What Is Considered a Fever? (2023)


What is a fever?

A fever is when your body temperature rises higher than normal. A fever itself isn’t an illness. Rather, it’s a symptom of a wide range of health conditions. When your body temperature rises a few degrees above normal, it can be a sign that your immune system has been activated, often to fight an infection. It can also be a side effect of some medications and vaccinations.

What is considered a fever?

Common knowledge states that a “normal” body temperature is 98.6 degrees Fahrenheit (37 degrees Celsius). But your baseline body temperature may vary by a degree or more. It also fluctuates. It’s typically lower in the morning and higher in the evening. It’s higher during certain points of your menstrual cycle and when you’re exercising.

Infants and young children normally have slightly higher body temperatures than older children and adults. So infants and younger children have slightly higher fever temperatures.

There are no strict guidelines for what temperature is a fever, because body temperature varies by person, time of day and method of measurement. But healthcare providers most often say a fever temperature is 100.4 degrees F (38 degrees C) when measured orally (by mouth).

Rectal and ear thermometers typically measure temperatures at about 1.0 degrees F (0.6 degrees C) higher than oral thermometers. Skin thermometers (such as forehead thermometers) typically measure temperatures at about 1.0 degrees F (0.6 degrees C) lower than oral thermometers.

What is a low-grade fever?

A low-grade fever means a body temperature slightly above normal. This type of fever can be a sign your immune system has been mildly activated. There’s no standard low-grade fever range. But many healthcare providers consider a body temperature between 99.5 degrees F (37.5 degrees C) and 100.3 degrees F (38.3 degrees C) to be a low-grade fever.

(Video) What is a Fever? And the 98.6 degree myth.

What are fever symptoms?

In addition to an elevated temperature, you may experience the following symptoms:

  • Chills, feeling cold, shivering and shaking.
  • Body aches and headaches.
  • Fatigue (tiredness).
  • On and off or constant sweating.
  • Flushed complexion or hot skin.
  • Faster heart beats.

Additional fever symptoms in babies and children may include:

  • Lack of appetite — not eating and drinking well.
  • Earache or pulling at their ears.
  • High-pitched crying.
  • Fussiness.
  • Paleness or flushness.
  • Excessive thirst.
  • Decreased urination.

Possible Causes

What are the most common causes of fever?

A fever has many causes and can be a symptom of almost any illness. Common conditions that cause fever include:

  • Bacterial infections.
  • Viral infections such as influenza or COVID-19.
  • Gastrointestinal (GI) infections.
  • Urinary tract infections.
  • Skin infections.

You may also develop a fever due to:

  • A reaction to certain medications.
  • Vaccinations.
  • Autoimmune disorders.
  • Cancer.

Can allergies cause fever?

Allergies can cause cold-like symptoms such as sneezing, runny nose and watery eyes, but they typically don’t cause fever. Despite its name, hay fever (also called allergic rhinitis) doesn’t cause fever.

Care and Treatment

What’s the best way to measure body temperature?

You can take your temperature in several different parts of your body. The most common site is your mouth (oral temperature). Other sites include your ear (tympanic membrane), forehead (temporal artery) and armpit (axillary). The most accurate site is the rectum, and the least accurate site is the armpit.

The best way to measure your temperature is with a digital thermometer. Glass thermometers contain mercury and providers no longer recommend them.

How can I break a fever at home?

If your fever is mild — less than 101 degrees F (38.3 degrees C) — you usually don’t need treatment with medication. Make sure you drink plenty of fluids and get plenty of rest. Taking a lukewarm bath — about 98 degrees F (36.7 degrees C) — may also help bring your body’s temperature down. Keep an eye on signs of dehydration and other worsening symptoms.

If you’re feeling uncomfortable and your temperature is higher than 101 degrees F (38.3 degrees C), you can try to break the fever. The most common way to get rid of a fever is to use over-the-counter (OTC) medications such as acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs), including ibuprofen, naproxen and aspirin.

