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 the cause, fever signs and symptoms may include:
- Sweating
- Chills and shivering
- Headache
- Muscle aches
- Loss of appetite
- Irritability
- Dehydration
- General weakness
- Flushed complexion or hot skin.
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.
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.
Infants and toddlers
A fever is a particular cause for concern in infants and toddlers. Call your baby’s health care provider if your child is:
- Younger than 3 months old and has a rectal temperature of 100.4 F (38 C) or higher.
- Between 3 and 6 months old and has a rectal temperature higher than 102 F (38.9 C) or has a lower temperature but seems unusually irritable, sluggish or uncomfortable.
- Between 7 and 24 months old 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 runny nose, cough or diarrhea, you can call sooner.
Children
There’s probably no cause for alarm if your child has a fever but is responsive. This means your child makes eye contact with you and responds to your facial expressions and to your voice. Your child may also be drinking fluids and playing. Call your child’s health care provider if your child:
- Is listless, confused or has poor eye contact with you.
- Is irritable, vomits repeatedly, has a severe headache, sore throat, stomachache or other symptoms causing a lot of discomfort.
- Has a fever after being left in a hot car. Seek medical care immediately.
- Has a fever that lasts longer than three days.
- Has a seizure associated with the fever. Call 911 if the seizure lasts more than five minutes or your child doesn’t recover quickly.
Ask your child’s health care provider for guidance in special circumstances, such as a child with immune system problems or with a preexisting illness.
Adults
Seek immediate medical attention if any of these signs or symptoms accompanies a fever:
- Severe headache
- Rash
- Unusual sensitivity to bright light
- Stiff neck and pain when you bend your head forward
- Mental confusion, strange behavior or altered speech
- Persistent vomiting
- Difficulty breathing or chest pain
- Abdominal pain
- Pain when urinating
- Convulsions or seizures