Methods of Taking Body Temperature

As a vital sign, body temperature helps medical professionals determine if a patient is experiencing any health problems. All vital signs—body temperature, pulse rate, respiration rate, and blood pressure—can be measured in the hospital, at home, or any place where proper equipment is available. The thermometer, a device we are introduced to as infants and use again and again for the rest of our lives, is an indispensable part of our households for this reason.

What is body temperature?

Body temperature is a measure of the body’s ability to generate and eliminate heat. No matter the weather, the human body should be able to keep its temperature within a considerably normal range. A body temperature that is too high or too low can be indicative of a potential health concern.

Of course, what is considered normal for one person may not be normal for the next person. Any given person’s body temperature can also change throughout the day and throughout their lifetime. Some factors that may affect body temperature include the time of day, age, gender, how active the person is, and, for women specifically, the stage of her menstrual cycle.

The body temperature can also change depending on where it is measured on the body. For instance, a thermometer placed in one’s mouth would likely produce lower readings than a body temperature reading via the rectum.

What is a normal body temperature?

A body temperature between 97 F to 99 F is considered normal for adults, while babies and children usually have higher temperatures of up to 100.4 F. A higher temperature reading than normal is considered a fever, and a lower temperature reading than normal can be considered hypothermia.

Ways to take your temperature

1. Oral

A person’s temperature can be taken by inserting a thermometer in the mouth and placing either in the cheek or under the tongue. Placing the thermometer under the tongue is the preferred and recommended method. Younger children may have a difficult time holding the thermometer in their mouth for a set period, so this method is not recommended for young children, such as those under the age of four. However, for older children and adults of all ages, oral thermometers are most often used as a minimally-invasive method of taking temperature. One negative of oral temperature readings is that taking a temperature within 15 minutes of eating or drinking any substance may result in a false reading.

2. Rectal

Rectal temperature is viewed as the gold standard for recording temperature among infants. Taking temperature rectally, most often on newborns and young children, is usually 0.5 to 0.7 F higher than oral temperature, but potentially easier to perform. To obtain a baby’s rectal temperature, cover the tip of the thermometer with petroleum jelly, place the child on their back with their knees bent, and insert the thermometer about an inch into their rectum. It is important to ask the child’s doctor or pediatrician for detailed instructions on taking a rectal temperature, and that the thermometer used for rectal readings is never used orally.

For parents who have a difficult time checking their children’s temperature rectally may use pacifier thermometers as an alternative, although pacifier thermometers tend to be less accurate. Furthermore, the child must leave the pacifier thermometer in their mouth for several minutes, much longer than the other temperature reading methods.

3. Tympanic (Ear)

A tympanic thermometer works by reading the infrared heat in the ear. It is quick to use, which makes it another appealing option for parents who want to measure their children’s temperature. However, it can still produce incorrect readings if it is not used properly or if the child has too much earwax. Tympanic thermometers also should not be used if one is suffering from an earache.

4. Axillary (Armpit)

Temperatures taken under the arm are often 0.3 to 0.4 F lower than oral temperatures and are also lower than temperatures taken rectally. Taking an axillary temperature is as easy as keeping the thermometer under the armpit for a few minutes. However, professionals view axillary readings as inaccurate because the axillary temperature can be affected by perspiration and environmental temperature.

5. Skin

Temporal artery thermometers have become popular in recent years in the form of forehead thermometers. These thermometers can measure the temperature of the skin on the forehead by using an infrared scanner pointed towards the forehead’s temporal artery. Parts of the body that contain arteries, which receive blood directly from the heart, are generally good spots to detect the body’s core temperature. Temporal artery thermometers offer a non-touch method that ensures infection control, but this same advantage allows for criticism that it may not be accurate.

Another option for skin-based temperature readings is through plastic strip thermometers. Available in both disposable and reusable format, these thermometers use color-changing, heat-sensitive liquid crystals to indicate temperature. However, these are seen as inaccurate since they are simply taking the temperature of the skin itself, which is not indicative of the internal body temperature.

6. Vaginal

Women who want to keep track of ovulation cycles can regularly check their basal body temperature, the temperature when the body is at rest, through the vagina. A woman’s temperature rises when she is ovulating, and her temperature stays elevated for around 10 days. She would be most fertile just two or three days before this change in temperature. Tracking basal body temperature could help women who want to conceive or want to avoid pregnancy.

The most accurate

It may be time-consuming and feel uncomfortable, but the rectal temperature still offers the most accurate and reliable temperature reading, as it provides the closest reach into the body to retrieve a core temperature value. However, according to Harvard Health Publishing, many hospitals no longer take rectal temperatures because, aside from patient discomfort, there is a possibility of spreading infectious disease. If it is necessary to take someone’s rectal temperature, it is critically important to make sure the thermometer is labeled as a rectal thermometer and is cleaned regularly. Otherwise, oral thermometers provide the next best option for accuracy and ease of use.