GCG and diabetes mellitus: As already briefly alluded to, the incretin effect in its strict sense is quantified by performing an oral glucose tolerance test (typically with 75 g of glucose in healthy individuals; for people with diabetes lower amounts can be given, but this complicates the estimation because the magnitude of the effect depends on the amount of glucose ingested) (14, 15) on 1 day, with blood sampling for glucose and insulin and for investigative purposes hormone measurements.