Fever in Children From Birth to 3 Years Old

What is a fever?
Fever is a common symptom of illness.  We define a fever as a temperature of 100.5 F (38 C) or higher.  The height of a fever does not determine the cause of the illness but can be an important clue. Fever is just one indicator of how a child is doing, and we always encourage parents to look at the overall behavior of their child considering such things as fussiness, clinging, work of breathing, interest in feeding, consolability etc.  If you child is ill and you are worried, we want to hear from you or see you in person.

How do I take my child’s temperature?
In general we encourage at home use of digital thermometers and using an armpit or oral temperature. Rectal temperatures are more accurate but more difficult to take.  Rectal temperatures are a bit easier with infants and the precise temperature is more important with infants. Temperature taken in the armpit is usually 1 degree lower than an oral temperature. We will use a temperature obtained in our office for clinical decision making about how much testing is needed to diagnose a cause, and will rely on home temperatures and parental perception of severity of illness to guide us on whether or not an appointment is needed.

Do I need to bring my child to the office?
Any infant less than 3 months of age with a fever should be evaluated in our office.

Infants aged 3 months to 3 years with a fever who appear ill or are not feeding well should be seen, and even if appearing well should be seen in our office if their fever lasts more than 3 days or is over 102 F (38.9 C).

Additionally we would like to see children of any age with a fever over 104 F (40 C).  Fever with a new rash, fever lasting more than 7 days and fever in children with other chronic medical problems are all reasons for us to evaluate a child in person.

Are there medications for fever?
Acetaminophen (Tylenol) and Ibuprofen (Motrin, Advil) can lower fever by 2-3 degrees. If children appear well and are behaving normally it is not always necessary to treat their fever. When infants and children have a fever they do often appear ill and fussy and treating their fever can relieve pain, achiness and malaise and sometimes improve feeding behavior.

How much medication should I give?
Dosing is based on weight, but manufacturers are reluctant to provide dosing for infants.  We have provided the age and weight based dosing below for the use of our established patients as a reference for use in consultation with us. Please remember we want to see any infant younger than 3 months with a fever, and any infant or child who is so ill their parents are worried in person at our office.

Mistakes in dosing can occur when the concentration and measurement of medication is not properly confirmed. Mistakes in the timing between doses can lead to overdose as well. Acetaminophen and Ibuprofen can be administered together or alternated on an every 3 to 4 hour schedule.  Alternating doses is very effective but  increases the risk of accidentally overdosing by giving the same medication twice in a row.

For Acetaminophen (Tylenol) labeled 160 mg/5 ml and Ibuprofen (Motrin/Advil) labeled 100 mg/5 ml

5-11 pounds……….. 0-3 months………… 1.25 ml (1/4 tsp) every 6 hours

12-17 pounds……… 4-11 months……….. 2.5 ml (1/2 tsp) every 6 hours

18-23 pounds……… 12-23 months……… 3.75 ml (3/4 tsp) every 6 hours

24-35 pounds……… 24-36 months…….. 5 ml (1 tsp) every 6 hours


There is an older version of Acetaminophen with a concentration of 80 mg/0.8 ml.    This is over 3 x as concentrated, so the dose volumes are much lower. This is the one marketed as infant drops, and is no longer being produced.

5-11 pounds……….. 0-3 months………… 0.4 ml every 6 hours

12-17 pounds……… 4-11 months………. 0.8 ml every 6 hours

18-23 pounds…….. 12-23 months……… 1.2 ml every 6 hours

24-35 pounds……… 24-36 months…….. 1.6 ml every 6 hours


Taking care of an ill infant or toddler is a difficult responsibility and we are always here to help!