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 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.

Fever temperatures

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 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, it is important 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 traveling in other countries need to be evaluated by your health professional.

Fever and respiratory symptoms are difficult 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 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 is 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 between the ages of 4 and 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 [80°F (27°C) to 90°F (32°C)] 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 70°F (21°C) or lower.

If you are unable 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 nonprescription 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 nonprescription 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 aspirin to anyone younger than age 20 unless your doctor tells you to.
  • Do not give your child naproxen sodium (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.
  • Fever lasts longer than 4 days.
  • Other symptoms develop, such as pain in one area of the body, a cough, or urinary symptoms.
  • Fever recurs more than once over 3 weeks.
  • Symptoms become more severe or frequent.

Prevention

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.

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 traveled 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 nonprescription 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

Organization

Centers for Disease Control and Prevention, Travelers' Health
1600 Clifton Road
Atlanta, GA  30333
Phone: 1-800-CDC-INFO (1-800-232-4636)
TDD: 1-888-232-6348
E-mail: cdcinfo@cdc.gov
Web Address: wwwn.cdc.gov/travel
 

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.


Credits

Author Jan Nissl, RN, BS
Editor Susan Van Houten, RN, BSN, MBA
Associate Editor Tracy Landauer
Primary Medical Reviewer H. Michael O'Connor, MD - Emergency Medicine
Primary Medical Reviewer William M. Green, MD - Emergency Medicine
Specialist Medical Reviewer Andrew Swan, MD, CCFP, FCFP - Family Medicine
Specialist Medical Reviewer Kathleen Romito, MD - Family Medicine
Last Updated September 2, 2009

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