The National Health Service (NHS), the United Kingdom's public health care systems, wasted $976 million during the years 2000-2009 on synthetic forms of insulin, when the recommended human alternatives, which are considerably cheaper, would have been just as effective, based on an analysis of publicly available data from the four UK prescription pricing agencies. Costs were adjusted for inflation and reported at 2010 prices.

Over the 10 year period, the NHS spent a total of £2,732 million on insulin, the annual cost rising from £156 million to £359 million, an increase of 130%.

The number of people diagnosed with diabetes in the UK has risen to 2.8 million, around 90% of whom have type 2 diabetes. Those with type 1 diabetes require insulin immediately but those with type 2 tend to be started on insulin later. Synthetic (analogue) insulins were developed to better mimic the actions of the insulin created by the body, but it has never been clear if there are benefits or if they are sufficient to justify their additional cost, say the authors.

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. The cost of human insulin fell from £131 million, or 84% of total, to £51 million, or 14% of the total.

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

"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 conclude.

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