A GP has developed a way to find up to 500,000 people with potential diabetSimple software can highlight those whose abnormal blood sugar tests have not yet been followed up.
Dr Tim Holt, who led the project, even found six patients who had been missed at his own practice, the British Journal of General Practice reported.
Diabetes UK said early diagnosis was vital to limit diabetes-related damage.
The government is currently looking at ways to increase the amount of health screening carried out at GP practices.
However, the study suggested that blood tests of thousands of patients showing signs of early type II diabetes were already available to doctors - but not being followed up.
The computer software developed by Dr Holt, from the University of Warwick, and colleagues at Nottingham University, looked for patients who had undergone a blood test more than a year ago, and shown some hint of raised blood sugar levels, but who had not been seen by their doctor with diabetes in mind.
BBC NEWS | Health | Software spots 'missed' diabetes