Is an axillary temperature of 98.5 degrees Fahrenheit considered elevated?

Is an Axillary Temperature of 98.5°F Considered Elevated?

An axillary temperature of 98.5°F (36.9°C) is not considered elevated or febrile and falls within the normal range for axillary temperature measurements.

Understanding Normal Temperature Ranges by Measurement Site

Temperature readings vary significantly based on the measurement site. According to clinical guidelines, normal temperature ranges differ by location:

• Axillary (armpit): 35.01-36.93°F (normal range) 1
• Oral: 35.73-37.41°F 1
• Rectal: 36.32-37.76°F 1

Axillary temperatures are typically lower than oral or rectal temperatures, with axillary readings averaging about 0.85°F lower than oral temperatures 2.

Why 98.5°F Axillary Is Not Considered Fever

Several factors support that 98.5°F axillary is within normal limits:

1. Clinical Guidelines Definition: According to the Infectious Diseases Society of America guidelines, fever in adults is defined as:

   • A single oral temperature >100°F (37.8°C) 3
   • An axillary temperature >99.5°F (37.5°C) 3
   • An increase in temperature of ≥2°F (≥1.1°C) over baseline 3

2. Normal Variation: There is considerable individual variation in normal body temperature. Research shows mean temperatures across individuals range from 95.4°F to 99.3°F 4, with 77% of people having mean temperatures at least 1°F lower than the traditional 98.6°F 4.

3. Measurement Site Considerations: Axillary temperatures can be up to 2.6°F lower than oral temperatures 2, making 98.5°F axillary equivalent to a normal oral temperature.

Factors That Influence Normal Body Temperature

Several factors can affect what's considered "normal" for an individual:

• Gender: Women tend to have slightly higher normal temperatures than men (mean 98.5°F vs. 98.3°F) 2, 5
• Age: Older adults (≥60 years) have lower temperatures than younger adults by 0.23°C on average 1
• Time of day: Temperature varies diurnally, with early morning nadir and late afternoon peak 5
• Individual baseline: Each person has their own normal temperature range that remains relatively stable 4

Clinical Implications

When evaluating whether a temperature is elevated:

• Consider the individual's baseline temperature when available
• Factor in the measurement method (axillary vs. oral vs. rectal)
• Remember that axillary temperatures are typically lower than core temperatures
• Consider other clinical signs of infection or inflammation

Common Pitfalls to Avoid

• Assuming 98.6°F is "normal" for everyone: Research shows this historical standard is too high for many people 5
• Failing to account for measurement site: Axillary temperatures are consistently lower than oral or rectal temperatures 2, 1
• Ignoring individual variation: There is significant person-to-person variability in normal temperature 4
• Not considering time of day: Normal temperature fluctuates throughout the day 5

For accurate temperature assessment, healthcare providers should ideally use core temperature monitoring methods when available, as these provide the most reliable measurements 3. When these are not available, oral or rectal measurements are preferred over axillary measurements, which are less reliable 3.