Your body uses glucose for energy. Glucose metabolism requires insulin, a hormone produced by your pancreas. Here's how normal glucose metabolism works, and what happens when you have diabetes — a disease where your body either can't produce enough insulin or it can't use insulin properly.

The food you eat consists of three basic nutrients: carbohydrates, protein and fat.

During digestion, chemicals in your stomach break down carbohydrates into glucose, which is absorbed into your bloodstream.

Your pancreas responds to the glucose by releasing insulin. Insulin is responsible for allowing glucose into your body's cells.

When the glucose enters your cells, the amount of glucose in your bloodstream falls. If you have type 1 diabetes, your pancreas doesn't secrete insulin — which causes a buildup of glucose in your bloodstream. Without insulin, the glucose can't get into your cells.

If you have type 2 diabetes, your pancreas secretes less insulin than your body requires because your body is resistant to its effect.

With both types of diabetes, glucose cannot be used for energy, and it builds up in your bloodstream — causing potentially serious health complications.