Normal Body Temperature Ranges in Pediatric Patients by Age
The normal body temperature in children varies by age and measurement route, with rectal temperatures ranging from 36.7-37.9°C (98.1-100.2°F) being considered normal, and fever defined as ≥38.0°C (100.4°F) in most pediatric age groups, though age-specific thresholds should be applied for optimal accuracy. 1, 2
Age-Specific Normal Temperature Ranges
Infants 0-3 Months (Rectal Measurement)
- Normal range: 36.7-37.9°C (98.1-100.2°F) 1
- Mean temperature: 37.5°C ± 0.3°C 3
- Fever threshold varies by specific age within this group: 3
- Birth to 30 days: ≥38.0°C (100.4°F)
- 31-60 days: ≥38.1°C (100.6°F)
- 61-91 days: ≥38.2°C (100.8°F)
- The 95th percentile is 38.0°C, meaning temperatures ≥38.1°C fall above the 95th percentile 3
- Critical clinical point: Infants <3 months with temperatures ≥38.0°C are at higher risk for serious bacterial infections and require urgent evaluation 2, 4
Infants 0-2 Months (Special Considerations)
- This age group demonstrates statistically higher temperatures compared to older children 5
- 99th percentile values: 5
- Axillary: 37.5°C (99.5°F)
- Tympanic: 37.85°C (100.1°F)
Children 1-18 Years
Axillary (armpit) measurements: 6, 5
- Median: 36.7°C (98.1°F) 6
- Mean: 36.04°C (range 35.0-37.6°C) 5
- 95th percentile: 36.8°C 5
- 99th percentile: 37.0°C 5
- 99.9th percentile: 38.5°C 6
Tympanic (ear) measurements: 5
- Mean: 36.91°C (range 35.15-37.9°C)
- 95th percentile: 37.6°C
- 99th percentile: 37.8°C
Rectal measurements (when used): 6
- Median for infants ≤12 months: 37.2°C (99.0°F)
- 99th percentile for infants: 37.8°C (100.0°F)
Measurement Route Considerations
Route-Specific Temperature Differences
- Rectal temperatures run approximately 0.4°C higher than axillary temperatures in infants 6
- Axillary temperatures are approximately 0.1°C lower than other routes in children 1-18 years 6
- Current ear thermometers are equivalent to rectal thermometers in infants <6 months 7
Age-Appropriate Measurement Methods
- Rectal measurement is the gold standard for children <4 years, providing the closest approximation to core body temperature 1
- At age 4 years, oral temperature measurement becomes acceptable and preferred if the child can cooperate (hold thermometer under tongue with mouth closed) 1
- Axillary and tympanic measurements are acceptable alternatives but require route-specific fever thresholds 5, 7
Clinical Application: Fever Thresholds by Route
Rectal (preferred for accuracy in young children): 1, 2
- Fever: ≥38.0°C (100.4°F) for most ages
- Age-adjusted thresholds provide better sensitivity 3
Axillary: 5
- Fever: >37.0°C (98.6°F) for children >2 months
- Fever: >37.5°C (99.5°F) for infants 0-2 months
Tympanic: 5
- Fever: >37.8°C (100.0°F) for children >2 months
- Fever: >37.85°C (100.1°F) for infants 0-2 months
Important Clinical Caveats
Factors That Do NOT Significantly Affect Temperature
- Sex, time of day, and specific age within broader age groups show no clinically significant temperature variation in adjusted analyses 6
- Height and duration of fever are not predictive parameters for major illness 4
Factors That DO Affect Temperature
- Season: Temperatures are higher in summer (2 SD above mean = 38.3°C) than winter (2 SD above mean = 38.0°C) 3
- Recent antipyretic use may mask true fever, making accurate assessment critical 2
Common Pitfalls to Avoid
- Do not use a fixed 38.0°C threshold across all ages and routes - age-based and route-specific thresholds improve diagnostic accuracy 7
- Any temperature suggesting fever by alternative methods should be confirmed with rectal or oral measurement before making critical clinical decisions 1
- Do not delay evaluation in high-risk groups (infants <3 months with fever ≥38.0°C) even if temperature seems marginally elevated 2, 4