Both hypoglycemia (low blood glucose) and hyperglycemia (high blood glucose) can occur when patients take some oral medications or insulin to treat diabetes. They can occur from taking too much or too little medication or from eating too much or too little food or from excessive exercise. Learning how to manage your diabetes properly is the key to avoiding hypoglycemia and hyperglycemia. Some people may have hypoglycemia without having diabetes, and in some cases it may be diagnosed as a possible precursor to diabetes. In all instances, it's important to learn to manage your diet and exercise to help control blood glucose levels.