What Is Hyperpyrexia?

Medically Reviewed by Melinda Ratini, DO, MS on June 02, 2021

Normal human body temperature ranges from 97 to 100.4 degrees Fahrenheit (36.5 to 37.5 degrees Celsius). Your body temperature changes during the day and varies throughout your lifetime. When your body temperature goes above 100.4 degrees Fahrenheit (37.5 degrees Celsius), you have a fever — also called pyrexia. So, a very high fever is called hyperpyrexia.

‌Hyperpyrexia is a condition where the body temperature goes above 106.7 degrees Fahrenheit (41.5 degrees Celsius) due to changes in the hypothalamus — the organ in the brain that regulates temperature.

Hyperpyrexia is a life-threatening emergency that demands urgent medical attention. Without prompt proper treatment, hyperpyrexia can lead to long-term complications and death. 

Your body temperature can also increase due to external factors like a high ambient temperature. Your hypothalamus is not involved in such cases. This condition is called hyperthermia, not hyperpyrexia.‌‌

If you have hyperpyrexia, then you may also experience:

If your hyperpyrexia stays on for a long time or if it worsens, then you may show more severe symptoms like:

  • Mild confusion 
  • Headache 
  • Contracted pupils 
  • Vomiting 
  • Diarrhea
  • Reduced urine production 

If hyperpyrexia is prolonged, then you may also show:

  • Extreme confusion 
  • Loss of consciousness 
  • Dry, hot, red skin
  • Widened pupils 
  • Seizures 
  • Rapid shallow breathing

If hyperpyrexia progresses further, it will ultimately lead to organ failure and death. 

Causes of Hyperpyrexia

Hyperpyrexia is not a disease but a symptom of an underlying condition, and it can have many causes. Here are some of the causes: 

Infections.Bacterial, parasitic, or viral infections are the most common cause of hyperpyrexia. Malaria, which is caused by protozoa, is also an important infectious cause of hyperpyrexia 

Intracranial hemorrhage. Intracranial hemorrhage means bleeding in the brain, caused by trauma or stroke. This can affect your hypothalamus, which controls thermoregulation — i.e., body temperature control.

Anesthesia. Hyperpyrexia can occur as a side effect of general anesthesia. Hyperpyrexia due to anesthesia happens when there is an underlying muscle disease. This type of hyperpyrexia is called malignant hyperpyrexia. It is associated with a rapid, sustained increase in body temperature, metabolic acidosis, and generalized muscular rigidity. This condition is often fatal. 

Thyroid storm. A thyroid storm is a rare condition where the body overproduces thyroid hormones. The excess hormones can disrupt the body's temperature regulation and cause hyperpyrexia.‌

Some meds and drugs. Some medicines and drugs can also cause hyperpyrexia, these include:

  • Selective serotonin reuptake inhibitors — or SSRIs
  • Antipsychotics 
  • Recreational drugs like ecstasy 

How Hyperpyrexia Is Diagnosed

Hyperpyrexia is diagnosed using a thermometer. A temperature reading of 106.7 degrees Fahrenheit (41.5 degrees Celsius) or above indicates hyperpyrexia. 

Hyperpyrexia always has an underlying cause, and finding this underlying cause is crucial, but sometimes challenging.

If you have hyperpyrexia, you must seek medical attention as soon as possible. To diagnose the cause of hyperpyrexia, your doctor will analyze your medical and travel history, check your physical condition, and run several tests. These tests may include: 

  • Blood tests — for signs of infection
  • Thyroid function tests — for a thyroid storm 
  • Imaging studies — for intracranial hemorrhage

Depending on your history and presentation, your doctor may suggest further testing.

How Hyperpyrexia Is Treated

As an emergency requiring immediate medical attention, hyperpyrexia must not progress to avoid organ damage and death. While you wait for medical attention, do the following to treat the fever:

  • Remove any tight or extra clothing. 
  • Sponge with tepid water or a cool bath. 
  • Replace fluids through drinking. 
  • Take medication like nonsteroidal anti-inflammatory drugs ( NSAIDs). Don't give aspirin to children aged 19 years or below to avoid Reye's syndrome.

Your doctor will decide on the treatment of hyperpyrexia depending on the underlying cause. If the cause is an infection, then your doctors will treat the infection. If it is caused by anesthesia, your doctor will stop the anesthesia and give you medication to control the fever. If you've ever had hyperpyrexia due to anesthesia, you should tell your doctor or anesthesiologist about it.

Any drug-related hyperpyrexia will need you to immediately discontinue taking the drug and receive supportive care. Hyperpyrexia due to a thyroid storm will require antithyroid drugs. Antipyretic medications like NSAIDs and corticosteroids are used to treat hyperpyrexia caused by intracranial hemorrhage.

WebMD Medical Reference



‌California Poison Control System: "Drug and Medication Related Hyperthemia." 

Comprehensive Therapy: "Malignant Hyperpyrexia."

Journal of Medical Virology: "Hyperpyrexia in Patients with COVID-19."

Singapore Medical Journal: "Hyperpyrexia."

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