All adults aged between 40 and 70 should be screened for the condition, say researchers, as receiving help earlier could reduce risk of complications from the disease.
Currently, only high-risk adults are offered a blood test to check for the presence of type two diabetes during the National Health Service check, the academics said.
But if every adult was offered the test, undiagnosed cases of the condition could be identified two years earlier, 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 faster if the blood test was routinely used in the NHS check.
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They looked at information on people taking part in the UK Biobank study who had been given a HbA1c blood test when they signed up.
This was then linked to GP records to see whether patients already had a diagnosis of diabetes.
About 7.3 per cent of those who had the test already had the condition diagnosed.
Among 167,000 people who did not have a diagnosis of type two diabetes, about 1 per cent had undiagnosed diabetes.
People taking part in the study were tracked for 10 years.
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“Our population-based study shows that HbA1c screening in adults aged 40–70 years can reduce the time to diabetes diagnosis by a median of 2.2 years, compared with routine clinical care,” the authors wrote.
“The findings support the use of HbA1c screening to reduce the time for which individuals are living with undiagnosed diabetes.”
The researchers said there are about 25 million adults aged 40-70 years living in the UK today without a diagnosis of diabetes.
So if the findings can be extrapolated, up to 250,000 adults in this age group have undiagnosed diabetes, which could be detected by HbA1c-based screening, they said.
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“This research provides clear evidence of delays in the diagnosis of type two diabetes and suggests that tests of average blood sugar levels at population level could help to pick up cases of type two diabetes sooner than they otherwise would be," said Lucy Chambers, head of research communications at Diabetes UK.
“Early diagnosis is the best way to avoid the devastating complications of type two diabetes, and offers the best chance of living a long and healthy life with type two diabetes.
“Type two diabetes can sometimes go undetected for up to 10 years, which can lead to serious complications.
“While the symptoms of type two diabetes can sometimes be tricky to spot in the early stages, it’s important to know the signs to look out for, including being thirsty, unexplained weight loss, tiredness and passing urine more often.
"If you notice anything unusual, speak to your GP. “