Insulin is a chemical messenger that your body produces to help turn the food you eat into energy. After you eat a meal, especially one with carbohydrates like bread or pasta, your blood fills with sugar from that food. Insulin acts like a key that unlocks your cells so they can absorb that sugar and use it for energy, whether you're running around at recess or concentrating on a math problem.

Your pancreas, an organ behind your stomach, makes insulin automatically throughout the day. In people with diabetes, the body either doesn't make enough insulin or can't use it properly. Without working insulin, sugar builds up in the blood instead of getting into cells where it's needed. People with diabetes may need to inject insulin or take medicine to help their bodies manage blood sugar levels.

Scientists Frederick Banting and Charles Best discovered insulin in 1921, transforming diabetes from a fatal disease into a manageable condition. Today, millions of people with diabetes use insulin to stay healthy and active.