When Is a Fever Too High?

And what should you do about it?

High-grade fevers, called hyperpyrexia, involve temperatures above 103 degrees and can be dangerous. However, when determining if a fever is a risk to yourself or your child, it's more complicated than just looking at the number—especially in children.

For most people, most of the time, a fever isn't dangerous enough to cause brain damage. This may go against what you've been taught.

It helps to know what causes a fever, what the potential complications can be, and when to call your healthcare provider or head to the emergency room. It's also important to know what's different about fevers in kids versus adults.

This article will discuss fevers and how you know when one is too high. It will also talk about what you should do if you have a low or high fever.

Why You Get Fevers

Usually, fevers are a good thing. They're one of the ways your body naturally fights off infections.

A part of the brain called the hypothalamus acts as a thermostat for your body. Most of the time, it keeps body temperatures around 98.6 degrees. When you get sick, though, the hypothalamus raises the temperature to make it hard for germs to live and multiply in the body.

It's great when a fever fights against the germs in your body. But it's not so great when the fever gets so high that it could harm you.

Causes of a Fever

A lot of things can cause high fevers. Some of the causes typically begin with low-grade fevers that can turn into high-grade ones, such as:

  • Viruses
  • Bacteria
  • Fungi
  • Toxins
  • Drugs

If you don't receive treatment for your fever or your body doesn't respond to treatment, the fever can become dangerous.

Causes of Fevers

Verywell / Jiaqi Zhou

Some medical conditions are associated with high-grade fever. These medical conditions include:

Symptoms and Complications of a Fever

As your fever rises, it may cause new symptoms.

Low-grade fever (pyrexia) symptoms include:

Early high-grade fever (hyperpyrexia) symptoms may still include those from the list above, plus:

Persistent or worsening high-grade fever can also cause:

  • Contracted (small) pupils
  • Mild confusion
  • Cool, moist, pale skin
  • Upset stomach or vomiting
  • Decreased urine or inability to urinate

Longer-lasting high-grade fever or temperatures above 106.1 F can lead to:

Adults who have fevers over 105 degrees need medical attention to prevent serious, long-term consequences.

Brain Damage and Death

While high fevers, especially those that last a long time, can lead to brain damage and death, this is extremely rare. Brain damage can occur if a fever goes above 107.6.

According to a 2016 study, heatstroke is the most deadly heat-related illness. It kills 58% or more of the people it affects. Among survivors, most make full recoveries. But some may have long-term organ damage.

Organs that can be damaged by a prolonged high fever include:

  • Brain
  • Heart and cardiovascular system
  • Kidneys
  • Liver
  • Intestines

Proper treatment is the key to preventing severe complications of high-grade fevers.

Treatment of a Fever

If someone has a fever but feels fine for the most part, treatment isn't necessary. In fact, because the fever's job is to help kill an infection, treating a low-grade fever can interfere with the body's efforts to fight germs.

When it comes to children who have a fever, a rule of thumb is that if they're playing and have energy, there's no immediate danger.

When fever-related symptoms are making you feel lousy or the temperature has crept up near that 103–104 degree mark, an over-the-counter fever-reducing medication like Tylenol (acetaminophen) or Motrin/Advil (ibuprofen) can help you feel better.

These medications provide only temporary results. They work for four to eight hours and then wear off. This means your fever may come back, and you'll need to take more. This doesn't mean something is wrong or that it didn't work.

Children and teenagers should not be given aspirin for a fever. They run the risk of getting Reye's syndrome, a rare and serious illness that causes brain and liver damage.

Rest and plenty of liquids can help your body fight against the fever and underlying illness as well.

Other home remedies may help, but you need to know which ones are safe and effective. You also need to know which ones are potentially harmful. Talk to your healthcare provider to learn which home remedies are best.

Treatment by Temperature

For most adults and older children, looking at the symptoms more than the number on the thermometer can help you determine if there's a serious health issue. Still, it's good to keep an eye on how high the fever gets.

Adults and Children 4+
Temperatures Degrees in Fahrenheit
High-Grade 103
Potentially Dangerous 104
Get Medical Attention 105 and up

With children under 3 years of age, and especially with babies, it pays to be more cautious and know what the exact temperature is.

Fever in very young children can be a sign that something is seriously wrong, so it shouldn't be ignored. Your pediatrician should have an on-call number so you can get advice at any time. In some cases, you may want to go straight to the emergency room.

Babies and Toddlers
Temperatures by Age Degrees in Fahrenheit What to Do
0-3 Months 100 oral, 100.4 rectal Call healthcare provider or go to ER
3 Months-3 Years 102.2 Call healthcare provider for advice, even after hours

Medical Care

If your fever is caused by an infection, it won't go away until the infection is gone or at least improves. Depending on the type of sickness, this may require medical treatment.

If your fever doesn't go away or you have additional symptoms that show you have an illness, you should see a healthcare provider.

If you go to your healthcare provider's office, urgent care, or the ER for fever treatment, you can expect medications and testing to figure out what's causing the elevated temperature.

Summary

A fever is one way your body naturally fights against infections. High fevers are 103 degrees or above. A potentially dangerous fever begins when your temperature is at least 104 degrees. If you have a fever that is 105 degrees or higher, you need immediate medical attention.

A Word From Verywell

Adults are usually able to determine when our symptoms are making us feel so bad that we need to seek medical treatment. But if you aren't sure, learn how to check your cold and flu symptoms, evaluate a fever, and know the situations when you should see a healthcare provider for a fever.

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4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Seattle Children's Hospital. Fever - myths versus facts. Published March 11, 2021.

  2. Cleveland Clinic. Fever: Symptoms, causes, care & treatment.

  3. MedlinePlus. Fever.

  4. Walter EJ, Hanna-Jumma S, Carraretto M, Forni L. The pathophysiological basis and consequences of fever. Crit Care. 2016 Jul 14;20(1):200. doi:10.1186/s13054-016-1375-5

Additional Reading
  • KidsHealth. Fevers. Published September 2018.