instead of serum B12 as it is considered more sensitive. If a low B12 reading is found, a further methylmalonic acid (MMA) test can be conducted. This method is a more consistent way of diagnosing pernicious anaemia and enables a more intensive treatment to be started earlier.

MMA levels can be raised for reasons other than pernicious anaemia, including renal disease, haemoconcentration and small bowel overgrowth. Another test that is often used to confirm pernicious anaemia is homocysteine. These tests are preferable to gastric parietal antibodies and intrinsic factor, which have been used in the past.

Improving assessment and diagnosis for vitamin B12 deficiency

Primary care staff can do an improved assessment to understand why the serum or active B12 tests are low. The levels may be lower if the patient is pregnant or has been taking certain medications for a long time. They can also be affected by alcohol intake, glossitis, hypothyroid disorder, coeliac or Crohn’s disease.

The British Haematology Society recommends auditing people with low B12 and folate orders. An audit can help primary care staff find out if the right blood tests have been conducted. These tests ensure that nurses can discuss with the patient whether to stop treatment with injections and re-test. Oral supplements can be substituted in some cases.

The Pernicious Anaemia Society states that there are people who have pernicious anaemia who have had to have multiple tests before the condition is confirmed (Hopper et al 2014). The British Haematology Society (2019) acknowledges that there is no gold standard for a straightforward diagnosis.

There is evidence that low B12 is a sign of fatigue and other conditions, but in most instances, B12 injections need to be used for people who have no other way of managing the deficiency and have developed pernicious anaemia (Nyholm 2003).


  • Butler C, 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. Family Practitioner. 23, 3, 279.
  • British Society for Haematology (2019) Diagnosis of B12 and Folate Deficiency.  
  • Chan C, Low L, Lee K (2016) Oral vitamin B12 replacement for the treatment of pernicious anaemia. Frontiers in Medicine. 3, 38.
  • Devalia V, Hamilton M, Molloy A (2014) Guidelines for the diagnosis and treatment of cobalamin and folate disorders. British Journal of Haematology. 166, 4, 496-513.
  • Nyholm E, Turpin P, Swain D et al (2003) Oral vitamin B12 can change our practice. Postgraduate Medical Journal. 79, 218-220.
  • Vidal-Alaball J, Butler C, Potter C (2009) Comparing costs of intramuscular and oral vitamin B12 administration in primary care: a cost-minimization analysis. European Journal of General Practice. 12, 4. 

Alexandra Murrell is a nurse practitioner at Hurley Medical Bank and a health studies lecturer at the London campus of the University of West Scotland

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