The following guidance also includes advice on switching from IM to oral Vitamin B12:
- Individuals with pernicious anaemia or significant neurological symptoms with a clear response to IM B12 treatment should usually continue on IM B12 treatment lifelong
- NHS Lothian policy is for lifelong IM B12 for those who have had bariatric surgery.
- B12 liver stores may last anything from 1 – 11 years, although the consensus suggests 2-4 years, so for individuals previously on B12 treatment it may take a few years for their liver B12 stores to become depleted after treatment cessation.
- Upon treatment discontinuation or a switch from IM to oral treatment it is therefore important to consider whether or not it is appropriate to recheck B12 levels after 6 months, and potentially annually for up to 5 years to allow time for liver stores to become depleted.
- How essential this is, depends on how likely is is that the patient may have undiagnosed pernicious anaemia or another malabsorptive state meaning that over time their B12 levels will once again become depleted. Therefore, for patients with a history of malabsorption, other autoimmune diseases etc this monitoring is more important and the full 5 years of checks would be recommended
- Alternatively, where there has been a clear dietary cause which has now resolved e.g. the patient has discontinued a vegan diet, supplementation can usually be stopped without any further monitoring. This will also apply to many where metformin was identified as a cause, with borderline low levels, and all other tests normal.
