New estimates suggest that around 250,000 middle-aged adults do not know they have type 2 diabetes.
The researchers said all adults aged 40-70 should be screened for the disease – with early help reducing the risk of complications from the disease.
The researchers said only high-risk adults are currently being offered a blood test to check for type 2 diabetes during an NHS health check.
But if every adult were offered the test, undiagnosed cases of the disease could be identified two years earlier, they added.
“Screening can detect cases of undiagnosed diabetes earlier than symptomatic or incidental diagnosis, allowing for earlier intervention that may reduce the risk of diabetes complications,” the research team wrote in Diabetologia, the journal of the European Association for the Study of Diabetes.
The team, led by Dr Katie Young from the University of Exeter, wanted to assess whether people would get a diagnosis more quickly if the blood test was routinely used in the NHS check-up – also known as MoT in middle age.
They looked at information about people taking part in the UK Biobank trial who were given an HbA1c blood test at registration.
This was then linked to the GP records to see if the patients had already been diagnosed with diabetes.
About 7.3% of those who passed the test had already been diagnosed with the disease.
Of the 167,000 people who were not diagnosed with type 2 diabetes, approximately 1% had undiagnosed diabetes.
The people in the study were followed for 10 years.
The researchers found that the average time to diagnosis was 2.2 years.
“Our population-based study shows that HbA1c screening in adults aged 40–70 years can reduce time to diabetes diagnosis by a median of 2.2 years compared to routine clinical care,” the authors wrote.
“The findings support the use of HbA1c screening to shorten the lifespan of people with undiagnosed diabetes.”
The researchers found that there are currently around 25 million adults aged 40-70 in the UK who have not been diagnosed with diabetes.
So if the results can be extrapolated, up to 250,000 adults in this age group have undiagnosed diabetes that can be detected with HbA1c-based screening, they said.
Lucy Chambers, head of research communications at Diabetes UK, said: “This study provides clear evidence of delays in diagnosing type 2 diabetes and suggests that population-level average blood sugar testing could help detect cases of type 2 diabetes earlier than otherwise. .
“Early diagnosis is the best way to avoid the devastating complications of type 2 diabetes and gives you the best chance of living a long and healthy life with type 2 diabetes.
“Type 2 diabetes can sometimes go undetected for up to 10 years, which can lead to serious complications.
“While the symptoms of type 2 diabetes can sometimes be difficult to spot in the early stages, it’s important to know the symptoms to look out for, including thirst, unexplained weight loss, fatigue and more frequent urination. If you notice anything unusual, talk to your GP. “