Baby Fever Guide

Fever is the body's natural response to infection. Here's what you need to know about managing your baby's fever safely.

1. What is a Fever?

A fever is defined as a rectal temperature of 100.4°F (38°C) or higher. Fever itself is not an illness—it's a sign that the body is fighting an infection.

Normal body temperature ranges:

• Rectal: 97.9°F - 100.4°F (36.6°C - 38°C)
• Oral: 95.9°F - 99.5°F (35.5°C - 37.5°C)
• Armpit: 94.5°F - 99.1°F (34.7°C - 37.3°C)
• Ear: 96.4°F - 100.4°F (35.8°C - 38°C)

2. How to Take Baby's Temperature

For the most accurate reading in babies, rectal temperature is the gold standard.

Rectal Temperature (Most Accurate for Babies)

1. Use a digital thermometer with a flexible tip
2. Apply petroleum jelly to the tip
3. Lay baby face-down across your lap or on their back with legs up
4. Insert thermometer 1/2 to 1 inch into rectum
5. Hold in place until thermometer beeps (about 1 minute)

Armpit Temperature (Alternative)

Place thermometer in dry armpit, hold arm against body for 4-5 minutes. Add 1°F (0.5°C) to the reading for approximate rectal equivalent.

3. When to Call the Doctor

Call immediately if:

• Baby is under 3 months with any fever (100.4°F/38°C+)
• Baby is 3-6 months with fever of 102°F (38.9°C) or higher
• Fever reaches 104°F (40°C) or higher at any age
• Fever lasts more than 3 days
• Baby is unusually irritable, lethargic, or difficult to wake
• Baby refuses to drink fluids
• Baby has a rash, stiff neck, or difficulty breathing
• Baby has had a febrile seizure

4. Treating Fever at Home

Fever doesn't always need to be treated—focus on keeping baby comfortable.

Comfort Measures

• Keep hydrated: Offer breast milk, formula, or Pedialyte frequently
• Dress lightly: One layer of clothing; avoid bundling
• Cool environment: Keep room comfortable, not too hot
• Lukewarm bath: Can help but avoid cold water (causes shivering)
• Rest: Let baby sleep as needed

Fever-Reducing Medications

Acetaminophen (Tylenol) — For babies 2 months and older:

• Dose based on baby's weight, not age
• Can give every 4-6 hours as needed
• Maximum 5 doses in 24 hours

Ibuprofen (Advil, Motrin) — For babies 6 months and older:

• Dose based on baby's weight
• Can give every 6-8 hours as needed
• Give with food to avoid stomach upset

5. Fever After Vaccinations

Low-grade fever (under 102°F/38.9°C) is common and normal after vaccinations. It usually appears within 24 hours and resolves within 1-2 days.

• Acetaminophen can be given for discomfort
• Some pediatricians recommend preventive dosing
• Call doctor if fever is high or lasts more than 3 days

6. Febrile Seizures

Febrile seizures affect 2-5% of children and are caused by rapid temperature changes. They look frightening but rarely cause lasting harm.

If a seizure occurs:

• Place baby on their side on a safe surface
• Do NOT put anything in baby's mouth
• Time the seizure
• Call 911 if seizure lasts more than 5 minutes
• Always call your doctor after a febrile seizure