In the glucose-insulin regulatory system, insulin secretion oscillates with a period of 50-150 minutes. Over the past decade, several mathematical models have been proposed to model these ultradian oscillations as well as the metabolic system producing them. However these existing models yield profiles deviant from a normal physiological range. We introduce a DDE (delay differential equation) model with two discrete delays for better understanding and more accurately modeling the glucose-insulin dynamics and the insulin secretory oscillations. With the same set of experimental data used to test other existing models, the simulation profiles obtained from this two time delay model fall within a normal physiological range.