Fever facts: A guide to symptoms, treatment, and when to see a doctor
- A fever is generally considered a body temperature over 100.4 degrees Fahrenheit, for children and adults.
- Fevers are commonly caused by viral or bacterial infections, as they are your body's natural defense to fight off pathogens and illness effectively.
- Most of the time, having a fever isn't a reason for major worry, and it should go away as you heal within several days — but there are other times where you should seek medical attention.
- This article was medically reviewed by Jason R. McKnight, MD, MS, a family medicine physician and clinical assistant professor at Texas A&M College of Medicine.
- Visit Insider's Health Reference library for more advice.
Although having a fever means your body temperature is above normal, it doesn't necessarily mean you have a serious illness like COVID-19.
There are many common conditions that can cause a fever, such as the flu or food poisoning. Even experiencing stress, having your period, or exercising can raise your body temperature.
So, if you're feeling feverish, don't panic. Here's what you need to know to determine the cause of your fever and treat it effectively.
What is considered a fever?
Though an exact normal body temperature can vary from person to person, it is generally considered to be 98.6°F. The following body temperatures are considered a fever:
As with normal body temperature, not everyone will experience low-grade or high fevers at exactly the same point. As a result, it's important to take into account your symptoms and always check in with a doctor if you feel concerned.
When you take your temperature, oral and rectal thermometers provide more accurate results than forehead or ear thermometers. For newborns or infants, rectal thermometers may be most effective, and for adults or children over 4 years old, an oral thermometer is the best bet.
You should wait 30 minutes after eating, drinking, or exercising before you take your temperature and at least six hours after taking medications that can lower your temperature, such as aspirin, Tylenol (acetaminophen), or Advil (ibuprofen).
Fever symptoms
However, you don't necessarily need to take your temperature to know you have a fever. You can monitor the following symptoms, which often accompany a fever:
You may also be able to feel if your forehead is hot or warm to the touch, although this is a more subjective measure.
"I find that using the back of my hand versus the palm is more sensitive, and it is easier for me to tell the difference in temperature," says Monique May, MD, a family physician based in Charlotte, NC.
If your forehead feels hot, and you are also experiencing several of the fever-related symptoms, it is likely that you do have a fever. However, if you do not have many of these symptoms, and you just feel slightly warm, it's more likely that it's due to physical exertion, wearing heavy clothing, or feeling stressed or excited.
What causes a fever?
A fever most commonly occurs when your body is fighting off a viral or bacterial infection. Your hypothalamus, the area of your brain that serves as your body's thermostat, reacts to an infection by raising your temperature.
"It's one of your body's ways of making you an inhospitable host for bacterial or viral infections," says internal medicine specialist Michelle N. Brooks, MD, an assistant professor and academic hospitalist at VCU Health.
The following are some of the illnesses that are often accompanied by a fever:
- Influenza
- Bronchitis
- Chickenpox
- Food poisoning
- Strep throat
- Measles
You can help determine what's causing your fever based on your symptoms. For example, coughing could indicate a respiratory infection, or pain when you urinate could indicate a urinary tract infection (UTI). Paying attention to these symptoms can help you localize what's causing the infection, Brooks says. It can also help you determine the difference between common conditions, like the flu, common cold, or allergies, and even COVID-19.
To help determine the cause of your fever, your doctor may listen for symptoms like wheezing, difficulty breathing, and whether you are thinking clearly or sound lethargic. And even though you might not be able to go to the doctor's office, you can still see a doctor through a virtual doctor's appointment.
"The best way is to have a video visit," May says. "That way the doctor can see how the patient looks and assess things like level of alertness or whether the person is pale."
During a telehealth or-in person visit, May says your doctor may ask you some of the following questions to figure out what's causing your fever:
- When did the fever start?
- What other symptoms are you having?
- Have you been exposed to any sick people at home, work, or school?
- Have you had any known exposure to COVID-19?
- Do you have any other medical conditions, like diabetes or cancer?
- Do you take any other medications, like steroids or immunosuppressants?
- Have you traveled recently?
- Have you been out of the country in the past three weeks?
