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:
Chills and shivering
Loss of appetite
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.
Taking a temperature
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:
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 1/2 to 1 inch (1.3 to 2.5 centimeters) 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.
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.
Unexplained fever is a greater cause for concern in infants and in children than in adults. Call your baby’s doctor if your child is:
Younger than age 3 months and has a rectal temperature of 100.4 F (38 C) or higher.
Between ages 3 and 6 months and has a rectal temperature up to 102 F (38.9 C) and seems unusually irritable, lethargic or uncomfortable or has a temperature higher than 102 F (38.9 C).
Between ages 6 and 24 months and has a rectal temperature higher than 102 F (38.9 C) that lasts longer than one day but shows no other symptoms. If your child also has other signs and symptoms, such as a cold, cough or diarrhea, you might call your child’s doctor sooner based on severity.
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 lasts longer than three days.
Appears listless and has poor eye contact with you.
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:
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
Abdominal pain or pain when urinating
Convulsions or seizures