Guide
Fever in babies: when to call the doctor
Call your pediatrician right away if a baby under 3 months (12 weeks) has a temperature of 100.4°F (38.0°C) or higher. For older babies and children, the AAP advises calling if a fever lasts more than 24 hours under age 2, more than 3 days from age 2, rises above 104°F (40°C) repeatedly, or comes with symptoms like a stiff neck, trouble breathing, an unexplained rash or repeated vomiting.
Source: American Academy of Pediatrics
When to call, by age
| Age | Call the pediatrician if |
|---|---|
| Under 3 months | Any temperature of 100.4°F (38.0°C) or higher. Call right away, before giving any medicine. |
| 3 months to 2 years | Fever lasts more than 24 hours, rises above 104°F (40°C) repeatedly, or comes with any warning sign below. |
| 2 years and older | Fever lasts more than 3 days (72 hours), rises above 104°F (40°C) repeatedly, or comes with any warning sign below. |
Warning signs at any age
- Stiff neck, severe headache, severe sore throat or severe ear pain.
- Trouble breathing, an unexplained rash, or repeated vomiting or diarrhea.
- Your child is very hard to wake, won’t drink, or seems very sick to you.
Call 911 for a child who is struggling to breathe, can’t be woken, or has a seizure that doesn’t stop.
Why young babies are different
In the first months of life, a fever can be the only sign of a serious infection. The AAP has a dedicated clinical guideline for well-appearing babies 8 to 60 days old with a fever of 38.0°C or higher, which is why doctors want to see young babies with a fever promptly, even when they seem well.
Taking a temperature
A rectal temperature is the most reliable in babies. Ear, forehead and armpit readings are useful for screening but are less accurate. Normal rectal temperature runs 36.6 to 38.0°C (97.9 to 100.4°F).
What fever medicine is for
Fever itself is the body’s response to infection. The AAP’s clinical report on fever says the point of fever medicine is to make your child more comfortable. The thermometer doesn’t have to read normal. If your child is comfortable, drinking and sleeping, a fever doesn’t need to be treated.
For babies 3 months and older, use the Tylenol chart. From 6 months, Motrin is an option too.
Common questions
What temperature is a fever in a baby?
A rectal temperature of 100.4°F (38.0°C) or higher. In a baby under 3 months (12 weeks), that is a reason to call the doctor right away.
Should I give Tylenol before calling the doctor?
Not for a baby under 12 weeks. Call first: medicine can hide a fever the doctor needs to know about. For older children, fever medicine is for comfort, and you can use the Tylenol or Motrin chart.
How long can a fever last in a toddler?
The AAP advises calling the pediatrician if a fever lasts more than 24 hours in a child under 2, or more than 3 days (72 hours) in a child 2 or older.
Sources
- When to Call the Pediatrician: Fever. American Academy of Pediatrics, HealthyChildren.org (updated 2 Dec 2022). Checked 2026-09-25.
- Evaluation and Management of Well-Appearing Febrile Infants 8 to 60 Days Old (Pantell et al.). American Academy of Pediatrics, Pediatrics 2021;148(2):e2021052228. Checked 2026-09-25.
- Fever and Antipyretic Use in Children (Sullivan, Farrar). American Academy of Pediatrics clinical report, Pediatrics 2011;127(3):580-587. Checked 2026-09-18.
- Pediatric Vital Signs Reference Chart (Novak, Gill; edited 2020), citing PALS Guidelines 2015 and CPS 2015. PedsCases. Checked 2026-09-25.