Key Takeaways
- Any fever in a baby under 3 months (38°C / 100.4°F or higher) is an emergency — call immediately
- Difficulty breathing, blue lips, or grunting sounds need urgent care
- Fewer than 6 wet diapers in 24 hours, sunken fontanelle, or no tears when crying suggest dehydration
- When in doubt, call — pediatricians expect calls from new parents and would rather hear from you early
One of the hardest parts of being a new parent is knowing when something is "normal baby stuff" and when it's time to call the doctor. This guide covers the specific signs and thresholds that pediatricians say warrant a call.
Fever: When Is It Serious?
Fever is the number one reason parents call the pediatrician — and the rules change dramatically based on your baby's age.
See also: Preeclampsia: Warning Signs, Risk Factors & When to Call Your Doctor and Preparing Your Toddler for a New Sibling: A Complete Guide.
| Baby's Age | Temperature | Action |
|---|---|---|
| Under 3 months | 38°C (100.4°F) or higher | Call immediately or go to ER |
| 3–6 months | 38.3°C (101°F) or higher | Call your pediatrician |
| 6–24 months | 39°C (102.2°F) or higher | Call if it lasts more than 1 day |
| Any age | 40°C (104°F) or higher | Call immediately |
How to take temperature accurately
For babies under 3 months, the AAP recommends a rectal thermometer for the most accurate reading. For older babies, an ear or forehead thermometer is acceptable.
Also call regardless of temperature if your baby has a fever AND:
- Is unusually lethargic or difficult to wake
- Has a rash that doesn't fade when pressed
- Has had a febrile seizure
- Has been feverish for more than 3 days
- Has a weakened immune system or chronic condition
Breathing Problems
- Rapid breathing — more than 60 breaths per minute in a newborn
- Retractions — skin pulling in between the ribs with each breath
- Nasal flaring — nostrils widening with each breath
- Grunting — a sound at the end of each breath
- Blue or gray color — around the lips, tongue, or fingernails
- Pauses in breathing — lasting more than 10 seconds
Blue lips = emergency
If your baby's lips, tongue, or face turn blue or gray, call emergency services immediately.
Dehydration Warning Signs
- Fewer than 6 wet diapers in 24 hours
- Dark yellow urine
- Dry mouth and lips
- No tears when crying
- Sunken fontanelle
- Sunken eyes
- Unusual sleepiness
Vomiting and Diarrhea
Vomiting — call if:
- Vomit is green (bile-stained)
- Vomit contains blood
- Projectile vomiting in a baby under 4 months
- Vomiting after a head injury
- Can't keep fluids down for 8+ hours
- Vomiting with fever and lethargy
Diarrhea — call if:
- More than 8 watery stools in 8 hours
- Blood or mucus in the stool
- Diarrhea with fever above 38.3°C
- Signs of dehydration
- Diarrhea lasting more than 2 days
Rashes That Need Attention
- Petechiae — tiny dots that don't fade when pressed. Can indicate serious infection
- Widespread rash with fever
- Hives with swelling — especially around face or throat
- Blisters or pus-filled bumps
- Rash that spreads rapidly
The glass test
Press a clear glass against a rash. If the spots don't fade under pressure, call your doctor immediately.
Behavior Changes to Watch For
- Inconsolable crying — lasting more than 3 hours, or a different-sounding cry
- Unusual lethargy — difficult to wake, floppy, unresponsive
- Refusing to eat — missing 2+ feedings in a row
- Stiff neck or body
- Bulging fontanelle
Always Call For These
- Under 3 months with any fever (38°C+)
- Blue or gray skin, lips, or tongue
- Difficulty breathing or pauses in breathing
- A seizure
- Unresponsive or extremely difficult to wake
- Bulging fontanelle
- Green (bile) vomit
- Blood in stool or vomit
- Exposure to a toxic substance
Trust Your Instincts
Pediatricians consistently say: if something feels wrong, call. You don't need a specific symptom from a checklist. Parents who say "something just isn't right" are often correct.
Your pediatrician's office has a nurse line for after-hours calls. Use it.
AI-Powered Health Tracking for Peace of Mind
Log symptoms, medications, and temperatures. ParAI's AI helps you spot patterns and know when to call the pediatrician — based on AAP guidelines.
Disclaimer: This article is for informational purposes only and does not replace professional medical advice. Always consult your pediatrician for concerns about your baby's health or development.
