Diabetes patients on Metformin to monitor vitamin B12 levels: UK Govt. issues new advice

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