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What Is the Difference Between Hyperglycemia and Hypoglycemia?

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By Debra A. Sokol-McKay



Hyperglycemia refers to chronically high blood glucose levels. Most medical professionals define hyperglycemia by using the blood glucose goals that you and your physician have established and combining those goals with the blood glucose target ranges set by the American Diabetes Association.

It's important to understand that you'll probably experience high blood glucose levels from time to time, despite your best efforts at control. As with any chronic disease, talk with your physician and diabetes care team if the pattern of your blood glucose readings is consistently higher or lower than your blood glucose goals.

Persistent hyperglycemia can cause a wide range of chronic complications that affect almost every system in your body. When large blood vessels are affected, it can lead to:

  • Stroke (cerebral vascular disease)
  • Heart attack or Congestive Heart Failure (coronary heart disease)
  • Circulation disorders and possible amputation (peripheral vascular disease)

When smaller blood vessels are affected, it can lead to:

Very high blood glucose levels can also lead to the following acute, life-threatening conditions, both of which require immediate medical attention:

Diabetic Ketoacidosis (or DKA) occurs most frequently in persons with type 1 diabetes. Physical signs and symptoms of DKA include:

  • Hyperglycemia (250 mg/dL or greater)
  • Dry, parched mouth
  • Extreme thirst
  • Frequent urination
  • General weakness
  • Fruity breath
  • Nausea and vomiting
  • Abdominal pain
  • Deep, rapid breathing

Hyperosmolar Hyperglycemic Nonketotic Syndrome (or HHNS) occurs most frequently in elderly persons with type 2 diabetes, especially residents of long-term care facilities. Physical signs and symptoms of HHNS include:

  • Severe hyperglycemia (greater than 600 mg/dL)
  • Dry, parched mouth
  • Extreme thirst (which may gradually disappear)
  • Warm, dry skin that does not sweat
  • High fever (greater than 101 degrees F)
  • Sleepiness or confusion
  • Hallucinations
  • Weakness on one side of the body

Contact your physician if you note any of the above symptoms. Your physician will decide if this is a mild case that can be treated at home or a moderate to severe case that requires hospitalization.

You can reduce your risk factors for complications related to hyperglycemia by doing the following:

  • Maintaining your blood glucose levels within a normal range
  • Keeping your blood pressure under control
  • Controlling your blood fats (cholesterol and triglycerides)
  • Avoiding/stopping smoking
  • Increasing your physical activity
  • Avoiding excess alcohol consumption
  • Developing healthy eating habits and losing weight if necessary


Hypoglycemia refers to dangerously low blood glucose levels that drop below 70 mg/dL. It is an acute complication of diabetes and occurs in individuals who use insulin or specific kinds of oral diabetes medication. If you use oral diabetes medications, ask your physician or diabetes educator whether hypoglycemia should be a concern. Symptoms of hypoglycemia include the following:

  • Sweating
  • Rapid pulse
  • Shakiness, dizziness, weakness
  • Decreased coordination
  • Difficulty concentrating
  • Blurred vision
  • Headache
  • Trouble performing routine tasks
  • Note: Symptoms can vary from person to person and episode to episode.

To treat hypoglycemia, you must immediately:

  • Check your blood glucose level to determine the amount of carbohydrate that is needed to raise your blood glucose to a safe level.
  • Use the 15/15 Rule: Consume 15 grams of carbohydrate (4 ounces of regular juice or soda, 1 tablespoon honey, 2 tablespoons raisins, 7 Life Savers®, 9 Sweet Tarts®, or 3-4 glucose tablets) and retest your blood glucose in 15 minutes. If it is still below 70 mg/dL, you should consume an additional 15 grams of carbohydrate. Following the 15/15 Rule can help avoid over treatment and resulting hyperglycemia.

If you are not planning to have a meal within one to two hours after treating a hypoglycemic reaction, eat a snack containing 15-30 grams of carbohydrate to prevent another episode of hypoglycemia.

If hypoglycemia is not treated immediately, it can result in:

  • Severe confusion and disorientation
  • Unconsciousness
  • Seizures
  • Coma
  • Death

Other tips for managing hypoglycemia include:

  • Keep glucose-containing products close by at all times.
  • Clearly label sugar-free products, in a format of your choosing, to distinguish them from regular products.
  • Make sure you can test your own blood glucose, measure insulin accurately, and determine recommended food portions to help prevent and properly treat low blood glucose.
  • Be sure to wear diabetes identification at all times.

Personal Stories

  • Vivian, Living with Diabetes and Visual Impairment
    Vivian was diagnosed with diabetes twenty years ago, at age 58. Ten years later, she was diagnosed with diabetic retinopathy and spinal stenosis. She talks about how she is living and coping with her diabetes and some of the tools and techniques she uses.

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