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High Blood Sugar (Hyperglycemia) in Diabetes

What is high blood sugar?

High blood sugar means that the level of sugar in your blood is higher than normal. High blood sugar can be serious if it’s not treated. If your blood sugar runs too high over time (months or years), it can cause problems with your heart, eyes, kidneys, nerves, and blood vessels. A very high blood sugar can cause life-threatening problems.

The medical term for high blood sugar is hyperglycemia.

What is the cause?

Your body breaks down some of the foods you eat into sugar. You need some sugar in your cells for energy, but too much sugar in your blood is not good for your health. Insulin is a hormone made by the pancreas, which is an organ in your upper belly. Your body uses insulin to help move sugar from the blood into the cells. When your body does not have enough insulin or has trouble using its own insulin, sugar cannot get into your cells and builds up in your blood. Blood sugar that stays high is the main problem of diabetes.

Sometimes you may have high blood sugar even though you are taking diabetes medicine. This can happen for many reasons but it always means that your diabetes is not in good control. Some reasons why your sugar might go too high are:

  • Not taking your diabetes medicine when you should, or not taking the right amount
  • Taking medicines, such as steroids, for other medical problems
  • Taking in too many calories, eating too many carbohydrates, such as foods made mainly with sugar or white flour, or having too many high-sugar drinks
  • Not getting enough physical activity (exercise helps lowers your blood sugar)
  • Being under stress
  • Being sick, including colds, flu, an infected tooth, or a urinary tract infection, especially if you have a fever
  • Having problems with the insulin you are taking–for example, you may need a different type of insulin or the insulin may not be working because it has not been stored properly
  • Having a problem with your insulin pump, if you are using one–for example, the pump is turned off or the catheter has come out

What are the symptoms?

Usually high blood sugar causes no symptoms, especially if it is brief. However, if your blood sugar gets very high and stays that high for a day or longer, you may have symptoms. Symptoms may include:

  • Blurry vision
  • Dry mouth
  • Increased thirst
  • Urinating a lot
  • Feeling tired

Very high blood sugar (600 mg/dL or higher) can cause coma and even death.

How is it diagnosed?

The level of sugar in your blood can be measured with blood tests you can do at home or at your healthcare provider’s office.

When you have diabetes, commonly recommended blood sugar levels are:

  • Morning fasting blood sugar test: 70 to 130 mg/dL. (A fasting blood sugar test should be done before breakfast, after several hours of no food or drink except water.)
  • Blood sugar test 1 to 2 hours after a meal: less than 180 mg/dL
  • Hemoglobin A1C blood sugar below 7

 A1C   Estimated Average Glucose (eAG)
 7     154 mg/dL 
 8     183 mg/dL 
 9     212 mg/dL 
 10     240 mg/dL 
 11     269 mg/dL 
 12     298 mg/dL 

How is it treated?

Very high blood sugar can be a medical emergency. Ask your healthcare provider what a very high blood sugar would be for you. You may need to stay at the hospital to get your blood sugar back to normal, to treat the cause of the high blood sugar, and to treat any problems caused by the high blood sugar, such as dehydration.

High blood sugar caused by medicines you are taking usually goes away when you stop taking the medicine. Never stop taking the medicine without talking to your healthcare provider. Your provider may be able to change the type or amount of medicine you take. Depending on the medicine, it may take days to weeks for your blood sugar to go back to the proper levels.

How can I take care of myself?

Follow your healthcare provider’s directions carefully to keep your blood sugar normal. This usually means you need to:

  • Eat a healthy diet as recommended by your healthcare provider. Ask for a referral to a dietitian if you are not sure what you should be eating.
  • Exercise according to your provider’s recommendation at least 4 to 5 days a week.
  • Take medicine exactly as directed, if any has been prescribed.
  • Check your blood sugar as often as your provider recommends and take your blood sugar records to every checkup. This helps your provider adjust your medicines.
  • Carry a medical ID (such as a card or bracelet) that says you have diabetes.

Ask your healthcare provider:

  • When to call about a high blood sugar level
  • How to take care of yourself if you are sick (Because blood sugar is likely to be higher if you are ill, ask your healthcare provider for a “sick day plan.”)
  • What symptoms or problems you should watch for and what to do if you have them

Make sure you know when you should come back for a checkup. Keep all appointments for provider visits or tests.

Developed by RelayHealth.
Adult Advisor 2015.1 published by RelayHealth.
Last modified: 2015-01-09
Last reviewed: 2015-01-08
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Copyright ©1986-2015 McKesson Corporation and/or one of its subsidiaries. All rights reserved.

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