Insulin promotes the uptake of glucose by cells and its storage as glycogen. The insulin and glucose tend to balance out in healthy individuals. In healthy individuals, our cells readily respond to insulin and quickly take up glucose. In many people the body produces insulin, but it is not enough to effectively keep up, and blood sugar rises. Most doctors focus on reading blood sugar levels to diagnose health problems. It turns out that high insulin levels precede high sugar levels, making it an excellent predictive test for disease.