Tolbutamide Test

This test is used in the diagnosis of insulinomas. This drug causes production and release of insulin from the pancreas. Normally, when 1g is infused over 2 minutes, it causes a decrease in glucose concentration of around 50%, followed by a return to normal of both insulin and glucose concentration after 3 hours. In 80% of patients with insulinoma, glucose levels remain lower and insulin levels a lot higher for the three hours.