Healthcare professionals should refrain from encouraging patients with type 2 diabetes to combine oral glucose lowering drugs (metformin) with insulin until more research is carried out, it is claimed.

While researchers from the Copenhagen Trial Unit, Steno Hospital, and the Copenhagen University Hospital, said the combination of treatments can lead to better blood sugar control, less weight gain and less need for insulin, they claim more evidence on potential harm caused by the combination is required – specifically around the risks of premature death.

Metformin, the glucose lowering drug, is currently recommended by guidelines for patients with type 2 diabetes starting on insulin. 

The study reviewed 2217 patients in total, all of whom had type 2 diabetes and were over 18 years old.

The reporting of important patient outcomes, such as total mortality and deaths from cardiovascular disease, was found to be “very sparse” among trial data.

“Owing to the risk of severe hypoglycaemic attack increasing with the use of metformin plus insulin, there should be further research on the long term benefits and harms of the combination of the drugs,” warned the researchers.