Here in the U.S., two of the top 10 prescribed drugs are diabetes drugs: Lantus and Januvia. That top 10 list is based on number of monthly prescriptions rather than revenue or cost.
Low Carb Diabetic has the details:
“The NHS in England spent £956.7m on drugs last year prescribed by GPs, nurses and pharmacists to treat and manage the condition. That sum represents 10.6% of the cost of all prescriptions issued by NHS primary care services in 2015-16.
The health service now spends more on medication for type 1 and type 2 diabetes than for any other ailment. The number of diabetics across the UK as a whole has recently risen to more than four million and has increased by 65% over the last 10 years.”
Diabetic Mediterranean Diet 