The NHS has spent an estimated £625 million over the past decade on synthetic forms of insulin when the recommended human alternatives, which are considerably cheaper, would have probably been just as effective, according to new research published in BMJ Open.

Over the 10 years, the NHS spent a total of £2,732 million on insulin, with the annual cost rising from £156 million to £359 million to give an increase of 130%, say authors Sarah Holden, Chris Poole and Christopher Morgan of the Cardiff Medicentre at the University Hospital of Wales, and Craig Currie of Cardiff University School of Medicine. The researchers base their findings on an analysis of publicly-available data from the four UK prescription pricing agencies of England, Wales, Scotland and Northern Ireland for 2000-2009, adjusting the costs for inflation and reporting them at 2010 prices.

During the decade, the annual cost of synthetic (analogue) insulin rose from £18.2 million, or 12% of the total, to £305 million, or 85% of the total, while the cost of human insulin fell from £131 million (84% of the total) to £51 million (14% of the total), the researchers find.

On the assumption that all patients prescribed insulin analogues could have been prescribed human insulin instead, the NHS could have saved itself £625 million, according to the authors, and they add that, even if only half of those patients could have been switched, that is still more than £300 million savings for the NHS.

The number of people diagnosed with diabetes in the UK has risen to 2.8 million, around 90% of whom have type 2 disease, and while those with type 1 disease require insulin from the start, those with type 2 diabetes tend to be started on insulin later on, the authors note. Insulin analogues were developed to better mimic the actions of the insulin manufactured by the body but it is not clear if the benefits are sufficient to justify their additional costs, they suggest.

"We know that the rise of insulin analogues has had a substantial financial impact on the NHS, yet over the same period there has been no observable clinical benefit to justify that investment," they say.

"It is likely that there was - and is - considerable scope for financial savings," they conclude, adding that, "most worryingly, the clinical role and safety of insulin for use in people with type 2 diabetes is being questioned."