High blood sugar, also known as hyperglycemia, occurs when there is too much glucose in the bloodstream. This condition is often associated with diabetes, a disease that affects how the body processes sugar. Common causes include eating too many carbohydrates, not taking enough insulin, or experiencing stress. Symptoms of high blood sugar can include increased thirst, frequent urination, and fatigue. If left untreated, it can lead to serious complications, such as diabetic ketoacidosis or long-term damage to organs. Monitoring blood sugar levels is essential for managing this condition effectively.