What is Hyperglycemia?

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  • What is hyperglycemia?
  • What causes hyperglycemia?
  • What are the symptoms?
  • How to prevent hyperglycemia?

Hyperglycemia is a medical condition characterized by high blood glucose levels. The condition is primarily caused by significantly lower blood insulin levels or improper functioning of insulin.

What is hyperglycemia?

Hyperglycemia is characterized by fasting and 2-hour postprandial blood glucose levels of more than 125 mg/dl and 180 mg/dl, respectively. A patient with a fasting glucose level of 100 – 125 mg/dl is considered pre-diabetic; whereas, a patient with a fasting glucose level of more than 125 mg/dl is considered diabetic.

If left untreated, hyperglycemia can lead to serious complications, including damage to the eyes, kidneys, heart, blood vessels, and nervous system. In some extreme cases, it can lead to a diabetic coma.

Diabetes insulin hypoglycemia or hyperglycemia diagram. Image Credit: Kolonko / Shutterstock

What causes hyperglycemia?

Impaired glucose homeostasis is the main causative factor for hyperglycemia, which primarily occurs due to an imbalance between glucose production in the liver and its uptake and utilization in the peripheral cells.

Insulin is a hormone responsible for cellular glucose uptake and maintenance of normal blood glucose levels. An abnormal increase in blood glucose level occurs when insulin is produced in lesser amount by the pancreatic cells (type 1 diabetes), or when the body becomes resistant to normal insulin effects (type 2 diabetes).

There are several risk factors that can increase the chance of developing hyperglycemia. People with diabetes can be affected by hyperglycemia if they are not using the proper dose of diabetes medications. Eating a high quantity of carbohydrate-rich foods can also lead to a sudden increase in blood glucose levels.

The presence of certain illnesses/infections or emotional distress can increase the risk of hyperglycemia because hormones secreted in the body to fight such conditions can significantly increase the blood glucose level.

A family history of diabetes or a history of gestational diabetes can increase the risk of hyperglycemia. Moreover, people with hypertension, hyperlipidemia, or polycystic ovarian syndrome are at higher risk. Another significant risk factor for hyperglycemia is an inactive lifestyle and being overweight.

What are the symptoms?

For effective management of hyperglycemia, it is important to recognize its primary signs and symptoms. The condition is associated with high blood glucose levels as well as the presence of glucose in urine. The most common early symptoms include fatigue, headache, blurred vision, frequent urination, and increased thirst.

If left untreated, chronic hyperglycemia can lead to abnormal accumulation of toxic acids called ketones in the blood and urine, which is medically termed as ketoacidosis. Due to the absence of insulin, the cells cannot use glucose as an energy source; instead, the cells breakdown fats to get energy and subsequently produce ketones as byproducts. The symptoms of ketoacidosis include nausea/vomiting, shortness of breath, fruity-smelling breath, abdominal pain, weakness, weight loss, dry mouth/skin, confusion, and coma.

A long-term presence of hyperglycemia can also be associated with frequent infections and a slower rate of wound healing.

How to prevent hyperglycemia?

The best way to prevent hyperglycemia-related complications is to monitor blood glucose levels daily using a glucose meter. For diabetic patients, it is vital to properly consume the prescribed medicines (insulin shots or glucose-controlling medicines) and follow the diet plan. Diabetic patients should also follow a strict physical activity regimen. However, if ketones are present in the blood or urine, exercise is not recommended as it can further increase the ketone level.

According to the American Diabetes Association, the recommended target blood glucose levels for diabetic patients include:

  • Fasting blood glucose level: 80 – 130 mg/dl
  • 2-hour postprandial blood glucose level: less than 180 mg/dl
  • If blood glucose level goes above 240 mg/dl, doctors generally recommend urine tests to check the glucose level in the urine.

Also, doctors may ask for the HbA1C test, which is conducted to check glucose tolerance. This test measures the percentage of glucose attached to hemoglobin and gives an average blood glucose level for past 2 -3 months. An HbA1C value of 7% or lower indicates that the blood glucose level is relatively well controlled.

In case of severe hyperglycemia, emergency treatments may be required, including fluid replacement, electrolyte replacement, or insulin therapy. A fluid replacement treatment is necessary to rehydrate the body and dilute the glucose in the blood.

Electrolyte replacement is required as the absence of insulin can decrease the electrolyte level in the blood. Electrolytes are necessary for the proper functioning of the heart, muscles, and nerves.

An insulin therapy, which is performed by injecting insulin through veins, is required to immediately prevent the formation and accumulation of ketones in the blood.    


  • NCBI. 2019. Hyperglycemia. https://www.ncbi.nlm.nih.gov/books/NBK430900/
  • Mayo Clinic. 2018. Hyperglycemia in diabetes. www.mayoclinic.org/…/syc-20373631
  • Cleveland Clinic. 2017. Hyperglycemia. my.clevelandclinic.org/…/9815-hyperglycemia-high-blood-sugar
  • American Diabetes Association. 2019. Hyperglycemia. www.diabetes.org/…/hyperglycemia
  • Medline Plus. 2016. Hyperglycemia. https://medlineplus.gov/hyperglycemia.html

Further Reading

  • All Hyperglycemia Content
  • Hyperglycemia Causes
  • Hyperglycemia Effects
  • Hyperglycemia Symptoms

Last Updated: Mar 16, 2020

Written by

Dr. Sanchari Sinha Dutta

Dr. Sanchari Sinha Dutta is a science communicator who believes in spreading the power of science in every corner of the world. She has a Bachelor of Science (B.Sc.) degree and a Master's of Science (M.Sc.) in biology and human physiology. Following her Master's degree, Sanchari went on to study a Ph.D. in human physiology. She has authored more than 10 original research articles, all of which have been published in world renowned international journals.

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