A fasting glucose test [FPG], an Oral
Glucose Tolerance
Test [OGTT], and an random plasma
glucose test [RPG]
measures you glucose level at the time of the test. All three provide the doctor an insight on your glucose levels. They don't lie, only humans do. An A1c [hemoglobin A1c], on the other hand, looks back three months. The results are given in % [percentile]. New red blood cells live on average of three months. Excess sugar binds to these cells until the cell dies off.