What Are Temperature Checks? A Guide to Their Role in General Health

September 30, 2025 •

4 min read

While the widely cited 'normal' body temperature of 98.6°F (37°C) has been updated by recent research to a slightly lower average, understanding your personal baseline is key to effective health monitoring. Knowing what are temperature checks involves understanding various methods for measuring body heat, which can serve as a vital indicator of your overall health.

Quick Summary

A temperature check is the process of measuring a person's body heat to screen for fever, a common sign of illness. It can be performed using various devices, including digital, infrared, or temporal artery thermometers. The method and accuracy vary depending on the device and site of measurement.

Key Points

Normal temperature varies: The long-held standard of 98.6°F is no longer considered universal; normal temperature can range between 97°F and 99°F for adults and fluctuates based on age, activity, and time of day.
Multiple thermometer types exist: Digital, infrared (temporal and tympanic), and wearable thermometers offer varying levels of accuracy, speed, and invasiveness for different situations.
Accuracy depends on the site: Rectal temperature is generally the most accurate measurement of core body temperature, especially for infants. Underarm and forehead readings are less precise and better for screening purposes.
Screening has limitations: Temperature checks alone are ineffective for detecting all illnesses, as many sick individuals—including asymptomatic carriers—may not have a fever. They should not be used as a replacement for comprehensive screening.
Fever is a symptom, not a diagnosis: An elevated temperature (typically above 100.4°F for adults) indicates that the immune system is fighting an infection or illness, but it doesn't specify the cause.
Proper technique is essential: Achieving an accurate reading requires following device instructions carefully, such as waiting to take an oral temperature after eating or drinking, or ensuring proper distance for a non-contact thermometer.

The Role of Temperature in Health and Wellness

Body temperature is one of the body's seven universally accepted vital signs, providing a basic but important window into your health. The body's complex thermoregulation system works to maintain a stable internal temperature, which is crucial for all bodily functions. A significant deviation from this norm can signal a problem, such as an infection, inflammation, or other physiological changes. Regular temperature checks, therefore, serve as a foundational tool for monitoring one's health.

Historically, the oral temperature of 98.6°F (37°C) was considered the gold standard for 'normal,' but recent studies indicate a slight decrease in average human body temperature over time. Furthermore, a person's temperature naturally fluctuates throughout the day due to factors like physical activity, time of day, and age. Establishing a personal baseline is more effective for detecting abnormalities than relying on a single, universal number.

Types of Thermometers and Measurement Sites

Technology has evolved from simple mercury-in-glass devices to a variety of modern, safer, and more convenient thermometers. The method and location for taking a temperature can affect the reading's accuracy, with some sites providing a better reflection of core body temperature than others.

Digital Thermometers

These electronic devices are a staple in modern households and medical settings. They use a heat-sensitive electronic sensor to record body temperature and display the reading on a digital screen. They can be used for several measurement sites:

Oral: Placed under the tongue, this is a common method for older children and adults. For an accurate reading, avoid eating or drinking hot or cold fluids for at least 15 minutes prior.
Rectal: Considered the most accurate method, especially for infants and young children, as it reflects core body temperature more closely. The thermometer is gently inserted into the rectum.
Axillary (Underarm): A less accurate but non-invasive option, often used for screening. Readings here are typically lower than oral or rectal measurements.

Infrared Thermometers

Infrared (IR) thermometers measure the thermal radiation emitted by a person's body, inferring temperature without any physical contact. This non-invasive feature gained significant popularity during the COVID-19 pandemic for screening purposes. There are two main types:

Temporal Artery (Forehead): The device is swept across the forehead, measuring the heat from the temporal artery. Factors like sweating or direct sunlight can affect accuracy.
Tympanic (Ear): Placed inside the ear canal to measure the infrared heat radiating from the eardrum. It is a quick method, but earwax or improper technique can interfere with results.

Wearable Thermometers

These devices, often worn as patches or integrated into smartwatches, offer continuous temperature monitoring. They are useful for tracking temperature trends over time, such as during illness or for fertility tracking, but may not be suitable for immediate, highly accurate spot-checks. Recent studies have highlighted their use in monitoring high-risk patients, like those undergoing chemotherapy, for early signs of infection.

