When Is a High Body Temperature Considered Serious?

When you’re exposed to very hot outdoor temperatures you can experience heat exhaustion, because you lose a lot of fluids and electrolytes.
When Is a High Body Temperature Considered Serious?
Maricela Jiménez López

Written and verified by the doctor Maricela Jiménez López.

Last update: 27 May, 2022

The normal temperature range for the human body is between 97.6 and 100.0ºF. To maintain a healthy temperature, it’s important to be able to adapt to your environmental surroundings. When your body’s ability to deal with heat is lost, however, your body temperature may rise.

When you have a high body temperature, it causes your blood vessels to dilate. Thus, it transports excess heat to the surface of your skin. This causes you to sweat in order to evaporate water and cool you.

However, when your body is exposed to cold temperatures, your blood vessels contract. In that case, your blood flow is reduced and your muscles may begin to tremble in order to generate heat.

Therefore, your temperature is regulated through three mechanisms:

  • Thermo-receptors. These are found in your skin and at the center of your hypothalamus.
  • Thermoregulatory effects. Sweating and increased blood flow.
  • Control from your brain.

How do you know if you have a fever?

Your body temperature is controlled by the hypothalamus and its other mechanisms, which balance the production of heat.

Your temperature is considered high when it exceeds 100ºF but you’ll also experience other symptoms. It can be urgent when it puts the patient’s life at risk.

Some of the signs that indicate that your body temperature is higher than it should be include the following:

  • The temperature measured in your mouth is higher than 100ºF.
  • In the rectum or ear, it’s higher than 101ºF.
  • Under your arm, the temperature is higher than 99ºF.

Do you want to know more? How to Reduce a Fever Naturally

Signs and symptoms

Fever is a symptom that can be accompanied by others, depending on its underlying cause. Many of them should be a reason for immediate medical consultation, as they can be a warning sign of more serious health problems. The most common ones include:

  • Vertigo.
  • Nausea.
  • Tachycardia.
  • Chills.
  • Sweating.
  • Muscle pain.
  • Lack of appetite.
  • A body temperature higher than 100ºF.
  • Increased respiratory frequence.

We should clarify that the mentioned symptoms don’t occur in the same way in all patients. In addition, they can occur due to different health problems. Therefore, your doctor needs to intervene and give an accurate diagnosis.

Risk factors

A sick woman on a couch.
  • Infection. This immune system response indicates that a foreign substance is attacking your body.
  • Medications. Antibiotics, narcotics, or antihistamines can cause a fever because these substances raise your body temperature.
  • Injuries. Suffering from some kind of trauma can trigger a fever. It can develop from a heart attack, stroke, burn, or heat stroke.
  • Other diseases can also raise the body temperature, such as arthritis, hyperthyroidism, and even cancer.

Meanwhile, a high temperature that’s lower than 100ºF could be due to milder causes like stress, hormonal fluctuations, too much exercise, or a high outdoor temperature.

Read also: Tips for Reducing Fever: Things to Keep in Mind

What’s hyperthermia?

This occurs when your body’s thermoregulators cannot keep up with the production of heat. Thus, your body temperature rises well above the normal range. When your temperature is higher than 104ºF, it’s considered hyperthermia.

Some of the main symptoms are:

  • Bleeding.
  • A dark color in your urine.
  • Muscle pain.
  • Fainting.
  • Disorientation.


  • A stroke.
  • Tumors.
  • Encephalitis.
  • Internal bleeding.
  • Neurosurgical complications.


When the patient doesn’t treat hyperthermia in time, it’s possible that the temperature will continue to increase. This can be dangerous, causing your thermoregulators to fail.
Thus, it’s essential to lower your body temperature immediately before you experience something like a seizure.


A doctor holding medications.

Overall, treatment must be instant. Aggressive cooling measures should be combined with hyperventilation using 100% oxygen.

  • Cool the skin with hypothermia blankets.
  • Immerse the patient in ice water.
  • Use fans.
  • Gastric lavage with saline solution.
  • If the above measures fail, hemodialysis can be performed to remove toxins from the bloodstream.


  • Avoid prolonged sun exposure, especially if you’ll be engaging in physical activity.
  • Wear sunscreen to protect your skin from burns, which slows the dissipation of heat.
  • In addition, be sure to drink at least two liters of water a day to stay hydrated.
  • If you’re exercising and you sense that your temperature is increasing, or you feel a sensation of humidity, stop immediately.
  • In addition, reduce your consumption of alcoholic beverages because they worsen dehydration.
  • During warm weather, wear light clothing and bright colors.
  • Don’t forget to ventilate your home and consume plenty of electrolytes.

We recommend: 7 reasons to drink cucumber juice

Finally, it’s very important that you understand the difference between a fever and hyperthermia. In addition to a very high body temperature, with hyperthermia, you aren’t able to reduce your temperature yourself.

Thus, waste no time in going to a doctor, especially in the case of children or the elderly.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.