What is the normal range for body temperature?

Normal Range for Body Temperature

The normal range for body temperature in humans is 36.0°C to 37.5°C (96.8°F to 99.5°F), with 37°C (98.6°F) considered the traditional average normal body temperature. However, this range varies based on measurement site, individual factors, and time of day.

Measurement Site Variations

Different body sites yield different temperature readings:

• Rectal: 36.32°C to 37.76°C (most accurate reflection of core temperature) 1
• Oral: 35.73°C to 37.41°C 1
• Tympanic: 35.76°C to 37.52°C 1
• Axillary: 35.01°C to 36.93°C (least accurate) 1
• Urine: 35.61°C to 37.61°C 1

Normothermic Range by Age and Situation

• Adults: 35.73°C to 37.41°C (oral measurement) 1
• Older adults (≥60 years): Average 0.23°C lower than younger adults 1
• Normothermic range for clinical purposes: 35°C to 38°C (95°F to 100.4°F) 2
• Fever threshold: ≥38°C (100.4°F) or an increase of at least 1.1°C (2°F) above baseline 2

Factors Affecting Body Temperature

1. Age: Older adults typically have lower baseline temperatures 1
2. Time of day: Temperature is typically lowest in early morning and highest in late afternoon/evening 3
3. Sex: Women tend to have slightly higher temperatures than men 4
4. Individual variation: Mean temperatures can range from 35.2°C to 37.4°C across individuals 4
5. Measurement method: Different techniques yield different readings 5

Important Clinical Considerations

• Recent research shows the traditional 37°C (98.6°F) may be too high for many individuals, with a study finding a mean temperature of 36.1°C (97.0°F) across participants 4
• 77% of individuals in one study had mean temperatures at least 0.55°C (1°F) lower than the traditional 37°C 4
• Individual temperature remains relatively stable within a person over time 4

Pitfalls in Temperature Assessment

• Using a single "normal" temperature standard for all patients can lead to missed fevers in those with naturally lower baseline temperatures 4
• Peripheral sites (axillary, forehead) are not recommended for core temperature assessment in adults 6
• Frail elderly individuals often have lower normal temperatures and may be incorrectly assessed as non-febrile despite significant relative temperature elevations 6

Best Practices for Temperature Measurement

• Use the same measurement site consistently for an individual patient 3
• Consider the patient's baseline temperature when possible 4
• For critical assessment, central methods (pulmonary artery catheter, urinary catheter, esophageal) provide the most accurate readings 2
• For routine assessment, oral or rectal measurements are preferred over axillary or tympanic 2

Temperature assessment should be interpreted in the context of the individual's baseline, age, measurement site, and clinical presentation rather than relying solely on standard cutoffs.