Don’t give aspirin to children under the age of 17. Aspirin in children may cause Reye’s syndrome, a sometimes fatal illness.

Does ibuprofen reduce fever?

Yes, you can take nonsteroidal anti-inflammatory drugs such as ibuprofen to try to reduce a fever.

How long does a fever last?

The cause of the fever determines how long it’ll last. Typically, if an infection is the cause of your fever, it should pass within three to four days. Call your healthcare provider if the fever lingers longer than that or comes along with breathing changes.

(Video) Fever in Kids: When to Call the Doctor

Can fevers be prevented?

You can prevent some fevers by avoiding the illnesses and infections that cause them. Sometimes, children develop fevers after receiving vaccinations. You can prevent these types of fevers by giving your child acetaminophen just before or after the vaccination. But you can’t prevent most fevers. They’re typically a sign that your body is doing what it’s supposed to do.

(Video) COVID-19 Fever Temperature - Penn State Health Coronavirus, Penn State Health

When to Call the Doctor

When should a fever be treated by a healthcare provider?

In adults, fevers less than 103 degrees F (39.4 degrees C) typically aren’t dangerous and aren’t a cause for concern. If your fever rises above that level, make a call to your healthcare provider for treatment.

In children, call your child’s healthcare provider if:

  • Their fever lasts more than five days.
  • Their fever is higher than 104 degrees F (40 degrees C).
  • Medications such as ibuprofen or acetaminophen don’t break the fever.
  • You’re concerned they aren’t behaving normally.
  • They have any problems breathing or urinating.

When should I go to the ER?

If you have a fever along with any of the following symptoms, go to your nearest emergency room or call 911. It may be a sign of a serious or life-threatening illness.

  • Pain or tenderness in your belly (abdomen).
  • Nausea or vomiting.
  • Severe headache.
  • Stiff neck.
  • Light irritates your eyes (photophobia).
  • Convulsions or seizures.
  • Difficulty breathing.
  • Strange behavior and/or altered speech.
  • Confusion or irritability.
  • Difficulty waking or extreme sleepiness.
  • Fever rash (small bleeding spots under your skin).

When should I take my child to the ER?

If your baby has a fever and is under 3 months of age, take them to the ER right away. Your baby’s immune system hasn’t developed fully yet, and they could have a serious infection.

If your child has a fever along with any of the following symptoms, call 911 or go to the nearest emergency room:

(Video) What Temperature is a Fever? What’s a Normal Body Temperature? Doctor Explains

  • Extreme sluggishness or drowsiness.
  • Lack of appetite.
  • Excessive drooling or difficulty swallowing.
  • Continuous crying.
  • Stiff neck.
  • Fever rash.
  • Difficulty breathing.
  • Severe abdominal pain.
  • Redness or swelling.
  • Dehydration (not drinking many fluids).
  • Decreased urination.

What are the possible complications or risks of not treating a fever?

Untreated fevers above 105.8 degrees F (41 degrees C) can be dangerous. If your body temperature reaches this level, your organs will begin to malfunction and will eventually fail.

Even moderate fevers can be dangerous for adults with lung or heart disorders because fever causes your breathing rate and heart rate to increase. Fever can also worsen the mental state of people with dementia.

Frequently Asked Questions

What is a recurrent fever?

A recurrent fever is a fever that keeps coming back multiple times over a period of time. Providers call these fevers episodic because they come and go. The fever lasts for a few days and then goes away for a stretch of time. Your child is healthy and acts normally between fevers. Recurrent fevers affect young children under the age of 5 most often. They’re one of the main symptoms of a collection of conditions called periodic fever syndromes.

What is a febrile seizure?

Some children have a side effect of fevers called febrile seizures. This happens in 2% to 4% of children under the age of 5. Some seizures cause jerking movements, or it may look like your child has passed out. When this happens, put your child on their side and don’t put anything in their mouth. Call 911 if the seizure lasts for more than five minutes and/or your child’s lips turn blue.

