--my experience is not most people's. But 1) I have good insurance coverage (and pay plenty for it), and 2) I work with doctors who I trust and who trust me--or at least know better than to argue with me without a whole lot of citations at their fingertips.

Generally and monetarily (insurance) speaking, unless there is suspicion of impaired glucose tolerance, the baseline fasting blood glucose is a sufficient starting point. But, if there is any suspicion at all--and my suspicious category would be quite broad: anybody over 40, anybody with notable fat deposits around their abdomen or butt (a whole lot of us in the modern world, with our sedentary lifestyle and diet), people with signs of lethargy or immune dysfunction--I would immediately think a savy doc should get a hemoglobin A1C and fasting insulin level. The results here may indicate a need to go on to a glucose tolerance test--but often, these will be enough to show insulin resistance/impaired tolerance. The GTT is for more ambiguous cases; there are people with "normal" fssting blood sugar levels who were diagnosed diabetic due to wild swings during a tolerance test. I started doing them due to weird nature of my acute-onset body-wide bruning idiopathic neuropathy. There would be other unusual indications as well.

I now get them to track hwo I'm doing with my diet/exercise/supplement attempts at keeping my insulin resistance from going any further. I do have diabetes in the family, and I'm approaching 47, and the excess gut is recalcitrant, so I'm being very careful.