Baby Fever: When to Worry, What to Do, and When to Go to the ER

Fever is a symptom, not a diagnosis. Your job is to measure correctly, check age-based risk, and watch for red flags. This guide gives you a clear plan.

Step 1 — Measure temperature the right way

• 0–3 months: use a rectal thermometer for the most accurate reading
• 3+ months: rectal is still most accurate; other methods can be used if done correctly
• Avoid guessing based on “warm forehead”

Step 2 — Know what counts as fever

• Fever generally means 38.0°C (100.4°F) or higher (measured accurately)

Step 3 — Act by age (this is the part parents miss)

0–28 days

• Any fever (≥38.0°C / 100.4°F) needs urgent medical evaluation

29–90 days

• Fever needs same-day medical guidance, even if your baby looks “fine”
• Risk is lower than newborns, but still significant

3 months and older

• Look at hydration, breathing, energy level, and red flags
• Fever alone is less important than how your child looks and behaves

Step 4 — Red flags that should push you to urgent care

Step 5 — Safe home care (when your child is stable)

• Offer fluids often (breastmilk/formula for infants; water/oral fluids for older children)
• Dress lightly; avoid over-bundling
• Focus on comfort, not “chasing the number”
• Use fever medicine only when appropriate for age and weight
• Avoid cold baths or rubbing alcohol

Common mistakes that delay care

• Waiting too long in young babies because they still feed
• Using unreliable temperature methods and assuming it’s “not real” fever
• Ignoring hydration changes and breathing changes