What is the normal body temperature range for children?

Normal Body Temperature Range for Children

The normal body temperature range for children varies by age and measurement site, with rectal temperature of 36.5-37.5°C (97.7-99.5°F) representing the target range for maintaining optimal physiologic function, though healthy children may have temperatures up to 38.0°C (100.4°F) without clinical significance. 1, 2

Age-Specific Normal Temperature Ranges

Infants Under 3 Months

• Rectal temperature (gold standard): 36.7-37.9°C (98.1-100.2°F) represents the normal range in healthy infants 3
• Mean rectal temperature is 37.5°C ± 0.3°C 2
• The 95th percentile is 38.0°C, meaning 6.5% of healthy infants may have temperatures at or above this level 2
• Temperature increases slightly with age even in this young group:
  • Birth to 30 days: upper limit 38.0°C 2
  • 31-60 days: upper limit 38.1°C 2
  • 61-91 days: upper limit 38.2°C 2

Term Newborns (First 24 Hours)

• Median rectal temperature: 36.9-37.1°C (98.4-98.8°F) during the first day of life 4
• Normal range (2.5-97.5 percentile): 35.7-37.9°C at 2 hours, stabilizing to 36.5-37.7°C by 24 hours 4
• Critical threshold: Temperatures below 36.5°C represent hypothermia/cold stress requiring intervention 1, 4

Older Children

• Oral temperature: ≥37.6°C warrants concern and may require rectal confirmation 5
• Normal oral temperature: approximately 37.5°C 6

Measurement Site Differences

Rectal (Most Accurate for Core Temperature)

• Recommended as gold standard for infants and young children under 3 years 7, 5, 1
• Rectal temperature is 0.7°C (range 0-3°C) higher than axillary on average 3
• Safer than historically believed, with perforation occurring in less than 1 in 2 million measurements 3

Axillary (Least Reliable)

• Normal range: 35.6-37.2°C in infants under 6 months 3
• Not recommended for accurate core temperature assessment, as it has only 73% sensitivity for detecting fever compared to rectal measurement 3
• May underestimate core temperature and should be confirmed rectally when concerning 1

Tympanic

• Fever threshold: ≥38.0°C 6
• Preferred site in some settings as it reflects hypothalamic temperature 8

Clinical Context and Physiologic Factors

Environmental and Seasonal Variations

• Temperature varies significantly by season, being higher in summer (upper limit 38.3°C) than winter (upper limit 38.0°C) 2
• Room temperature of 23-25°C (73-77°F) should be maintained for infants 1

Risk Factors for Temperature Deviations

Hypothermia risk factors (<36.5°C): 4

• Low birth weight (OR 3.1 per kg)
• Male sex
• Being born at night
• Nursed in cot versus skin-to-skin

Hyperthermia risk factors (>37.5°C): 4

• High birth weight (OR 2.2 per kg)
• Being awake
• Skin-to-skin care (after 8 hours of life)

Critical Clinical Thresholds

Fever Definition

• Under 3 years: Rectal temperature ≥38.0°C (100.4°F) 7, 5
• Older children: Oral temperature ≥37.6°C 5

Hypothermia Definition

• Core temperature <36.5°C (97.7°F) represents cold stress requiring immediate intervention 1
• Temperature <35°C (95°F) indicates progression to true hypothermia requiring urgent medical evaluation 1

Hyperthermia in Neonatal Resuscitation

• Target range: 36.5-37.5°C for preterm infants 7
• Avoid hyperthermia >38.0°C due to associated risks 7

Important Clinical Pitfalls

• Do not dismiss mild temperature abnormalities in infants, as even modest hypothermia increases mortality risk by 28% for each 1°C below 36.5°C 1
• Clinical appearance matters more than precise temperature in determining illness severity 5, 9
• Response to antipyretics does not correlate with likelihood of serious bacterial infection and should not provide false reassurance 9
• Hypothermia in critically ill children requires core temperature ≥35°C (95°F) before brain death evaluation 7