A fever is a temporary increase in your body temperature, often due to an illness. Having a fever is a sign that something out of the ordinary is going on in your body.
For an adult, a fever may be uncomfortable, but usually isn't a cause for concern unless it reaches 103 F (39.4 C) or higher. For infants and toddlers, a slightly elevated temperature may indicate a serious infection.
Fevers generally go away within a few days. A number of over-the-counter medications lower a fever, but sometimes it's better left untreated. Fever seems to play a key role in helping your body fight off a number of infections.
You have a fever when your temperature rises above its normal range. What's normal for you may be a little higher or lower than the average normal temperature of 98.6 F (37 C).
Depending on what's causing your fever, additional fever signs and symptoms may include:
Children between the ages of 6 months and 5 years might experience febrile seizures. About a third of the children who have one febrile seizure will have another one, most commonly within the next 12 months.
To check your or your child's temperature, you can choose from several types of thermometers, including oral, rectal, ear (tympanic) and forehead (temporal artery) thermometers.
Although it's not the most accurate way to take a temperature, you can use an oral thermometer for an armpit (axillary) reading:
Use a rectal thermometer for infants:
Fevers by themselves may not be a cause for alarm — or a reason to call a doctor. Yet there are some circumstances when you should seek medical advice for your baby, your child or yourself.
An unexplained fever is greater cause for concern in infants and in children than in adults. Call your baby's doctor if your child is:
There's probably no cause for alarm if your child has a fever but is responsive — making eye contact with you and responding to your facial expressions and to your voice — and is drinking fluids and playing.
Call your child's doctor if your child:
Ask your child's doctor for guidance in special circumstances, such as a child with immune system problems or with a pre-existing illness.
Call your doctor if your temperature is 103 F (39.4 C) or higher. Seek immediate medical attention if any of these signs or symptoms accompanies a fever:
Fever occurs when an area in your brain called the hypothalamus (hi-poe-THAL-uh-muhs) — also known as your body's "thermostat" — shifts the set point of your normal body temperature upward. When this happens, you may feel chilled and add layers of clothing or wrap up in a blanket, or you may shiver to generate more body heat, eventually resulting in an elevated body temperature.
Normal body temperature varies throughout the day — it's lower in the morning and higher in the late afternoon and evening. Although most people consider 98.6 F (37 C) normal, your body temperature can vary by a degree or more — from about 97 F (36.1 C) to 99 F (37.2 C) — and still be considered normal.
Fever or elevated body temperature might be caused by:
Sometimes the cause of a fever can't be identified. If you have a fever for more than three weeks and your doctor isn't able to find the cause after extensive evaluation, the diagnosis may be fever of unknown origin.
Children between the ages of 6 months and 5 years may experience fever-induced convulsions (febrile seizures), which usually involve loss of consciousness and shaking of limbs on both sides of the body. Although alarming for parents, the vast majority of febrile seizures cause no lasting effects.
If a seizure occurs:
Most seizures stop on their own. Take your child to the doctor as soon as possible after the seizure to determine the cause of the fever.
Call for emergency medical assistance if a seizure lasts longer than five minutes.
You may be able to prevent fevers by reducing exposure to infectious diseases. Here are some tips that can help:
To evaluate a fever, your doctor may:
Because a fever can indicate a serious illness in a young infant, especially one 28 days or younger, your baby might be admitted to the hospital for testing and treatment.
For a low-grade fever, your doctor may not recommend treatment to lower your body temperature. These minor fevers may even be helpful in reducing the number of microbes causing your illness.
In the case of a high fever, or a low fever that's causing discomfort, your doctor may recommend an over-the-counter medication, such as acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin IB, others).
Use these medications according to the label instructions or as recommended by your doctor. Be careful to avoid taking too much. High doses or long-term use of acetaminophen or ibuprofen may cause liver or kidney damage, and acute overdoses can be fatal. If your child's fever remains high after a dose, don't give more medication; call your doctor instead.
Don't give aspirin to children, because it may trigger a rare, but potentially fatal, disorder known as Reye's syndrome.
Depending on the cause of your fever, your doctor may prescribe an antibiotic, especially if he or she suspects a bacterial infection, such as pneumonia or strep throat.
Antibiotics don't treat viral infections, but there are a few antiviral drugs used to treat certain viral infections. However, the best treatment for most minor illnesses caused by viruses is often rest and plenty of fluids.
For infants, especially those younger than 28 days, your baby might need to be admitted to the hospital for testing and treatment. In babies this young, a fever could indicate a serious infection that requires intravenous (IV) medications and round-the-clock monitoring.
You can try a number of things to make yourself or your child more comfortable during a fever:
Your appointment may be with your family doctor, general practitioner or pediatrician. Here's some information to help you get ready for your appointment and know what to expect from the doctor.
For a fever, some basic questions to ask your doctor include:
Don't hesitate to ask other questions during your appointment as they occur to you.
Be prepared to answer questions your doctor might ask you, such as: