People over 40 should be checked to see if they are at risk of Type 2 diabetes, with almost two million offered a place on a diet and exercise programme, a health watchdog has said.
New guidance from the National Institute for Health and Care Excellence (Nice) said risk assessments for the condition should be carried out in GP surgeries and pharmacies.
It said people should also be encouraged to test themselves for the condition - which is linked to obesity - in community venues and the workplace.
Anyone attending the free NHS health check with their GP once they hit 40 should be screened for existing Type 2 diabetes or the chance of having it in future, it said.
Meanwhile, pharmacists can screen for the condition and individuals are advised to take a self-assessment test, such as the Know Your Risk quiz on the Diabetes UK website.
Nice said the 1.7 million people who have the highest risk of developing Type 2 diabetes should be offered a place on an intensive lifestyle change programme.
These plans, such as the Healthier You: NHS Diabetes Prevention Programme, offer people a personalised scheme to reduce their risk of Type 2 diabetes including education on healthy eating and lifestyle, help to lose weight and bespoke exercise lessons.
Nice said it was cost-effective to offer this type of help to people with a fasting glucose reading between 5.5 to 6.9 mmol/l, but that prioritisation could be given to people with a higher reading (6.5 to 6.9 mmol/l) due to their increased risk of developing the condition.
The new guidance also sets out ways people can take more exercise and offers advice on healthy eating, such as swapping Bombay mix and crisps for healthier snacks such as unsalted nuts and low-fat yoghurt.
People should also eat more wholegrain bread and cereals, beans and lentils, vegetables and fruit, and swap sausages and burgers for lean meat and fish, the advice says.
Professor Mark Baker, director of the centre for guidelines at Nice, said: "We know that helping someone to make simple changes to their diet and exercise levels can significantly reduce their risk of developing Type 2 diabetes.
"This approach is a cost-effective way of managing an illness that currently costs the NHS around £8.8 billion a year.
"We need to make sure that the people most at risk have access to the care they need."
Some 3.8 million adults in England now have diabetes - with almost a million (940,000) of those undiagnosed.
About 90% of these cases are Type 2 diabetes, which is fuelled by unhealthy lifestyles.
One in 10 adults in the UK is expected to have diabetes by 2035 (4.9 million people).
Diabetes can lead to serious complications including limb amputation, kidney disease, stroke and heart attacks.