If the seizure lasts less than five minutes, notify their healthcare provider and get medical attention right away.

What is a fever dream?

Fever dreams are vivid, bizarre or unpleasant dreams you may experience when your body temperature rises higher than normal. Researchers don’t know the exact cause of fever dreams. But some scientists think fevers cause your brain to “overheat,” affecting your cognitive processing, which results in dreams stranger than your typical dreams. Fevers may also interrupt your REM sleep cycle, which can lead to unusual dreams.

(Video) At what temperature do you have a fever?

A note from Cleveland Clinic

While a fever can be uncomfortable, it’s typically a sign that your body is working properly and your immune system is kicking into action. You don’t need to treat low fevers, but you can take over-the-counter pain relievers until they pass. If you or your child has a higher temperature or your fever hasn’t passed within a few days, you should make a call to your healthcare provider. While infections most often cause fevers, there could be other underlying conditions you’ll want to get checked out.


Is a temperature of 100.0 a fever? ›

Despite the new research, doctors don't consider you to have a fever until your temperature is at or above 100.4 F. But you can be sick if it's lower than that.

Is 99 counted as fever? ›

An adult probably has a fever when the temperature is above 99°F to 99.5°F (37.2°C to 37.5°C), depending on the time of day.

Is a temperature of 101.1 bad? ›

Low-grade fever

The medical community generally defines a fever as a body temperature above 100.4 degrees Fahrenheit. A body temp between 100.4 and 102.2 degree is usually considered a low-grade fever. “If the temperature is not high, it doesn't necessarily need to be treated with medication,” Dr. Joseph said.

Is a 99.7 fever high? ›

Normal body temperature ranges from 97.5°F to 99.5°F (36.4°C to 37.4°C). It tends to be lower in the morning and higher in the evening. Most healthcare providers consider a fever to be 100.4°F (38°C) or higher. A person with a temperature of 99.6°F to 100.3°F has a low-grade fever.

Is a fever of 101.1 Covid? ›

If you're over 65 or immunocompromised — especially if you may have been exposed to COVID-19 — call your doctor if your fever reaches 101°. Anyone with a fever of 103° or higher should do the same. And if your temperature reaches 105°, go straight to an emergency room.

How high is Covid-19 fever? ›

Symptoms may appear 2-14 days after exposure to the virus. People with these symptoms or combinations of symptoms may have COVID-19: Fever greater than 99.9F or chills. Cough.

Why is 99.9 not a fever? ›

Although we think of normal body temperature as 98.6 degrees F, body temperature varies -- and so does the definition of fever. Since body temperature rarely climbs above 99.9 degrees without a reason, this guide will consider a fever to be present when the body temperature is 100.0 F (38 degrees C) or higher.

Can I go to work with a 99 fever? ›

All employees should stay home if they are sick until at least 24 hours after their fever* (temperature of 100 degrees Fahrenheit or 37.8 degrees Celsius or higher) is gone. Temperature should be measured without the use of fever-reducing medicines (medicines that contains ibuprofen or acetaminophen).

Why do I feel feverish but no fever? ›

It's possible to feel feverish but not be running an actual temperature. Underlying medical conditions, hormone fluctuations, and lifestyle may all contribute to these feelings. Feeling feverish or hot may be one of the first signs of having a fever. But sometimes you may feel like you have a fever when you do not.

Is 101 fever flu or COVID? ›

Fever: Coronavirus and flu both cause fever, but it's rare for the common cold. COVID-19 patients usually have a fever of 100 F or higher, while flu sufferers often experience fever of 100F to 102F that lasts three to four days. Headache: COVID-19 patients sometimes have headaches.

How long does COVID-19 fever usually last? ›

Many people with the disease run a low-grade fever for days, she said, and some may have no fever at all.

How do you break a fever? ›

You can break a fever by getting plenty of rest, drinking fluids, using blankets if you have shivers or an ice pack if you're too hot, and by taking medications like acetaminophen or ibuprofen.

