Fasting Plasma Glucose
A blood glucose measurement taken after at least 8 hours of fasting. Fasting glucose ≥126 mg/dL (7.0 mmol/L) is diagnostic for diabetes, and 100-125 mg/dL indicates prediabetes. It is a common secondary endpoint in metabolic peptide drug trials alongside HbA1c.
Technical Context
FPG represents hepatic glucose output in the fasting state — elevated FPG reflects inadequate suppression of hepatic gluconeogenesis and glycogenolysis due to insulin resistance and relative insulin deficiency. Diagnostic criteria: normal <100 mg/dL (5.6 mmol/L), impaired fasting glucose 100-125 mg/dL (5.6-6.9 mmol/L, indicating prediabetes), diabetes ≥126 mg/dL (7.0 mmol/L, confirmed on repeat testing). FPG is measured in venous plasma after ≥8-hour overnight fast. GLP-1 RAs reduce FPG primarily through: suppression of overnight glucagon secretion (reducing hepatic glucose output) and enhancement of basal insulin secretion. Semaglutide typically reduces FPG by 25-40 mg/dL (1.4-2.2 mmol/L) in type 2 diabetes trials.