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:

  • Sweating
  • Shivering
  • Headache
  • Muscle aches
  • Loss of appetite
  • Dehydration
  • General weakness

High fevers between 103 F (39.4 C) and 106 F (41.1 C) may cause:

  • Hallucinations
  • Confusion
  • Irritability
  • Convulsions
  • Dehydration

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, 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 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.

Infants

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:

  • Younger than age 3 months and has a rectal temperature of 100.4 F (38 C) or higher.
  • Between ages 3 to 6 months and has a 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 to 24 months and has a 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.
  • A newborn and has a lower than normal temperature — less than 97 F (36.1 C). Very young babies may not regulate body temperature well when they're ill and may become cold rather than hot.

When in doubt, go ahead and call your child's doctor, whether you think your baby's temperature is abnormally high or abnormally low.

Children

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 (in children age 2 and older).
  • 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. Your child's doctor may also recommend precautions if your child has just started taking a new prescription medicine.

Adults

Call your doctor if:

  • Your temperature is 103 F (39.4 C) or higher
  • 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 headache
  • 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
  • Mental confusion
  • Persistent vomiting
  • Difficulty breathing or chest pain
  • Extreme listlessness or irritability
  • Abdominal pain or pain when urinating
  • Muscle weakness or sensory changes, which might indicate a problem with your nerves, spinal cord or brain function (focal neurologic deficit)
  • Seizure
  • Any other unexplained signs or symptoms
May. 29, 2014

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