Half a million adults may have type 2 diabetes without even realising it, a study has revealed.
Scientists analysed blood samples from 200,000 Britons aged between 40 and 70.
They found that 2,000 of them had very high blood sugar levels, indicating they had diabetes, but had not yet been diagnosed with the condition.
This suggests that 1 per cent of the UK – over half a million people – could be living with type 2 diabetes without knowing it.
The study by the University of Exeter suggested that a national screening programme should be brought in to improve diagnosis.
Experts said symptoms of type 2 diabetes, which include frequently going to the toilet, being thirsty and feeling tired, are easy to miss, especially during the early stages.
Co-author Dr Katherine Young, said: ‘As people can have type 2 diabetes for many years without symptoms, diagnosis may be delayed, increasing the risk of complications.
‘Our study shows that population-level screening could identify cases of type 2 diabetes far earlier and potentially reduce complications.’
Diabetes is mostly diagnosed by measuring the level of HbA1c, a haemoglobin which is chemically linked to sugar, in the bloodstream.
Dr Young said: ‘We identified that screening by HbA1c would have identified an extra 1 per cent of a population aged 40-70 years as having undiagnosed diabetes.’
She added: ‘This screening diagnosis would have been approximately two years before a clinical diagnosis was made.’
The authors analysed blood samples from over 200,000 patients on the UK Biobank database and compared their blood sugar levels to GP records.
Men over the age of 60, especially if they were obese, were more likely to have undiagnosed diabetes than women, the researchers found.
Britain’s obesity epidemic has led to soaring levels of type 2 diabetes. Two-thirds of adults are either obese or overweight, one of the highest rates in the Western world.
More than 4million people in the UK now have diabetes, compared with just 1.8million in 1998.
Around 90 per cent of people with diabetes have type 2, which is mostly caused by obesity.
Diabetes occurs when blood sugar levels rise to risky heights and can lead to fatal complications, including amputations, sight loss, stroke and heart disease.
Type 1 diabetes is an unpreventable autoimmune disease that usually develops in childhood, but type 2 is mostly caused by poor diet.
Dr Faye Riley, of Diabetes UK, said: ‘Type 2 diabetes can go undetected for years and this research flags that all too often, people can have the condition but not know it.’
The research was presented at the Annual Meeting of the European Association for the Study of Diabetes.