Fever in Teens and Adults

Most people have an average body temperature of about 98.6°F (37°C), measured orally (under the tongue). Your temperature may be as low as 97.4°F (36°C) in the morning or as high as 99.6°F (38°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 (39°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°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 show how serious the illness is. With a minor illness, such as a cold, you may have a fever. But a very serious infection may cause little or no fever. It's important to look for and evaluate other symptoms along with the fever.

If you can't 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 usually isn't a cause for concern. When you have a fever, you may feel tired, lack energy, and not eat as much as usual. High fevers aren't comfortable. But they rarely cause serious problems.

An oral temperature taken after you smoke or you drink a hot fluid may give you a false high temperature reading. After you drink or eat cold foods or fluids, your oral temperature may be falsely low.

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 start after travel in other countries need to be checked by your doctor.

Fever and respiratory symptoms are hard to evaluate during the flu season. A fever of 102°F (39°C) or higher for 3 to 4 days is common with the flu.

Recurrent fevers are ones 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, they may be a symptom of a more serious problem. Talk to your doctor about your fevers.

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 don't 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.

If a low body temperature is your only symptom, it's not something to worry about. If a low body temperature occurs with other symptoms, such as chills, shaking, breathing problems, or confusion, then this may be a sign of more serious illness.

Low body temperature may occur from cold exposure, shock, alcohol or drug use, or certain metabolic disorders, such as diabetes or hypothyroidism. A low body temperature may also occur with an infection. This is most likely in newborns, older adults, and people who are frail. An overwhelming infection, such as sepsis, may also cause an abnormally low body temperature.

Ask your doctor if you can take an over-the-counter pain medicine, such as acetaminophen (Tylenol), ibuprofen (Advil, Motrin), or naproxen (Aleve). Be safe with medicines. Read and follow all instructions on the label.

To prevent dehydration, drink plenty of fluids. Choose water and other clear liquids until you feel better. If you have kidney, heart, or liver disease and have to limit fluids, talk with your doctor before you increase the amount of fluids you drink.

Call your doctor now or seek immediate medical care if:

• You have a fever of 104°F or higher.
• You have a fever that stays high.
• You have a fever and feel confused or often feel dizzy.
• You have trouble breathing.
• You have a fever with a stiff neck or a severe headache.

Watch closely for changes in your health, and be sure to contact your doctor if:

• You have any problems with your medicine, or you get a fever after starting a new medicine.
• You do not get better as expected.