Diagnosing diabetes: blood glucose and the role of the laboratory

The hallmark of untreated diabetes mellitus is a raised blood glucose concentration (hyperglycaemia), associated with many other disturbances of blood chemistry, including acid-base and electrolyte imbalance. This has ensured a central role for clinical laboratories in both diagnosis of diabetes and lifelong monitoring of the diabetic patient. That role is the subject of this article. The aim is to explain how blood glucose concentration test results are used to diagnose diabetes. Central to this will be consideration of the new World Health Organization (WHO) criteria for the diagnosis of diabetes, which were introduced to UK diabetic practice in June 2000. The significance of blood glucose and other laboratory blood tests for monitoring the diabetic patient after diagnosis are also discussed.