What is high blood sugar?

Having too much sugar in your blood is called high blood sugar, or hyperglycemia.

The target blood sugar range for most people living with type 1 diabetes (T1D) is 70 to 180 mg/dL. Blood sugar is sometimes above this target range during the two hours following meals.

What causes high blood sugar?

Causes of high blood sugar include:

  • Not taking enough insulin for the carbs you eat or drink
  • Stress
  • Illness
  • Medications (like steroids)
  • Hormone changes, including puberty, menstruation, and pregnancy
  • Competitive sports and certain sports like weightlifting
  • Caffeine

Hyperglycemia that occurs when there is not enough insulin in the body can lead to diabetic ketoacidosis, or DKA.  

Signs of high blood sugar

Signs and symptoms of high blood sugar include:

Thirst

Thirst

Frequent Urination

Frequent urination

Trouble Concentrating or Seeing

Trouble seeing or concentrating

Drowsiness or Tiredness From Type 1 Diabetes

Fatigue or tiredness

Long-term high blood sugar can cause additional symptoms:

  • Infections, including yeast infections
  • Unexplained weight loss
  • Blurred vision
  • Cuts or sores that do not heal

Persistent hyperglycemia can also contribute to long-term complications that affect the eyes, heart, kidney, and nerves.

How to treat high blood sugar

High blood sugar is treated with insulin. Every person with T1D has a personalized insulin plan developed in partnership with their diabetes care team.

If blood sugar is above 180 mg/dL, but below 240 mg/dL three hours after the last meal/snack and three hours after the last dose of insulin:

  • Check insulin pump or infusion site for blockages.
  • Take a correction dose of insulin.
  • Drink water and rest.
  • If blood sugar remains high, contact your healthcare provider.

If blood sugar is above 240 mg/dL three hours after the last meal or snack and three hours after the last dose of insulin:

  • Check for ketones in blood or urine. If none are present, follow the steps above.
  • If ketones are trace or small, treat according to the advice provided by your diabetes care team. If ketones are moderate or large, follow the steps above and contact your diabetes care team.
  • If moderate or large ketones are present and the person has symptoms of DKA, they could be experiencing a medical emergency, be in DKA, or be dangerously close to it. Call their diabetes care team and emergency contact immediately. If they cannot be reached, call 911 and stay with them until emergency help arrives.

Treating complications of T1D

A look at the most common type 1 diabetes complications and ways they can be prevented or reduced.


Cardiovascular disease (CVD) is a long-term complication of T1D. CVD includes coronary heart disease, cerebrovascular disease, and peripheral artery disease.


For people living with T1D, eye disease is a troubling reality, but early detection and timely treatment can reduce the risk of blindness by over 95 percent.


Nearly one out of three people with T1D develop kidney disease. Fortunately, most people with T1D and kidney disease don’t end up with kidney failure.