Fewer than half of adults are taking advantage of a free NHS midlife MoT, a charity has found.
Only 44% of adults eligible for an NHS Health Check in the last five years has had one, according to analysis by Diabetes UK.
The five-yearly check-up is offered to adults in England aged 40 to 70 to help spot early signs of Type 2 diabetes, stroke, kidney disease, heart disease and dementia.
According to Diabetes UK, between 2013 and 2018, 15.5 million people were eligible to receive an NHS Health Check, but only 6.8 million had one.
The charity said more must be done to encourage people to take part in the scheme.
It said many adults who are found to be at a high risk of Type 2 diabetes through the scheme are referred to the specialist NHS Diabetes Prevention Programme, which helps people to reduce their risk.
Across the UK there are 12.3 million people at increased risk of developing diabetes and knowing their risk could help them prevent the onset of the condition, the charity added.
It is estimated there are around a million people with Type 2 diabetes who have not been diagnosed.
The Diabetes UK analysis also highlighted significant variation across the country, with just one in five eligible adults taking part in the Health Check in some regions compared with almost all in others.
In Walsall, 99% of eligible adults received their Health Check compared with 18% in the East Riding of Yorkshire and Croydon.
Across England, every local authority is required by law to ensure all eligible people in their area are offered a check every five years.
Diabetes UK is urging local authorities to do more to encourage people to participate.
"The success of the programme in certain areas is due to local councils working hard to make it easier for people to attend these free health checks that only take 15 minutes and can help keep people healthy," said Diabetes UK head of policy Robin Hewings.
"It is absolutely vital that all people who are eligible in every area get a health check.
"If left undiagnosed, Type 2 diabetes can lead to devastating complications, including blindness, amputations, stroke and kidney failure, but with the right treatment and support people living with the condition can lead a long, full and healthy life."
if we are to continue to tackle or delay avoidable ill-health such as Type 2 diabetes and cardiovascular disease in England, it is vital that eligible people get checked in order to increase uptake rates
Professor Jamie Waterall, Public Health England's national lead for the NHS Health Check programme, said: "Heart disease, stroke and Type 2 diabetes are among the biggest causes of early death and ill-health in England, but most cases are preventable.
"That's why the continued effort to expand the NHS Health Check programme is so important as it helps identify who is at risk and, more importantly, what they can do about it.
"Public Health England is working hard to support every council to provide these vital checks for people aged 40 to 74 years old."
Nick Forbes, senior vice chairman of the Local Government Association, said: "Councils have spent millions of pounds inviting more than 14 million eligible people to have an NHS Health Check over the last five years, of which around half have taken up the offer.
"However, if we are to continue to tackle or delay avoidable ill-health such as Type 2 diabetes and cardiovascular disease in England, it is vital that eligible people get checked in order to increase uptake rates."
For more information about the risk of developing Type 2 diabetes, visit https://www.diabetes.org.uk/riskscore