How to break a fever
A fever will typically last from one to three days before going away on its own. In fact, it may be best not to bring down your fever so your body can continue to fight off the infection or virus that's causing it.
But if your fever makes you uncomfortable, there are medications and home remedies that may help lower your temperature and make you feel better.
Medications
Over-the-counter (OTC) as well as prescription medications are available that can help reduce your fever. Be sure to take these medications according to the label instructions or your doctor's recommendation.
These medications include:
- Tylenol or Anacin (acetaminophen). These OTC pain relievers help cool your body by triggering your hypothalamus, the area of your brain that serves as your body's thermostat, to lower your temperature.
- Advil or Motrin IB (ibuprofen). These OTC NSAIDs (nonsteroidal anti-inflammatory drugs) reduce your fever by blocking the enzyme that creates prostaglandins, the chemicals in your body that are causing your fever. "We usually recommend alternating acetaminophen and ibuprofen," Brooks says. People with liver or kidney problems may occasionally take acetaminophen and other NSAIDs, but should always consult with their doctor before taking any OTC pain reliever, as it could cause toxic hepatitis or reduced blood flow to the kidneys.
- Aspirin. This is an OTC NSAID that also reduces your fever by blocking the enzyme that creates prostaglandins. Never give aspirin to children or teenagers with a fever because it could trigger a rare but potentially fatal disorder called Reye's syndrome.
- Antibiotics. If the cause of your fever is a bacterial infection, such as strep throat or pneumonia, your doctor may prescribe an antibiotic to kill the infection.
- Antiviral drugs. If your fever is caused by a viral infection, such as influenza, your doctor may prescribe medication to destroy the virus.
Home remedies
The following home remedies may also help relieve your discomfort from a fever:
- Drink plenty of fluids. It's important to drink water, juices, or broth because a fever can cause you to become dehydrated. Children younger than a year old can be given Pedialyte, an oral rehydration solution.
- Take a sponge bath or bath with lukewarm water. This will help cool your body down if you have a fever. Don't use cold water, because it will make your body warm up. Don't leave your child unattended in the bathtub.
- Get plenty of rest. Being active can raise your body temperature, so it's important to get a lot of rest when you have a fever.
- Keep cool. Wear lightweight clothing and sleep with only a sheet or light blanket. Turn on a ceiling fan or portable fan to move the air and feel cooler.
When to see a doctor
If your fever persists for more than seven days, notify a doctor, May says. The same applies if you have to constantly take ibuprofen or acetaminophen to keep your fever down for more than three to five days.
Having a fever for longer than a week or having the symptoms below along with a fever may indicate a serious health problem, such as:
- Pneumonia
- Meningitis
- Skin or lymph system infection
- Kidney infection
- A malignant tumor
For infants
You should get medical help immediately if your baby is less than 3 months old and has a 100.4°F or higher fever.
You should also see a doctor if your older baby has a fever and shows symptoms of dehydration. These symptoms may include having a dry diaper for over eight hours, refusing to drink fluids, or crying without tears.
For children
If your child has a fever and shows any of these symptoms, you should take them to a doctor:
- Acting fussy or abnormally, even after taking medications to reduce their fever
- Signs of dehydration such as refusing to drink fluids or crying without tears
- Headache or stiff neck
- Abdominal pain
You should also see a doctor if your child's fever lasts for more than five consecutive days.
For adults
You should see your doctor if you have a fever and any of the following symptoms:
- Difficulty breathing
- Chest pain
- Severe headache
- Confusion
- Repeated vomiting
- A stiff neck or sensitivity to light, which are symptoms of meningitis, a serious inflammation of the fluids and membranes around your brain or spinal cord
- Skin rash
Takeaways
A fever is your body's natural way of helping you fight off an infection. Unless it's making you uncomfortable, you generally don't need to treat it. But if your fever persists for more than a week, your child's fever lasts longer than five days, or you have any of the above red-flag symptoms, you should see a doctor.
Once your temperature is back to normal on its own, without the need for medications to lower it, your illness will likely be gone. However, May says that if your fever may be due to a viral infection, to prevent infecting other people, you should wait 24 to 48 hours before returning to work, school, or close contact with others.
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