What is Normal Body Temperature and How to Accurately Measure It
Introduction
Body temperature is an important health indicator, and its accurate measurement sometimes plays a key role in diagnosis and treatment. Understanding the range of normal body temperature and the methods for measuring it can help in the timely detection of illnesses and in making informed health-related decisions.
Normal Body Temperature
Body temperature varies slightly from person to person, and there is no single level that is considered normal for everyone. Typically, a normal body temperature is between 35.5 and 37.5°C (95.9–99.5°F), although older adults often have slightly lower temperatures.
It is generally accepted that normal body temperature is around 36.6°C (97.9°F), but studies show that this value can vary depending on the method of measurement:
- Tympanic (in the ear): 35.7–37.5°C (96.3–99.5°F)
- Oral: 35.7–37.4°C (96.3–99.3°F)
- Axillary (under the arm): 35.0–36.9°C (95.0–98.4°F)
- Rectal: 36.3–37.7°C (97.3–99.9°F)
It's important to note that body temperature can fluctuate throughout the day and is affected by several factors, including physical activity, time of day, and even emotional state. For example, body temperature tends to be lower in the morning and higher in the late afternoon or evening. Hormonal changes, such as during the menstrual cycle or pregnancy, can also affect body temperature. In addition, environmental conditions such as exposure to cold or heat can cause temporary changes in temperature, so it's important to measure under consistent conditions for accurate results.
How to Accurately Measure Temperature
There are several methods for measuring body temperature, but their accuracy can vary significantly.
Tympanic thermometers (ear thermometers)
These thermometers measure temperature in the ear canal and are considered among the most accurate. They show good agreement with medical-grade reference devices, making them a reliable choice for regular temperature measurement.
Peripheral thermometers (oral and axillary)
It is worth noting that peripheral thermometers may not provide the most accurate readings, with the potential for underestimating actual body temperature. Compared to central thermometers, such as rectal thermometers, they may offer less precision.
Non-contact infrared thermometers (NCITs)
These thermometers are convenient because they do not require skin contact, but their accuracy can vary. To obtain reliable data, it is important that the device is properly calibrated and used under appropriate conditions.
Central thermometers
Rectal and intravascular thermometers are widely regarded as the most accurate methods for measuring core body temperature. However, due to their invasive nature and potential discomfort, these methods are not commonly used in everyday situations. They are typically reserved for medical facilities and specialized cases.
Conclusion
Accurately measuring body temperature is crucial for monitoring health and detecting potential illnesses. While the normal range of body temperature can vary depending on the person and method of measurement, understanding these variations and using the most suitable thermometer for the situation can help ensure precise readings. Tympanic and central thermometers offer higher accuracy, while peripheral and non-contact infrared thermometers provide convenience, though with potentially lower precision. By knowing when and how to measure body temperature effectively, individuals can make more informed health decisions and catch signs of illness early.
Recourses
Geneva, I., Cuzzo, B., Fazili, T., & Javaid, W. (2019). Normal Body Temperature: A Systematic Review. _Open Forum Infectious Diseases_, 6. [https://doi.org/10.1093/ofid/ofz032](https://doi.org/10.1093/ofid/ofz032).
Lu, S., Leasure, A., & Dai, Y. (2010). A systematic review of body temperature variations in older people.. _Journal of clinical nursing_, 19 1-2, 4-16 . https://doi.org/10.1111/j.1365-2702.2009.02945.x.
Lenhardt, R., & Sessler, D. (2006). Estimation of Mean Body Temperature from Mean Skin and Core Temperature. _Anesthesiology_, 105, 1117-1121. [https://doi.org/10.1097/00000542-200612000-00011](https://doi.org/10.1097/00000542-200612000-00011).
Niven, D., Gaudet, J., Laupland, K., Mrklas, K., Roberts, D., & Stelfox, H. (2015). Accuracy of Peripheral Thermometers for Estimating Temperature. _Annals of Internal Medicine_, 163, 768-777. https://doi.org/10.7326/M15-1150.