What is a low-grade fever? ›

While body temperatures vary, most of us have an internal temperature around 98.6 degrees Fahrenheit. A temperature slightly higher than that is still normal. When your temperature is between 100.4 and 102.2, you have what is considered a low grade fever.

What does a low-grade fever feel like? ›

Some people may hardly notice that they have a low grade fever. However, others may experience various symptoms, including: feeling warm to the touch. sweating.

When is a fever an emergency? ›

Call your health care provider if your temperature is 103 F (39.4 C) or higher. Seek immediate medical attention if any of these signs or symptoms accompanies a fever: Severe headache. Rash.

Why do fevers spike at night? ›

Cortisol is higher during the day, and these higher levels suppress your immune activity to a large degree. When cortisol levels go down at night, your immune system is more active in fighting illness or infection. This is why fevers spike at night.

Should I cover myself with a blanket if I have a fever? ›

Dress light. Bundling up too much can make it harder to reduce a fever. If you have chills, try wearing a single, light layer and using one lightweight blanket. If your temperature's over 103ºF, let your doctor know.

What is the highest fever ever recorded? ›

115 degrees: On July 10, 1980, 52-year-old Willie Jones of Atlanta was admitted to the hospital with heatstroke and a temperature of 115 degrees Fahrenheit. He spent 24 days in the hospital and survived. Jones holds the Guinness Book of World Records honor for highest recorded body temperature.

What does a COVID headache feel like? ›

The research shows that covid-19 headaches are most similar to either tension headaches or migraines. The symptoms of tension-like headaches include: Moderate or severe pain. Pain on both sides of the head.

What is a COVID cough like? ›

A dry cough is one of the most common coronavirus symptoms, but some people may have a cough with phlegm (thick mucus). It can be difficult to control your cough but there are a few ways to help.

What is considered mild Covid? ›

Mild illness: Individuals who have any of the various signs and symptoms of COVID-19 (e.g., fever, cough, sore throat, malaise, headache, muscle pain, nausea, vomiting, diarrhea, loss of taste and smell) but do not have shortness of breath, dyspnea, or abnormal chest imaging.

Should I give Tylenol for 99.9 fever? ›

Treat Fever, if Necessary

No treatment is necessary for a mild fever unless the person is uncomfortable. If the fever is 102 or higher: Give an over-the-counter medicine such as acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) as directed on the label.

Should I go to work with a 99.9 fever? ›

You Have a Fever

“Use your judgment on how you're feeling, and try to limit exposure to others by good hand-washing.” However, if you have a fever with a temperature at or above 100 degrees Fahrenheit (37.8 degrees Celsius), Zeigler recommended staying home to avoid exposing others to whatever is making you sick.

Should I give Tylenol for 99.8 fever? ›

If the child is not acting bothered by the temperature, I usually tell my parents to hold off on giving acetaminophen or ibuprofen for a fever between 100.4 degrees and 102 degrees. However, if the child is acting lethargic, having pain or not wanting to drink fluids, I recommend giving medications.

How long are you contagious after a fever? ›

The flu is contagious for about 24 hours after your fever breaks. The Centers for Disease Control and Prevention advises staying home for at least 24 hours after your fever goes away without the help of ibuprofen (Motril or Advil) or acetaminophen (Tylenol).

Am I contagious if I don't have a fever? ›

While you may not see any symptoms, you may still be contagious. Understanding your infection and its contagious period will help you and others stay healthy.

How sick is too sick to work? ›

According to the Centers for Disease Control and Prevention (CDC), a fever is at least 100.4 degrees Fahrenheit or 38 degrees Celsius. If you have flu-like symptoms, the CDC recommends that you stay home for at least a day after your fever is gone, except to get medical attention or take care of necessities.

Why do you shiver with a fever? ›

Once the higher temperature is set, your body begins working to increase its temperature. You will feel cold because you are now at a lower temperature than your brain thinks you should be so your body will begin to shiver to generate heat and raise your temperature. This is the chills.

