A fever is usually a sign that something out of the ordinary is going on in your body. For an adult, a fever may be uncomfortable, but fever usually isn't dangerous unless it reaches 103 F (39.4 C) or higher. For very young children and infants, a slightly elevated temperature may indicate a serious infection.
But the degree of fever doesn't necessarily indicate the seriousness of the underlying condition. A minor illness may cause a high fever, and a more serious illness may cause a low fever.
Usually a fever goes 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:
Loss of appetite
High fevers between 103 F (39.4 C) and 106 F (41.1 C) may cause:
When to see a doctor
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.
Taking a temperature
To check your or your child's temperature, you can choose from several types of thermometers, including oral, rectal and ear (tympanic) thermometers.
Although it's not the most accurate way to take a temperature, you can use an oral thermometer for an armpit (axillary) reading:
Place the thermometer in the armpit and cross your arms or your child's arms over the chest.
Wait four to five minutes. The axillary temperature is slightly lower than an oral temperature.
If you call your doctor, report the actual number on the thermometer and where on the body you took the temperature.
Use a rectal thermometer for infants:
Place a dab of petroleum jelly on the bulb.
Lay your baby on his or her tummy.
Carefully insert the bulb one-half inch to one inch into your baby's rectum.
Hold the bulb and your baby still for three minutes.
Don't let go of the thermometer while it's inside your baby. If your baby squirms, the thermometer could go deeper and cause an injury.
An unexplained fever is greater cause for concern in infants and in children than in adults. Call your baby's doctor if your baby has a fever of 101 F (38.3 C) or higher. Also call your baby's doctor if your baby:
Has a fever and is younger than 3 months of age.
Refuses to eat or drink.
Has a fever and unexplained irritability, such as marked crying during a diaper change or when moved.
Has a fever and seems lethargic and unresponsive. In infants and children younger than age 2, these may be signs of meningitis — an infection and inflammation of the membranes and fluid surrounding the brain and spinal cord. If you're worried that your baby might have meningitis, take your baby to the doctor right away.
Is a newborn and has a lower than normal temperature — less than 97 F (36.1 C). Very young babies may not regulate their body temperature well when they are ill and may become cold rather than hot.
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:
Is listless or irritable, vomits repeatedly, has a severe headache or stomachache, or has any other symptoms causing significant discomfort.
Has a fever after being left in a hot car. Seek medical care immediately.
Has a fever that persists longer than a day (in children younger than age 2) or longer than three days (in children ages 2 and older).
Ask your child's doctor for guidance in special circumstances, such as a child with immune system problems or with a pre-existing illness. Your child's doctor also may recommend precautions if your child has just started taking a new prescription medicine.
Call your doctor if:
Your temperature is more than 103 F (39.4 C)
You've had a fever for more than three days
In addition, seek immediate medical attention if any of these signs or symptoms accompanies a fever:
Severe throat swelling
Unusual skin rash, especially if the rash rapidly worsens
Unusual sensitivity to bright light
Stiff neck and pain when you bend your head forward
Difficulty breathing or chest pain
Extreme listlessness or irritability
Abdominal pain or pain when urinating
Any other unexplained signs or symptoms
Your normal body temperature varies throughout the day — it's lower in the morning and higher in the late afternoon and evening. In fact, your normal temperature can range from about 97 F (36.1 C) to 99 F (37.2 C). Although most people consider 98.6 F (37 C) normal, your temperature may vary by a degree or more. Other factors, such as your menstrual cycle or heavy exercise, can affect your temperature.
A fever might be caused by:
A bacterial infection
Certain inflammatory conditions such as rheumatoid arthritis — inflammation of the lining of your joints (synovium)
A malignant tumor
Some medications, such as antibiotics and drugs used to treat high blood pressure or seizures
Some immunizations, such as the diphtheria, tetanus and acellular pertussis (DTaP) or pneumococcal vaccines
Sometimes it's not possible to identify the cause of a fever. If you have a temperature of 101 F (38.3 C) or higher 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.
Treatment & Drugs
With low-grade fever, doctors don't always recommend trying to lower the body temperature. Doing so may prolong the illness or mask symptoms and make it harder to determine the cause.
Some experts believe that aggressively treating a fever interferes with the body's immune response. Viruses that cause colds and other respiratory infections thrive at normal body temperature. By producing a low-grade fever, your body may be helping to eliminate a virus.
In the case of a high fever, your doctor may recommend an over-the-counter medication, such as:
Acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin, 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 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. For temperatures below 102 F (38.9 C), don't use fever-lowering drugs unless advised by your doctor.
Aspirin, for adults only. 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, such as stomach infection (gastroenteritis) and mononucleosis. There are a few antiviral drugs used to treat some specific viral infections. However, the best treatment for most viruses is often rest and plenty of fluids.
Lifestyle & Home Remedies
You can try a number of things to make yourself or your child more comfortable during a fever:
Drink plenty of fluids. Fever can cause fluid loss and dehydration, so drink water, juices or broth. For a child under age 1, use an oral rehydration solution such as Pedialyte. These solutions contain water and salts proportioned to replenish fluids and electrolytes. Pedialyte ice pops also are available.
Rest. It's necessary for recovery, and activity can raise your body temperature.
Stay cool. Dress in light clothing, keep the room temperature cool and sleep with only a sheet or light blanket.
Soak in lukewarm water. Especially for high temperatures, a lukewarm five- to 10-minute soak or a sponge bath can be cooling. If the bath causes shivering, stop the bath and dry off. Shivering raises the body's internal temperature — shaking muscles generate heat.