Blood sugar, or glucose, is the main sugar found in your blood. It comes from the food you eat, and is your body's main source of energy. Your blood carries glucose to all of your body's cells to use for energy. Diabetes is a disease in which your blood sugar levels are too high. Over time, having too much glucose in your blood can cause serious problems. Even if you don't have diabetes, sometimes you may have problems with blood sugar that is too low or too high. Keeping a regular schedule of eating, activity, and taking any medicines you need can help.