Glucose (sugar) mainly comes from carbohydrates in your food and drinks. It’s your body’s go-to source of energy. Your blood carries glucose to all your body’s cells to use for energy.
When glucose is in your bloodstream, it needs help — a “key” — to reach its final destination. This key is insulin (a hormone). If your pancreas isn’t making enough insulin or your body isn’t using it properly, glucose builds up in your bloodstream, causing high blood sugar (hyperglycemia).