Fever

Overview

A fever is a temporary rise in body temperature. It's one part of an overall response from the body's immune system. A fever is usually caused by an infection.

For most children and adults, a fever may be uncomfortable. But it usually isn't a cause for concern. For infants, however, even a low fever may mean there's a serious infection.

Fevers generally go away within a few days. A number of over-the-counter medications lower a fever. But you don't necessarily need to treat a fever if it's not causing discomfort.

Symptoms

Body temperatures vary slightly from person to person and at different times of day. The average temperature has traditionally been defined as 98.6 F (37 C). A temperature taken using a mouth thermometer (oral temperature) that's 100 F (37.8 C) or higher is generally considered to be a fever.

Depending on what's causing a fever, other fever signs and symptoms may include:

Sweating

Chills and shivering

Headache

Muscle aches

Loss of appetite

Irritability

Dehydration

General weakness

Taking a temperature

To take a temperature, you can choose from several types of thermometers, including oral, rectal, ear (tympanic) and forehead (temporal artery) thermometers.

Oral and rectal thermometers generally provide the most accurate measurement of core body temperature. Ear or forehead thermometers, although convenient, provide less accurate temperature measurements.

In infants, a rectal temperature, if doable, is somewhat more accurate. When reporting a temperature to your health care provider, give both the reading and the type of thermometer used.

Diagnosis

To evaluate a fever, your care provider may:

Ask questions about your symptoms and medical history

Perform a physical exam

Take nasal or throat samples to test for respiratory infections

Order tests, such as blood tests or a chest X-ray, as needed, based on your medical history and physical exam

Because a fever can indicate a serious illness in a young infant, especially two months of age or younger, your baby might be admitted to the hospital for testing and treatment.

Fever of unknown origin

When a fever lasts for more than three weeks — constantly or on several occasions — and there is no clear cause, it's usually called a fever of unknown origin. In these cases, you may need to see specialists in one or more medical fields for further evaluations and tests.

Treatment

For a low-grade fever, your care provider may not recommend taking medications to lower your body temperature. These minor fevers may be helpful in reducing the number of microbes causing your illness. Fevers above 102 F (38.9 C) tend to cause discomfort and often require treatment.

Over-the-counter medications

In the case of a high fever or a fever that causes discomfort, your care provider may recommend nonprescription medication, such as acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin IB, others).

Self care

You can try a number of things to make yourself or your child more comfortable during a fever:

Drink plenty of fluids. Drinking fluids will improve heat loss from the skin and replace water lost through sweating. Water and clear broth are healthy choices. Infants under 6 months should only have breast milk or formula.

Rest. You need rest to recover, and activity can raise your body temperature.

Stay cool. If you aren't shivering, dress in light clothing, keep the room temperature cool, and sleep with only a sheet or light blanket.

Preparing for your appointment

Your appointment may be with your family doctor, pediatrician or other care provider. Here's some information to help you get ready for your appointment and know what to expect from your care provider.

What you can do

Be aware of any pre-appointment restrictions. When you make the appointment, ask if there's anything you need to do in advance.

Write down information about the fever, such as when it started, how and where you measured it (orally or rectally, for example) and any other symptoms. Note whether you or your child has been around anyone who's been ill.

Write down key personal information, including possible exposure to anyone who's been ill or recent travel out of the country.

Make a list of all medications, vitamins and supplements that you or your child is taking.

Write down questions to ask the care provider.