Key Takeaways
- Any fever (100.4°F/38°C+) in a baby under 3 months needs immediate medical attention
- Rectal temperature is the most accurate method for babies under 1 year
- How your baby acts matters more than the number on the thermometer
- Never give aspirin to babies or children
Your baby feels warm. Your heart starts racing. Before you panic, here's exactly what you need to know about baby fevers — when to worry, when to wait, and what to do.
Normal Baby Temperature Ranges
| Method | Normal Range | Fever |
|---|---|---|
| Rectal (most accurate) | 97.9–100.3°F (36.6–37.9°C) | 100.4°F (38°C)+ |
| Oral | 97.6–99.6°F (36.4–37.6°C) | 100°F (37.8°C)+ |
| Armpit (axillary) | 96.6–98°F (35.9–36.7°C) | 99°F (37.2°C)+ |
| Ear (tympanic) | 97.5–100.4°F (36.4–38°C) | 100.4°F (38°C)+ |
| Forehead (temporal) | 97.3–100.1°F (36.3–37.8°C) | 100.4°F (38°C)+ |
Rectal is the gold standard
For babies under 1 year, the AAP recommends rectal temperature as the most reliable method. Forehead and ear thermometers are convenient but less accurate in infants.
See also: Baby Sweating While Sleeping: Causes & When to Worry and Baby Hair Pulling & Head Banging: Why They Do It & When to Worry.
Fever Thresholds by Age
| Age | Temperature | Action |
|---|---|---|
| Under 3 months | 100.4°F (38°C)+ | 🚨 Call doctor or go to ER immediately |
| 3–6 months | 100.4°F (38°C)+ | Call your pediatrician |
| 3–6 months | 102°F (38.9°C)+ | Call doctor promptly |
| 6–24 months | 102°F (38.9°C)+ | Call if lasts more than 1 day |
| Any age | 104°F (40°C)+ | 🚨 Seek immediate medical care |
Under 3 months = always call
A fever in a baby under 3 months old is always an emergency. Their immune system is still developing and infections can progress quickly. Don't wait — call your pediatrician or go to the ER.
How to Take Your Baby's Temperature
Rectal (recommended for babies)
- Apply petroleum jelly to the thermometer tip
- Lay baby face-down on your lap or face-up with legs held up
- Insert gently, about 0.5–1 inch (1–2.5cm)
- Hold in place until the thermometer beeps
Forehead (quick screening)
- Swipe across the forehead per manufacturer instructions
- Good for quick checks, but confirm with rectal if reading seems high
When to Call the Doctor vs ER
Go to the ER
- Any fever in a baby under 3 months
- Temperature over 104°F (40°C) at any age
- Baby is limp, unresponsive, or difficult to wake
- Difficulty breathing
- Seizure
- Purple spots on the skin
Call your pediatrician
- Fever lasting more than 24 hours (6–24 months) or 3 days (over 24 months)
- Baby is unusually irritable or lethargic
- Not drinking fluids or fewer than 4 wet diapers in 24 hours
- Fever keeps coming back
- You're worried — trust your instincts
Safe Fever Treatment for Babies
| Medication | Age | Notes |
|---|---|---|
| Acetaminophen (Tylenol) | 2+ months | Dose by weight, not age. Ask your pediatrician |
| Ibuprofen (Advil/Motrin) | 6+ months | Dose by weight. Can alternate with acetaminophen |
| Aspirin | ❌ Never | Risk of Reye's syndrome in children |
Always dose by weight
Ask your pediatrician for the correct dose based on your baby's current weight. Over-the-counter dosing charts can be inaccurate for small babies.
Home Comfort Measures
- Light clothing — don't bundle up a feverish baby
- Fluids — offer breast milk, formula, or water (6+ months) frequently
- Lukewarm bath — can help bring temperature down. Never use cold water or alcohol
- Rest — let baby sleep as much as they want
- Monitor — check temperature every 4 hours and watch for warning signs
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.
