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High blood sugar in diabetes occurs when the sugar (glucose) level in the blood rises above normal. It is also called hyperglycemia. When you have diabetes, high blood sugar may be caused by not getting enough insulin or missing your diabetes medicine. It may also be caused by eating too much food, skipping exercise, or being ill or stressed.
Unlike low blood sugar, high blood sugar usually happens slowly over hours or days. Blood sugar levels above your target range may make you feel tired and thirsty. If your blood sugar keeps rising, your kidneys will make more urine and you can get dehydrated. Signs of dehydration include being thirstier than usual and having darker urine than usual. Without treatment, severe dehydration can be life-threatening. Over time, high blood sugar can damage the eyes, heart, kidneys, blood vessels, and nerves.
Watch for symptoms of high blood sugar. Symptoms include feeling very tired or thirsty and urinating more often than usual. As long as you notice the symptoms, you will probably 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. Testing lets you see when your blood sugar is above your target range, even if you don't have symptoms. Then you can treat it early.
- Call your doctor if you often have high blood sugar or your blood sugar is often above your target range. Your medicine may need to be adjusted or changed.
- Drink extra water or drinks that don't have caffeine or sugar to prevent dehydration.
How do you prevent high blood sugar emergencies?
Treat infections early
Infections that aren't treated (such as urinary tract infections, pneumonia, and skin infections) can raise your risk for a high blood sugar emergency.
- Know the symptoms of high blood sugar. They include feeling very thirsty, feeling very tired, and urinating more than usual. Post a list of the symptoms in a place where you can see it often, such as on your refrigerator door. Add any symptoms you have noticed that may not be on the list. Make sure other people know the symptoms. Teach them what to do in case of an emergency.
- Check your blood sugar at home often, especially if you are sick or not following your normal routine. If you don't have a blood sugar meter, talk with your doctor about getting one. It is easy to miss the early symptoms, especially if you urinate more than usual but aren't more thirsty. Testing your blood sugar at home will help you know when it is high, even if you don't notice symptoms.
- Teach others (at work and at home) the symptoms of high blood sugar. Teach them to call 9-1-1 if you are unconscious or too sick to check your own blood sugar.
- Wear medical identification. Have a medical alert bracelet or other form of medical jewellery with you at all times. This is very important in case you are too sick or injured to speak for yourself. You can find medical identification at a drugstore or on the Internet.
- If you take insulin, test for ketones, especially if your blood sugar is high.
- Make a plan. Usually people who take insulin need to take extra fast-acting insulin when their blood sugar levels are high. Talk with your doctor about how much to take. This depends on your blood sugar level (sliding scale).
- Take your medicines as prescribed. Don't skip diabetes medicine or insulin doses without first talking with your doctor.
Treat high blood sugar early
The best way to prevent high blood sugar emergencies is to treat high blood sugar as soon as you have symptoms or when your blood sugar is well above your target range (for example, 11.0 mmol/L or higher).
- Follow your doctor's instructions for the steps for dealing with high blood sugar. Post the steps in a handy place at home and work. Make sure other people know what to do if you are unable to treat high blood sugar.
- Keep a record of high blood sugar levels. Write down your symptoms and how you treated them. And take the record with you when you see your doctor.
- Call your doctor. Let your doctor know if you have high blood sugar problems. Your diabetes medicine may need to be adjusted or changed. If you take insulin, your dose of insulin may need to be increased.
Drink plenty of liquids
If your blood sugar levels are above your target range, drink extra liquids. This helps replace the fluids lost through your urine. Water and sugar-free drinks are best. Avoid caffeinated drinks, alcohol, and soda pop. And avoid other drinks that have a lot of sugar, such as fruit juice.
Other Works Consulted
- Bolen S, et al. (2016). Diabetes medications for adults with type 2 diabetes: An update. Comparative Effectiveness Reviews, No. 173 (AHRQ Publication No. 16-EHC013-EF). Rockville, MD: Agency for Healthcare Research and Quality. https://www.effectivehealthcare.ahrq.gov/ehc/products/607/2215/diabetes-update-2016-report.pdf. Accessed April 25, 2016.
- Inzucchi SE, et al. (2015). Management of hyperglycemia in type 2 diabetes, 2015: A patient-centered approach: Update to a position statement of the American Diabetes Association and the European Association for the Study of Diabetes. Diabetes Care, 38(1): 140–149. DOI: 10.2337/dc14-2441. Accessed February 18, 2015.
- Kitabchi AE, et al. (2009). Hyperglycemic crises in adult patients with diabetes. Diabetes Care, 32(7): 1335–1343.
Current as of: July 28, 2021
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Kathleen Romito MD - Family Medicine
Adam Husney MD - Family Medicine
Rhonda O'Brien MS, RD, CDE - Certified Diabetes Educator
David C.W. Lau MD, PhD, FRCPC - Endocrinology
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