Routine vitamin B12 screening may prevent irreversible nerve damage in type-2 diabetes

Patients with type-2 diabetes, taking metformin, should have their vitamin B12 levels assessed more regularly to avoid irreversible nerve damage, according to a new study presented at the Society for Endocrinology annual conference in Glasgow. The study findings suggest that earlier detection of vitamin B12 deficiency through routine screening of all metformin-treated, type-2 diabetes patients could reduce their risk of developing irreversible, painful and potentially disabling nerve damage.

The increasing incidence of type-2 diabetes is a serious health issue worldwide. Its prevalence is associated with poor diet and unhealthy lifestyle choices, and it is characterised by high blood glucose levels that need to be controlled by medication. Nerve damage in the periphery (e.g. face, limbs, organs) is a common complication of diabetes, with symptoms that range from numbness to pain, and can lead to debilitating loss of balance and co-ordination. Metformin is the recommended and most effective first-line drug for type-2 diabetes but its use has also been linked to vitamin B12 deficiency, which increases the risk of peripheral nerve damage. Despite the irreversibility of peripheral nerve damage, no official guidelines exist on screening vitamin B12 levels in patients treated with metformin.

In this study, Dr Kaenat Mulla and GP colleagues at Hucknall Road Medical Centre, Nottingham conducted an audit of vitamin B12 screening and deficiency among female, metformin-treated, patients with type-2 diabetes at the GP practice. The audit findings indicated that 64% of patients had not had their vitamin B12 levels checked at all, and that 9.6% of patients were deficient but only 6.4% were being treated with vitamin B12.

Dr Mulla states, "Current British Society of Haematology guidelines recommend that vitamin B12 levels are checked only when there is clinical suspicion of deficiency. However, peripheral neuropathy is irreversible and it may be too late once symptoms have developed."

Dr Mulla and her team now plan to extend their audit to determine how best to treat patients found to be vitamin B12 deficient, and to provide further evidence that all type-2 patients on metformin should have their levels checked more regularly, for example at their annual check-up.

Dr Mulla comments, "Our findings indicate that patients with diabetes taking metformin should be checked more frequently and that we need to ensure deficiencies are adequately treated to avoid irreversible nerve damage." However, she also cautions, "Metformin remains the best treatment for type-2 diabetes, these findings should not discourage patients from taking it, but encourage doctors to monitor vitamin B12 levels more routinely, so any deficiency can quickly be treated."