Fasting insulin > 30 microU/mL (upper limit of normal) is hyperinsulinemia / T2DM.
However, Kraft's cumulative study of 14,384 OGTT with insulin assays showed that < 8% of those with hyperinsulinemia / T2DM have fasting insulin > 30 microU/mL.
If fasting insulin of >30 microU/mL were used as cutoff for T2DM diagnosis, 92% T2DM cases would be missed. Therefore, 2 hr post 75g glucose insulin level is more sensitive in detecting early T2DM.