Understanding glucose reading types
Fasting glucose is measured after at least 8 hours without food or caloric beverages. It reflects basal insulin secretion and hepatic glucose output. In UK/NICE guidance, fasting values of 5.6–6.9 mmol/L suggest impaired fasting glucose (IFG, or pre-diabetes), while ≥7.0 mmol/L on two occasions meets a diagnostic criterion for type 2 diabetes.
Post-meal (postprandial) glucose is typically measured 2 hours after the start of a meal. Values consistently above 7.8 mmol/L (2-hour post-meal threshold) in people without known diabetes suggest impaired glucose tolerance (IGT). Values ≥11.1 mmol/L 2 hours after a 75 g oral glucose load meet another diagnostic criterion for diabetes.