Malignant hyperthermia (MH) is a fast and harmful rise in body temperature.


This problem is often caused by a faulty gene. People who have the gene have malignant hyperthermia susceptibility.

MH can be triggered by certain medicines, mainly anesthesia and muscle relaxers.

Risk Factors

This problem is more common in young adults and men. Having others in the family with this problem also raises the risk a person will have it.


Problems may start after medicine is given. A person may have:

  • Fever higher than 105°F (40.6°C)
  • Stiff muscles
  • Muscle spasms, mainly in the face
  • Fast breathing
  • Fast or irregular heartbeat
  • Dark urine
  • An uneven skin color
Muscle Fibers
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MH is an emergency. It is diagnosed based on symptoms and recent anesthesia.

MH susceptibility may be suspected based on a person's medical and family history. Genetic testing and a muscle biopsy may be done to confirm it.


Any medicine causing this problem will be stopped or changed. Medicine may also be given to lower body temperature.

Emergency care will be needed, such as:

  • Oxygen therapy
  • Ending or postponing surgery
  • Supportive care and monitoring


A person with MH susceptibility or a family history of MH should share this information with their doctors, mainly before any surgery or procedure.

Revision Information

  • Reviewer: EBSCO Medical Review Board James P. Cornell, MD
  • Review Date: 09/2019 -
  • Update Date: 12/03/2019 -