A total of 940,000 adults in England are unaware that they have the condition, according to data from a tool launched by Public Health England (PHE) that estimates type 1 and type 2 diabetes prevalence.
The figures published by PHE show that 9% of adults currently have diabetes, a figure expected to rise to around 10% over the next two decades.
Nearly 90% of cases are potentially preventable type 2 diabetes, PHE said, highlighting the need to support patients through NHS health checks and schemes such as the diabetes prevention programme, which offers referral for diet, weight loss and physical activity advice. Type 2 diabetes costs the NHS £8.8bn a year.
Diabetes UK chief executive Chris Askew said: 'These new estimates clearly show the scale of diabetes and the huge impact on people living with the condition. Too often they only find out they have the disease after they have developed serious complications, such as heart or kidney disease, or foot problems which can lead to amputations.
'Avoiding or delaying such devastating complications depends on people getting diagnosed earlier, so they get help and support to manage their condition well. We urge people over 40 to attend their NHS Health Check when invited. We also want people to take the necessary steps to find out their risk of developing Type 2 diabetes, such as using Diabetes UK’s online Know Your Risk tool.'