The NHS has wasted £625 million on synthetic insulin over the past decade, according to a report published today.
The researchers based the figure on savings that could have been made by using human alternatives.
The study, published online in BMJ Open, found that in the last 10 years the NHS spent a total of £2.732 billion on insulin.
The annual cost of synthetic insulin rose from £18.2 million to £305 million while the cost of human insulin fell from £131 million to £51 million.
The Cardiff University report found that - based on the assumption that all patients could have been prescribed human insulin - the NHS could have saved itself £625 million.
Its authors concluded: “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.
“It is likely that there was, and is, considerable scope for financial savings.”