Fever, Age 12 and Older

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Fever, Age 12 and Older

Topic Overview

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.

Normal body temperature

Most people have an average body temperature of about 37°C (98.6°F), measured orally (a thermometer is placed under the tongue). Your temperature may be as low as 36.3°C (97.4°F) in the morning or as high as 37.6°C (99.6°F) 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.

Fever temperatures

A fever is a high body temperature. A temperature of up to 38.9°C (102°F) can be helpful because it helps the body fight infection. Most healthy children and adults can tolerate a fever as high as 39.4°C (103°F) to 40°C (104°F) for short periods of time without problems. Children tend to have higher fevers than adults.

The degree of fever may not indicate 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.

If you 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 may 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 Body Temperature.

Causes of fever

Viral infections, such as colds and flu, and bacterial infections, such as a urinary tract infection or pneumonia, often cause a fever.

Travel outside your native country can expose you to other diseases. Fevers that begin after travelling 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 38.9°C (102°F) 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 fevers.

Treating a fever

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.

Use the Check Your Symptoms section to decide if and when you should see a doctor.

Check Your Symptoms

Home Treatment

It's easy to become dehydrated when you have a fever. Watch for early signs of dehydration and drink extra fluids, especially water. Adults should drink at least 10 glasses of liquid a day to replenish lost fluids. Children ages 4 to 10 should drink at least 6 to 10 glasses. You may feel better if you eat light, easily digested foods, such as soup.

Many people find that taking a lukewarm [27°C (80°F) to 32°C (90°F)] 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 your body.

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 21°C (70°F) or lower.

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.

Medicine you can buy without a prescription
Try a non-prescription medicine to help treat your fever or pain:

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.

Safety tips
Be sure to follow these safety tips when you use a non-prescription medicine:
  • Carefully read and follow all directions on the medicine bottle and box.
  • Do not take more than the recommended dose.
  • Do not take a medicine if you have had an allergic reaction to it in the past.
  • If you have been told to avoid a medicine, call your doctor before you take it.
  • If you are or could be pregnant, do not take any medicine other than acetaminophen unless your doctor has told you to.
  • Do not give ASA to anyone younger than age 20 unless your doctor tells you to.
  • Do not give your child naproxen (such as Aleve) to children younger than age 12 unless your child's doctor tells you to.

Be sure to check your temperature every 2 to 4 hours to make sure home treatment is working.

Symptoms to Watch For During Home Treatment

Use the Check Your Symptoms section to evaluate your symptoms if any of the following occur during home treatment:

  • Level of consciousness changes.
  • You have signs of dehydration and you are unable to drink enough to replace lost fluids.
  • Other symptoms develop, such as pain in one area of the body, a cough, or urinary symptoms.
  • Symptoms become more severe or frequent.

Prevention

The best way to prevent fevers is to reduce your exposure to infectious diseases. Handwashing 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.

Preparing For Your Appointment

To prepare for your appointment, see the topic Making the Most of Your Appointment.

You can help your health professional diagnose and treat your condition by being prepared to answer the following questions:

  • What is the history of your fever?
    • When did you fever start?
    • How often do you have a fever?
    • How long does your fever last?
    • Does your fever have a pattern?
    • Are you able to measure your temperature? How high is your fever?
  • Have you had any other health problems over the past 3 months?
  • Have you recently been exposed to anyone who has a fever?
  • Have you recently travelled outside the country or been exposed to immigrants or other nonnative people?
  • Have you had any insect bites in the past 6 weeks, including tick bites?
  • What home treatment measures you have tried? Did they help?
  • What non-prescription medicines have you taken? Did they help? Keep a fever chart of what your temperature was before and after home treatment.
  • Do you have any health risks?

Other Places To Get Help

Online Resource

Traveler's Health: National Center for Infectious Disease
Centers for Disease Control and Prevention
Web Address: www.cdc.gov/travel
 

This 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 people with special needs. Information about current outbreaks of disease in the world is also provided.


Credits

By Healthwise Staff
Primary Medical Reviewer William H. Blahd, Jr., MD, FACEP - Emergency Medicine
Specialist Medical Reviewer H. Michael O'Connor, MD - Emergency Medicine
Last Revised June 13, 2011

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.