Topic Overview

High blood sugar (hyperglycemia) is most often seen in people who have diabetes that isn’t well controlled. The symptoms of high blood sugar can be mild, moderate, or severe.

Mild high blood sugar

If your blood sugar levels are consistently higher than your target range (usually 200 milligrams per deciliter (mg/dL) to 350 mg/dL in adults and 200 mg/dL to 240 mg/dL in children), you may have mild symptoms of high blood sugar. You may urinate more than usual if you are drinking plenty of liquids. Some people who have diabetes may not notice any symptoms when their blood sugar level is in this range. The main symptoms of high blood sugar are:

• Increased thirst.
• Increased urination.
• Weight loss.
• Fatigue.
• Increased appetite.

Young children are unable to recognize symptoms of high blood sugar. Parents need to do a home blood sugar test on their child whenever they suspect high blood sugar.

If you don’t drink enough liquids to replace the fluids lost from high blood sugar levels, you can become dehydrated. Young children can become dehydrated very quickly. Symptoms of dehydration include:

• A dry mouth and increased thirst.
• Warm, dry skin.

Moderate to severe high blood sugar

If your blood sugar levels are consistently high (usually above 350 mg/dL in adults and above 240 mg/dL in children), you may have moderate to severe symptoms of high blood sugar. These symptoms include:

• Blurred vision.
• Extreme thirst.
• Lightheadedness.
• Flushed, hot, dry skin.
• Restlessness, drowsiness, or difficulty waking up.

If your body produces little or no insulin (people with type 1 diabetes and some people with type 2 diabetes), you also may have:

• Rapid, deep breathing.
• A fast heart rate and a weak pulse.
• A strong, fruity breath odor.
• Loss of appetite, belly pain, and/or vomiting.

If your blood sugar levels continue to rise, you may become confused and lethargic. You also may become unconscious if your blood sugar levels are very high.