Fever rules by age

Under 3 months: any rectal temperature of 100.4°F (38°C) or higher is a same-day pediatric visit or ER trip. Newborn immune systems can't yet fight infections effectively, and fever at this age can signal something serious. Between 3 and 6 months: call for fever over 101°F (38.3°C) or any fever lasting more than 24 hours. Between 6 and 24 months: call for fever over 102°F (38.9°C), or any fever paired with poor feeding, unusual sleepiness, rash, or trouble breathing. Overall, look at the child, not the number. A child with 103°F who is playful and drinking is usually less concerning than one with 100.5°F who is lethargic and refusing fluids. Trust your instincts — call when something feels off.