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

Symptoms of mild high blood sugar include:

• Increased thirst and urination, especially at night.
• Warm, dry skin.

Symptoms of moderate high blood sugar include:

• Dizziness or weakness when sitting or standing.
• Dark, concentrated urine in decreasing amounts.
• Gradual blurring of vision.

Symptoms of severe high blood sugar include:

• A rapid heart rate with a weak pulse.
• Drowsiness and difficulty waking up.
• Increased weakness.
• Sometimes, loss of consciousness.

If your blood sugar levels remain high, such as above 250 mg/dL, and you become dehydrated, you are at risk of getting a life-threatening condition called hyperosmolar state or diabetic ketoacidosis. These are both medical emergencies.

Get medical help immediately if you have symptoms of diabetic ketoacidosis:

• Rapid, deep breathing
• Fruity breath odor
• Loss of appetite, belly pain, and vomiting