Tackling the growing number of people with diabetes is "fundamental" to the future of the NHS, Public Health England (PHE) has warned.
Newly released figures show that 3.8 million adults in England now have the condition - with almost a million (940,000) of those undiagnosed.
The proportion of the adult population with diabetes is expected to rise to one in 10 by 2035 (4.9 million people).
About 90% of cases are Type 2 diabetes - which is linked to being overweight and obese - and are therefore largely preventable, PHE said as it released the new data.
The remainder of cases are Type 1, which usually develops in childhood.
Diabetes can lead to serious complications including limb amputation, kidney disease, stroke and heart attacks.
John Newton, chief knowledge officer at PHE, said: "The number of people with diabetes has been steadily increasing and tackling it is fundamental to the sustainable future of the NHS.
"Diabetes can be an extremely serious disease for those that have it and treating it and its complications costs the NHS almost £10bn a year.
"Developing Type 2 diabetes is not an inevitable part of ageing. We have an opportunity through public health to reverse this trend and safeguard the health of the nation and the future of the NHS."
The new Diabetes Prevalence Model was launched ahead of PHE's conference at Warwick University.
It shows that 9% of people aged 45 to 54 have diabetes, but this rises to 23.8% of those aged over 75.
Diabetes is more common in men (9.6% compared with 7.6% of women) while those of south Asian and black heritage are almost twice as likely to have the disease compared with people from white, mixed or other ethnic groups.
Earlier this year, the charity Diabetes UK used GP practice data to show that, across the entire UK, the number of people with diabetes has tipped over the four million mark for the first time.
Chris Askew, chief executive of Diabetes UK, said of the new data: "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."
The NHS Diabetes Prevention Programme is being rolled out across England.
It aims to identify those most at risk of developing diabetes and offers a referral to a diet, weight loss and exercise programme.
A spokesperson from the Obesity Health Alliance, which is made up of health charities, campaign groups and royal colleges, said: "As being overweight or obese is a high risk factor for developing Type 2 diabetes, it's critical that we as a nation take action to tackle this growing crisis.
"Introducing the soft drinks industry levy and restricting junk food marketing to children will help lower the risk of developing obesity-related health conditions like Type 2 diabetes, cancer and cardiovascular disease."