Do body aches mean fever? ›

Full-body aches often go hand-in-hand with a fever. As a higher body temperature causes you to shiver, your muscles tense up and may begin to ache. To regulate your body temperature, reach for fever-reducing pain medicine, take a cool bath and use only a thin blanket or sheet.

Why do I feel cold but my body is hot? ›

What Makes You Feel Colder When Your Body Is Hotter? It's actually a normal physiological response. As soon as your brain shifts its internal thermostat to a higher set point to fight off an infection, the rest of your body goes to work trying to generate extra heat to meet that higher temperature goal.

What are the 3 new Covid symptoms? ›

On June 30, the Centers for Disease Control and Prevention added three symptoms to its COVID-19 list: Congestion/stuffy nose, nausea and diarrhea. Those three new conditions now join other symptoms identified by the CDC: Fever.

When is COVID most contagious? ›

You are most infectious (or contagious) in the first 5 days after your symptoms start. You can also spread COVID-19 in the 48 hours before your symptoms start. If you never have symptoms, consider yourself most infectious in the 5 days after you test positive.

Does Covid start suddenly or gradually? ›

The first symptoms of COVID-19 can be more gradual. While COVID-19 symptoms can develop as early as two days after you're infected, the Centers for Disease Control and Prevention (CDC) says five days after infection is typical.

What does COVID fatigue feel like? ›

It can make you feel dull and tired, take away your energy, and eat away at your ability to get things done. Depending on the seriousness of your COVID-19 infection, it may last 2 to 3 weeks. But for some people with a severe infection, the brain fog-like fatigue and pain can linger for weeks or months.

When does Covid fever start? ›

Symptoms may appear 2-14 days after exposure to the virus. Anyone can have mild to severe symptoms. Possible symptoms include: Fever or chills.

What does COVID sore throat feel like? ›

Because COVID-19 is an illness caused by a virus, a COVID-19 sore throat may look and feel like other viral sore throats. One clue that you have viral pharyngitis is that it is often accompanied by other common symptoms.

Is it OK to sleep under fan during fever? ›

Treating Your Child's Fever

The room should be comfortable, not too hot or too cool. If the room is hot or stuffy, a fan may help.

Is it OK to bundle up with a fever? ›

While having a fever can give you chills, it's important not to bundle up or lie under heavy blankets as this can raise your internal temperature. Instead, dress in light clothing and sleep with a sheet to keep from overheating.

Can being tired raise your temperature? ›

A lack of sleep can cause a fever by increasing the skin temperature, the temperature of the brain, as well as increasing the susceptibility to infections. However, due to several conditions like an overactive thyroid, arthritis, and pneumonia, sleep deprivation and fever can occur simultaneously.

Can you tell if you have a low-grade fever? ›

Signs and Symptoms of Low-Grade Fever

Warm skin. A flushed face. Glassy eyes. Chills or Shivering.

What not to do when you have a fever? ›

What NOT to do
  1. Bundle up or cover up with a blanket. ...
  2. Starve as it will leave a person with no energy to fight off the infections and make the person feel weak.
  3. Always pop an antibiotic as it might not work every time. ...
  4. Self-medicate because you may not need medicines to bring down a fever.
Jul 15, 2018

How do I know if my fever is viral or bacterial? ›

Bacterial Infections
  1. Symptoms persist longer than the expected 10-14 days a virus tends to last.
  2. Fever is higher than one might typically expect from a virus.
  3. Fever gets worse a few days into the illness rather than improving.
Nov 21, 2019

When you have a fever should you stay warm or cold? ›

Warming up, but not bundling up: Wrapping yourself in an extra blanket or two to keep from shivering when you have a fever is fine—just don't overdo it. Once you get comfortable, take the covers off to avoid overheating. Wear clothes that are appropriate for the weather rather than layering.

What fever is too high for COVID? ›

If you're over 65 or immunocompromised — especially if you may have been exposed to COVID-19 — call your doctor if your fever reaches 101°. Anyone with a fever of 103° or higher should do the same. And if your temperature reaches 105°, go straight to an emergency room.

