High Blood Sugar (Hyperglycemia)

Too much sugar (glucose) in your blood is called high blood sugar (hyperglycemia). This can lead to a dangerous condition called ketoacidosis. In severe cases, it can lead to fluid loss (dehydration) and coma.

Possible causes of high blood sugar

  • Having a poor treatment plan for diabetes 

  • Being sick

  • Being under stress

  • Taking certain medicines, such as steroids

  • Eating too much food, especially carbohydrates

  • Being less active than normal

  • Not taking enough diabetes medicine

Symptoms of high blood sugar

High blood sugar may not cause symptoms. If you do have symptoms, they may include:

  • Thirst

  • Frequent need to urinate

  • Feeling tired or drowsy

  • Nausea and vomiting

  • Itchy, dry skin

  • Blurry vision

  • Fast breathing and breath that smells fruity 

  • Weakness

  • Dizziness

  • Wounds or skin infections that don’t heal

  • Unexplained weight loss if hyperglycemia lasts for more than a few days 

What to do

Do the following:

  • Check your blood sugar.

  • Drink plenty of sugar-free, caffeine-free liquids such as water. Don’t drink fruit juice.

  • Check your blood sugar again every 4 hours. If you take insulin or diabetes medicines, follow your sick-day plan for taking medicine. Call your healthcare provider if you are not able to eat.

  • Check your blood or urine for ketones as directed.

  • Call your provider if your blood sugar and ketones don't go back to your target range.

  • If the value is high, take your diabetes medicines as prescribed. And check your blood sugar more often. Doses of medicines such as insulin can be increased slightly if blood sugars stay high. But your provider must approve this.

    Woman drinking glass of water.
    When you have hyperglycemia, drink plenty of water or other sugar-free, caffeine-free liquids.

Preventing high blood sugar

To help keep your blood sugar from getting too high:

  • Control stress.

  • When you're ill, follow your sick-day plan. 

  • Follow your meal plan. Eat only the amount of food on your meal plan.

  • Stick to your exercise plan.

  • Take your insulin or diabetes medicines as directed by your healthcare team. Also test your blood sugar as directed. If the plan is not working for you, discuss it with your healthcare provider.

Other things to do

  • Carry a medical ID card or a compact USB drive. Or wear a medical alert bracelet or necklace. It should say that you have diabetes. It should also say what to do in case you pass out or go into a coma.

  • Make sure family, friends, and coworkers know the signs of high blood sugar. Tell them what to do if your blood sugar gets very high and you can’t help yourself.

  • Talk with your healthcare team about other things you can do to prevent high blood sugar.


Special note: Drink plenty of sugar-free and caffeine-free liquids when you feel symptoms of hyperglycemia. Call your healthcare provider if you keep having episodes of high blood sugar.

Online Medical Reviewer: Marianne Fraser MSN RN
Online Medical Reviewer: Raymond Kent Turley BSN MSN RN
Online Medical Reviewer: Robert Hurd MD
Date Last Reviewed: 11/1/2018
© 2000-2021 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.