Comparison of Thermometer Types


Feature	Digital Oral/Rectal	Infrared Temporal Artery	Infrared Tympanic	Wearable Monitor
Contact	Yes	No	No (Probe touches ear canal)	Yes
Accuracy	Rectal is most accurate for core temp. Oral is reliable for older kids/adults.	Good, but affected by external factors.	Good, but affected by earwax and technique.	Variable; best for trend tracking, not spot-checks.
Speed	10-60 seconds.	1-2 seconds.	2 seconds.	Continuous monitoring.
Best For	Rectal: infants/young children. Oral: older children/adults.	All ages, quick screening.	Infants over 6 months, older children, adults.	Continuous monitoring, sleep tracking, fertility.
Ease of Use	Simple, but requires patient cooperation for oral readings.	Very easy and non-invasive.	Simple, but requires proper aim.	Minimal user effort once applied.

Interpreting Temperature and Its Limitations

For adults, a temperature of 100.4°F (38°C) or higher is generally considered a fever. However, the number alone does not tell the whole story. A fever can indicate a variety of issues, from viral or bacterial infections to chronic conditions or reactions to medication. It is the body's natural defense mechanism, creating a hostile environment for pathogens.

While helpful, temperature checks have significant limitations, especially when used for mass screening. Studies during the COVID-19 pandemic revealed that a large percentage of infected individuals, particularly asymptomatic carriers, did not present with a fever. This led to the conclusion that temperature screening, while providing a sense of security, is an ineffective standalone strategy for preventing disease transmission. Instead, it should be viewed as one piece of a larger puzzle, used in conjunction with other health monitoring and preventive measures like symptom questionnaires.

Best Practices for Accurate Readings

To ensure the most accurate temperature reading, especially with non-contact devices, proper technique is essential. For temporal thermometers, factors like ambient temperature, direct sunlight, and sweat can all interfere. Likewise, earwax can obstruct a tympanic thermometer's reading. Always follow the manufacturer's instructions for the specific device you are using.

For older thermometers, such as the now-deprecated glass mercury versions, it is critical to dispose of them properly due to their toxicity. Modern digital and infrared options offer safer and faster alternatives.

Conclusion

Temperature checks are a simple and effective tool for personal health awareness, allowing you to monitor for signs of illness like fever. While technological advancements have provided quick and convenient options like infrared thermometers, understanding their limitations is crucial. Non-contact devices are excellent for quick screening but should not be relied upon as the sole indicator of health, as many illnesses can occur without a fever. The most accurate readings come from proper technique and using the right thermometer for the situation, such as rectal for infants. Ultimately, observing trends in your personal baseline temperature and seeking medical advice when symptoms are concerning is the most responsible approach to health and wellness. For more detailed medical information, the MedlinePlus Medical Encyclopedia is a useful resource.

Frequently Asked Questions

For adults, a fever is typically defined as a body temperature of 100.4°F (38°C) or higher. However, individual baseline temperatures can vary, so a significant rise above your normal reading can also be a cause for concern.

For infants and young children, a rectal temperature is the most accurate. For older children and adults, oral and temporal artery thermometers can provide reliable readings when used correctly. Armpit readings are the least accurate.

Non-contact infrared thermometers are useful for quick, non-invasive screening but are less accurate than contact methods like rectal or oral measurements. Environmental factors, user technique, and skin conditions like sweat can affect the reading.

No, a temperature check cannot diagnose an illness. A fever is a symptom, not a diagnosis, and can be caused by various conditions. It signals that your body's immune system is active, but a doctor's evaluation is needed for an accurate diagnosis.

To take an accurate oral temperature, place the tip of the thermometer under the tongue towards the back. You must wait at least 15 minutes after eating or drinking anything, and keep your lips sealed around the thermometer until it beeps.

Research has shown that the average human body temperature has been gradually decreasing over time, and many healthy people have a baseline that is naturally lower than the traditional 98.6°F. Factors like age, time of day, and individual physiology also contribute to variations.

Temperature screenings can be ineffective because many people with an infection, including COVID-19, are asymptomatic and may not develop a fever. This is why public health officials recommend combining temperature checks with symptom questionnaires and other safety measures.