At what temperature should I call an ambulance? ›

Once a fever goes beyond the high level, an adult enters dangerous fever levels (104 F – 107 F). This dangerous level, also known as hyperpyrexia, is considered a medical emergency and you should seek medical care immediately.

Why do I feel cold and shaking without a fever? ›

You may experience chills without fever due to exposure to cold temperatures, intense exercise, or certain health conditions. Treatment depends on the underlying cause. Chills (shivering) are caused by rapid alternation between muscle contractions and relaxation.

Is 100 a safe temperature? ›

The average normal body temperature is generally accepted as 98.6°F (37°C). Some studies have shown that the "normal" body temperature can have a wide range, from 97°F (36.1°C) to 99°F (37.2°C). A temperature over 100.4°F (38°C) most often means you have a fever caused by an infection or illness.

Should I go to work with a fever of 100? ›

All employees should stay home if they are sick until at least 24 hours after their fever* (temperature of 100 degrees Fahrenheit or 37.8 degrees Celsius or higher) is gone. Temperature should be measured without the use of fever-reducing medicines (medicines that contains ibuprofen or acetaminophen).

How fever is defined in Covid 19? ›

Only 10 (19%) publications specified the minimum temperature used to define a fever with values that varied from a 37.3 °C (99.1 °F) to 38.1 °C (100.6 °F). Conclusions: There is a disturbing lack of precision in defining fever in COVID-19 publications.

Can you survive 110 degree fever? ›

Mild or moderate states of fever (up to 105 °F [40.55 °C]) cause weakness or exhaustion but are not in themselves a serious threat to health. More serious fevers, in which body temperature rises to 108 °F (42.22 °C) or more, can result in convulsions and death.

What do I do if I have a fever of 100? ›

To treat a fever at home:
  1. Drink plenty of fluids to stay hydrated.
  2. Dress in lightweight clothing.
  3. Use a light blanket if you feel chilled, until the chills end.
  4. Take acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin IB, others). Follow the directions on the label.

Is 100 degrees too hot for a human? ›

The wet-bulb temperature that marks the upper limit of what the human body can handle is 95 degrees Fahrenheit (35 Celsius). But any temperatures above 86 degrees Fahrenheit (30 Celsius) can be dangerous and deadly.

Can you get COVID-19 a fever? ›

Symptoms may appear 2-14 days after exposure to the virus. Anyone can have mild to severe symptoms. Possible symptoms include: Fever or chills.

Can you have COVID-19 run a fever? ›

Fever seems to be one of the more common early markers of COVID-19, Kline noted. But you shouldn't necessarily expect a high-grade fever with dangerously elevated temperatures. Many people with the disease run a low-grade fever for days, she said, and some may have no fever at all.

What is the danger zone for a fever? ›

Adults. Call your health care provider if your temperature is 103 F (39.4 C) or higher. Seek immediate medical attention if any of these signs or symptoms accompanies a fever: Severe headache.

What temp is alarming for Covid? ›

Fever is a common symptom of COVID-19. A body temperature of 100.4 degrees F or higher is generally seen in people with COVID-19, although some people may feel as though they have fever even though their temperature readings are normal.

Can a fever mean nothing? ›

A fever can mean a lot of different things, but most low-grade and mild fevers are nothing to worry about. Most often, an increase in body temperature is a normal response to an infection, like a cold or the flu.


1. VERIFY | What body temperature is considered a fever?
2. Research Finds New Normal When It Comes To Average Body Temperature
(CBS New York)
3. I have High Grade Fever, what should I do? - Dr. Brij Mohan Makkar
(Doctors' Circle World's Largest Health Platform)
4. What is a Low Grade Fever? | Vicks
5. The problem with tracking fevers during coronavirus
(Verge Science)
6. What Is A Normal Body Temperature: What Temperature Is Considered A Fever?


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