A normal temperature is about 98.6°F (37°C) when taken orally (in your child’s mouth) and 99.6°F (37.5°C) when taken rectally (in your child’s bottom). Many doctors define a fever as an oral temperature above 99.5°F (37.5°C) or a rectal temperature above 100.4°F (38°C).
You can get the most accurate temperature by taking his or her temperature rectally. But in a child older than 3 months of age, it’s fine to take it orally unless your doctor directs otherwise. Use a digital thermometer. Do not use a mercury thermometer. Mercury is an environmental toxin (poison), and you don't want to risk exposing your family to it.
If you're taking your child's temperature rectally, place him or her belly-down across your lap. Coat the tip of the thermometer with petroleum jelly (brand name: Vaseline) and insert it half an inch into the rectum. Stop if you feel any resistance. Hold the thermometer still and do not let go. When the thermometer beeps, remove it and check the digital reading.
If you're taking your child's temperature orally, place the end of the thermometer under his or her tongue, towards the back of the mouth. Have your child close his or her lips on the thermometer. Tell your child not to bite down or talk. When the thermometer beeps, remove it and check the digital reading.
If your child has any of the following warning signs, call your family doctor right away.
Younger than 3 months of age, call your doctor right away if your baby's rectal temperature is 100.4°F (38°C) or higher. Call your doctor even if your child doesn't seem sick. Babies this young can get very sick quickly.
Three months of age to 6 months of age, call your doctor if your baby has a temperature of 101°F (38.3°C) or higher, even if your baby doesn't seem sick.
Six months of age and older and has a fever of 102°F (38.8°C) to 102.9°F (39.4°C), watch how he or she acts. Call your doctor if the fever rises or lasts for more than 2 days.
Six months of age and older and has a fever of 103°F (39.4°C) or higher, call your doctor even if your child seems to feel fine.
Fevers are a sign that the body is fighting germs that cause infection. If your child is between 3 months of age and 3 years of age and has a low-grade fever (up to 100.2°F [37.8°C]), you may want to avoid giving him or her medicine. If your child is achy and fussy, and his or her temperature is above 100.2°F (37.8°C), you may want to give him or her some medicine.
If your baby is younger than 3 months of age and has a rectal temperature of 100.4°F (38°C) or higher, call the doctor or go to the emergency room right away. A fever can be a sign of a serious infection in young babies.
Do not give any medicine to babies who are younger than 2 months of age without talking to your doctor first.
Acetaminophen (one brand name: Children's or Infants' Tylenol) relieves pain and lowers fever. Check the package label or ask your doctor about the correct dosage for your child. The correct dosage depends on your child’s weight and age.
Ibuprofen is another medicine that can be used to lower a fever in children older than 6 months of age. Talk to your doctor before giving ibuprofen (two brand names: Children's Advil, Children's Motrin) to your child. Your doctor will tell you the correct dose for your child.
No. In rare cases, aspirin can cause Reye's syndrome in children. Reye's syndrome is a serious illness that can lead to death. Doctors recommend that parents should not give aspirin to children younger than 18 years of age.
Giving your child acetaminophen and a lukewarm bath may help lower his or her fever. Give the acetaminophen before the bath. If the bath is given without medicine, your child may start shivering as his or her body tries to raise its temperature again. This may make your child feel worse. Never use rubbing alcohol or cold water for baths.
Written by familydoctor.org editorial staff