Fever is the body's normal and healthy
reaction to infection and other illnesses, both minor and serious. It helps the
body fight infection. Fever is a symptom, not a disease. In most cases, having
a fever means you have a minor illness. When you have a fever, your other
symptoms will help you determine how serious your illness is.
Temperatures in this topic are oral temperatures. Oral
temperatures are usually taken in older children and adults.
Most people have an average
body temperature of about
98.6°F (37°C), measured orally
(a thermometer is placed under the tongue). Your temperature may be as low as
97.4°F (36.3°C) in the morning
or as high as 99.6°F (37.6°C)
in the late afternoon. Your temperature may go up when you exercise, wear too
many clothes, take a hot bath, or are exposed to hot weather.
A fever is a high body
temperature. A temperature of up to
102°F (38.9°C) can be helpful
because it helps the body fight infection. Most healthy children and adults can
tolerate a fever as high as
103°F (39.4°C) to
104°F (40°C) for short periods
of time without problems. Children tend to have higher fevers than
The degree of fever may not show how serious the
illness is. With a minor illness, such as a cold, you may have a temperature,
while a very serious infection may cause little or no fever. It is important to
look for and evaluate other symptoms along with the fever.
are not able to measure your temperature with a thermometer, you need to
look for other symptoms of illness. A fever without other symptoms that lasts 3
to 4 days, comes and goes, and gradually reduces over time is usually not a
cause for concern. When you have a fever, you may feel tired, lack energy, and
not eat as much as usual. High fevers are not comfortable, but they rarely
cause serious problems.
Oral temperature taken after smoking or
drinking a hot fluid may give you a false high temperature reading. After
drinking or eating cold foods or fluids, an oral temperature may be falsely
low. For information on how to take an
accurate temperature, see the topic
Viral infections, such as colds and
bacterial infections, such as a
urinary tract infection or
pneumonia, often cause a fever.
outside your native country can expose you to other diseases. Fevers that begin
after travel in other countries need to be evaluated by your doctor.
Fever and respiratory symptoms are hard to
evaluate during the flu season. A fever of
102°F (38.9°C) or higher for 3
to 4 days is common with the flu. For more information, see the topic
Respiratory Problems, Age 12 and Older.
Recurrent fevers are those that occur 3 or more times within 6 months and
are at least 7 days apart. Each new viral infection may cause a fever. It may
seem that a fever is ongoing, but if 48 hours pass between fevers, then the
fever is recurring. If you have frequent or recurrent fevers, it may be a
symptom of a more serious problem. Talk to your doctor about your
In most cases, the illness that
caused the fever will clear up in a few days. You usually can treat the fever
at home if you are in good health and do not have any medical problems or
significant symptoms with the fever. Make sure that you are taking enough foods
and fluids and urinating in normal amounts.
Check your symptoms to decide if and when
you should see a doctor.
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It's easy to become dehydrated when you have a fever.
In the early stages, you may be
able to correct
mild to moderate dehydration with home treatment
measures. It is important to control fluid losses and replace lost
If you become
mildly to moderately dehydrated while working outside or exercising:
Rest and take it easy for 24 hours, and continue to drink a
lot of fluids. Although you will probably start feeling better within just a
few hours, it may take as long as a day and a half to completely replace the
fluid that you lost.
Many people find that taking a lukewarm [80°F (27°C) to
shower or bath makes
them feel better when they have a fever. Do not try to take a shower if you are
dizzy or unsteady on your feet. Increase the water temperature if you start to
shiver. Shivering is a sign that your body is trying to raise its temperature.
Do not use rubbing alcohol, ice, or cold water to cool
Dress lightly when you have a fever. This will help
your body cool down. Wear light pajamas or a light undershirt. Do not wear very
warm clothing or use heavy bed covers. Keep room temperature at
If you are not able to measure your temperature, you
need to look for other symptoms of illness every hour while you have a fever
and follow home treatment measures.
Talk to your child's doctor before switching back and
forth between doses of acetaminophen and ibuprofen. When you switch between two
medicines, there is a chance your child will get too much medicine.
Be sure to check your temperature every 2 to 4 hours to make
sure home treatment is working.
Call your doctor if any of the following occur during home
The best way to prevent fevers is to reduce
your exposure to infectious diseases.
Hand-washing is the single most important prevention
measure for people of all ages.
Immunizations can reduce the risk for fever-related illnesses, such as the flu. Although no vaccine is 100% effective, most routine immunizations are effective for 85% to 95% of the people who receive them. For more information, see the topic Immunizations.
To prepare for your appointment, see the topic Making the Most of Your Appointment.
You can help your
doctor diagnose and treat your condition by being prepared to
answer the following questions:
The CDC's Travelers' Health Web site provides health
information for the traveler. The Web site provides information on
immunizations that are needed for travel to various areas of the world. It also
provides information for safe travel, including traveling with children and
with people who have special needs. Information about current outbreaks of
disease in the world is also provided. The CDC is the leading federal agency
for protecting U.S. citizens' health and safety by providing credible health
information and health promotion.
September 13, 2012
William H. Blahd, Jr., MD, FACEP - Emergency Medicine & H. Michael O'Connor, MD - Emergency Medicine
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