Treating
Pernicious Anaemia

Injections are the preferred method of treating Pernicious Anaemia

Lifelong intramuscular vitamin B12 replacement for people if autoimmune gastritis/Pernicious Anaemia is the cause, or suspected cause, of vitamin B12 deficiency. Continue with lifelong intramuscular injections, even if symptoms have improved or are no longer present1

Frequency

The frequency of injections varies from country to country. In the UK this is usually a 1mg injection every two to three months though many doctors prescribe more frequent injections. In most other countries the maximum time between injections is two months.

The British National Formulary (BNF) states:

For people with neurological involvement
Initially administer hydroxocobalamin 1 mg intramuscularly on alternate days until there is no further improvement, then administer hydroxocobalamin 1 mg intramuscularly every 2 months.
For people with no neurological involvement
Initially administer hydroxocobalamin 1 mg intramuscularly three times a week for 2 weeks, then administer hydroxocobalamin 1 mg intramuscularly every 2–3 months for life.

Those injections used to be given every month in the 1960’s but this was changed to every two months in the 1970’s and to every three months in 1984.

Symptoms could start to improve within 2 weeks, but this may take up to 3 months. It can take much longer for symptoms to disappear altogether; symptoms could get worse initially during treatment, this should improve. 1
The frequency of injections is the most common cause of complaint by members of this Society and when doctors refuse to prescribe more frequent injections the patient often has to find alternative sources in order to supplement more frequently.
Nobody knows why some patients need more frequent injections than others though there are a number of hypotheses as to why this is so. This Society is currently working with a team of researchers to investigate this thoroughly.

For some, the dose, frequency and way vitamin B12 replacement is given may need to be adjusted or changed for it to work properly 1

…the efficacy and cost–effectiveness of oral treatment in wider population-based settings has yet to be established. There are arguments against the use of oral cobalamin in initiation of cobalamin therapy in severely deficient individuals who have poor absorption, especially due to pernicious anaemia.
High dose oral cobalamin would be a reasonable alternative as maintenance in patients unable to tolerate intramuscular injections provided there is good compliance with treatment. On the other hand, some patients may prefer intramuscular injection therapy in order to assure effective treatment.2

Be Aware – taking supplements that contain B12 will affect any tests ordered by your doctor to assess your B12 status. You should not take any supplement before having your B12 assessed and/or having the test to find out if you have the Intrinsic Factor Antibody.

Read our extended information on the Treatment of Pernicious Anaemia:
Treatment of Pernicious Anaemia
Treatment Advanced

  1. NICE Guideline: Vitamin B12 deficiency in over 16s: diagnosis and management March 2024
  2. Devalia V, Hamilton M, Molloy A; Guidelines for the Diagnosis and Treatment of Cobalamin and Folate Disorders; British Journal of Haematology,2014,166,496-513

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