Diabetes patients on Metformin to monitor vitamin B12 levels: UK Govt. issues new advice
Metformin is one of the most common drug used treat type 2 diabetes mellitus globally. It is also used in patients with prediabetes to help prevent its progression to diabetes. Metformin is available as immediate and modified-release tablets, as well as an oral solution.
Patients on metformin very frequently encounter vitamin B12 deficiency as a common side effect.
UK Government has recently issued advice to check vitamin B12 serum levels in patients being treated with metformin who have symptoms suggestive of vitamin B12 deficiency. It has also advised to consider periodic monitoring for patients with risk factors for vitamin B12 deficiency.
Advice for healthcare professionals:
- metformin can commonly reduce vitamin B12 levels in patients, which may lead to vitamin B12 deficiency
- the risk of low vitamin B12 levels increases with higher metformin dose, longer treatment duration, and in patients with risk factors for vitamin B12 deficiency
- test vitamin B12 serum levels if deficiency is suspected (for example, in patients presenting with megaloblastic anaemia or new-onset neuropathy) and follow current clinical guidelines on investigation and management of vitamin B12 deficiency (for example, see Clinical Knowledge Summary from NICE)
- consider periodic vitamin B12 monitoring in patients with risk factors for vitamin B12 deficiency (see list of risk factors in article)
- administer corrective treatment for vitamin B12 deficiency in line with current clinical guidelines; continue metformin therapy for as long as it is tolerated and not contraindicated
- report suspected adverse drug reactions associated with metformin on a Yellow Card
Advice for healthcare professionals to give to patients and carers:
- if you are taking metformin, seek medical advice if you develop new or worsening symptoms of extreme tiredness, a sore and red tongue, pins and needles, or pale or yellow skin-these can be signs of low vitamin B12 levels
- you may need blood tests to find out the cause of your symptoms; these symptoms can also be caused by diabetes or other unrelated health issues
- you can keep taking metformin while vitamin B12 levels are being corrected
- do not stop your treatment without first discussing this with your doctor
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