High blood sugar (hyperglycemia) in diabetes occurs when the sugar (glucose) level in the blood rises above normal. For a person who has diabetes, high blood sugar may be caused by not getting insulin, missing your diabetes medicine, eating too much food, skipping exercise, or being ill or stressed.

Unlike low blood sugar, high blood sugar usually develops slowly over hours or days. Blood sugar levels well above your target range may make you feel tired and thirsty. If your blood sugar level stays higher than your target range, your body will adjust to that level. If your blood sugar continues to rise, your kidneys will produce more urine and you can become dehydrated. Signs of dehydration include being thirstier than usual and having darker urine than usual. If you become severely dehydrated, you can go into a coma and possibly die. Over time, high blood sugar damages the eyes, heart, kidneys, blood vessels, and nerves.

Unless you fail to notice the symptoms, you usually have time to treat high blood sugar so that you can prevent an emergency. Three things can help you prevent high blood sugar problems:

• Test your blood sugar often, especially if you are sick or not following your normal routine. You can see when your blood sugar is above your target range, even if you don't have symptoms of high blood sugar (increased thirst, increased urination, and fatigue). Then you can treat it early.
• Call your doctor if you have frequent high blood sugar or your blood sugar is consistently above your target range. Your medicine may need to be adjusted or changed.
• Drink extra water or noncaffeinated, nonsugared drinks to prevent dehydration.

 What is a high blood sugar emergency?
 Why do you need to treat high blood sugar?
 How do you prevent high blood sugar emergencies?
 Where to go from here