Computer simulation of hyperinsulinaemic euglycaemic clamp studies (HECS) using a novel model of insulin kinetics shows that a priming dose of insulin should be in the form of a 10-min-long infusion at a rate six-fold higher than the intended insulin infusion rate in patients with non-insulin-dependent diabetes mellitus. Using this priming regimen, glucose uptake attains equilibrium within 90 min. Two alternative priming regimens: a priming bolus and a monoexponential-decay priming infusion, also result in equilibrium of glucose uptake within 90 min, but give higher transients of plasma insulin concentration. However, with no priming, or if a conventional priming regimen is used, glucose uptake at 90 min rises to only around 80% of its equilibrium value. We conclude that priming of insulin is essential to attain steady state of glucose uptake within 90 min of HECS and that conventionally used priming regimens result in an underestimation of glucose uptake.