Table 1

FPG for the diagnosis of diabetes

 • Glucose assay easily automated
 • Widely available
 • Inexpensive
 • Single sample
 • Patient must fast ≥8 h
 • Large biological variability
 • Diurnal variation
 • Sample not stable
 • Numerous factors alter glucose concentrations, e.g., stress, acute illness
 • No harmonization of glucose testing
 • Concentration varies with source of the sample (venous, capillary, or arterial blood)
 • Concentration in whole blood is different from that in plasma
 • Guidelines recommend plasma, but many laboratories measure serum glucose
 • FPG less tightly linked to diabetes complications (than A1C)
 • Reflects glucose homeostasis at a single point in time