The rising problem of obesity has helped to make diabetes treatments the biggest drug bill in primary care, with almost £600 million of medicines prescribed by doctors last year, according to the NHS Information Centre.

Analysts said that young people contracting the condition, which is often associated with obesity, were helping to push up costs as doctors tried to improve their long-term control of the disease and prevent complications.

A total of 32.9 million diabetes drugs, costing £599.3 million, were prescribed in the past financial year. In 2004-05 there were 24.8 million, costing £458 million.

More than 90 per cent of the 2.4 million diabetics in England have type 2 diabetes, with the remainder suffering from type 1, the insulin-dependent form of the disease caused when the body’s immune system destroys insulin-producing cells in the pancreas. There are thought to be 500,000 undiagnosed cases of diabetes.

While rates of type 1 have shown slight increases in recent years, type 2 has risen far more rapidly — a trend linked to the increasing number of people who are overweight or obese. Almost one in four adults in England is obese, with predictions that nine in ten will be overweight or obese by 2050. Obesity costs the NHS £4.2 billion annually. This year the Government started a £375 million campaign aimed at preventing people from becoming overweight by encouraging them to eat better and exercise more.

An NHS Information Centre spokeswoman who worked on the report, which was published yesterday, said that diabetes was dominating the primary care drug bill as better monitoring identified more sufferers and widely used medications such as statins became cheaper. She said that the data suggested a growing use of injectable insulin in type 2 diabetes care, which was helping to push up costs.

Doctors agreed that more expensive long-acting insulin, which can cost about £30 per item, was being used more often, as well as more expensive pills and other agents.

The report, an update of the centre’s June publication Prescribing for Diabetes in England, shows that the number of insulin items prescribed last year rose by 300,000 to 5.5 million, at a total cost of £288.3 million. It marked an 8 per cent rise on the £267 million spent in the previous year. However, while the number of anti-diabetic drugs, which are mostly in tablet form, also rose, the cost dropped slightly to £168.1 million.

“Type 2 is increasing. We are seeing it in younger people, and because it is a progressive disease people are needing an increasing number of interventions as time goes by,” the spokeswoman said, adding that long-acting insulins such as Glargine were now common. “For people who are struggling to control their type 2 diabetes it makes sense, but it is quite a big clinical change from five or ten years ago.”

Other anti-diabetic items, such as use of the subcutaneous injection exenatide, have also increased and cost £14.3 million.

Laurence Buckman, chairman of the British Medical Association’s general practice committee, said that he had observed a trend with drugs such as exenatide, which costs £80 per item. He said that younger patients could start on cheaper tablets such as metformin, which costs £3.70 per box, but were needing increasingly sophisticated treatments to keep their condition in check.

“You are talking about an ever larger number of people getting a large range of drugs to reduce long-term complications. Type 2 is a common chronic illness that is getting commoner. It’s in everyone’s interest to treat people early and with the most effective drugs, and these are the more expensive tablets and long-acting insulins,” he said. By Sam Lister, The Times.