Using a Clinical Thermometer: 9 Steps (with Pictures)

Table of contents:

Using a Clinical Thermometer: 9 Steps (with Pictures)
Using a Clinical Thermometer: 9 Steps (with Pictures)

Fever is a result of a rise in your body temperature. Mild fever is often beneficial because it indicates that the body is trying to defend itself against infection. Many disease-causing (pathogenic) microorganisms thrive within a narrow temperature range, so a mild fever prevents them from reproducing. However, some fevers may be related to connective tissue disorders or a serious illness. High fevers (of 39.4°C or higher for an adult) are potentially dangerous and should be monitored closely using a thermometer. There are many types and models of thermometers intended for different areas of the body. The most appropriate choice is usually determined by the age of the person with the fever -- for example, some thermometers are more appropriate for small children. Once you have chosen the most suitable thermometer, using it is relatively easy.


Part 1 of 2: Selecting the most suitable thermometer

Use a Thermometer Step 1
Use a Thermometer Step 1

Step 1. Take rectal temperature readings in newborns

The best or most appropriate type of thermometer and where to measure body temperature depends primarily on age. From birth to about six months of age, the use of a regular digital thermometer for a rectal (anal) temperature reading is recommended as it is considered the most accurate.

  • Earwax, ear infections and small, curved ear canals hinder the accuracy of ear thermometers, so they are not the best types to use on newborns.
  • There is research that would suggest that temporal artery infrared thermometers are also good options for newborns because of their accuracy and reproducibility. The temporal artery can be seen at the temples of the head.
  • The American Academy of Pediatrics does not recommend using old-fashioned glass thermometers that contain mercury. The glass can break and mercury is toxic to humans, so digital thermometers are safer options.
Use a Thermometer Step 2
Use a Thermometer Step 2

Step 2. Choose carefully where you take the temperature for toddlers

Up to about three years of age (and perhaps as many as five years), a rectal reading with a digital thermometer still provides the most accurate record of the body's core temperature. You can use a digital ear thermometer at a younger age to get general readings (better than no temperature at all), but until about age three, readings from the rectal, axillary, and temporal arteries are considered more accurate. Because mild to moderate fevers are more dangerous in toddlers than adults, accurate temperature readings during early childhood are especially important.

  • Ear infections are common, especially in newborns and toddlers, affecting the readings of infrared ear thermometers. That is why ear thermometers usually give too high values for ear infections.
  • Common digital thermometers are quite versatile and can record temperatures through the mouth (under the tongue), armpit or rectum and are suitable for use on newborns, toddlers, older children and adults.
Use a Thermometer Step 3
Use a Thermometer Step 3

Step 3. Choose a thermometer and measure each area for older children and adults

Children over three to five years old tend to get less ear infections, and it's much easier to clean their ears and remove earwax. Earwax in the ear canal hinders an accurate perception by an ear thermometer of the infrared radiation coming from the eardrum. In addition, children's ear canals grow and eventually become less curved. Consequently, after the age of three to five, all types of thermometers used in most areas of the body will be about equally accurate.

  • Digital ear thermometers are often considered the fastest, easiest and cleanest way to measure body temperatures.
  • Using a regular digital thermometer rectally is very accurate, but probably the most unpleasant and inconvenient way to determine body temperature.
  • Heat-sensitive strips that are applied to the forehead are convenient and affordable, but not as accurate or accurate as digital thermometers.
  • There are also "forehead thermometers" that are different from plastic strip thermometers. These are more expensive, usually used in the hospital, and use infrared technology to obtain readings in the temporal region.

Part 2 of 2: Using different thermometers

Use a Thermometer Step 4
Use a Thermometer Step 4

Step 1. Use a digital thermometer orally

The mouth (oral cavity) is considered a reliable representation of body temperature when the thermometer is placed far back under the tongue. Remove the digital thermometer from the holder and turn it on; slide the metal tip into a new disposable plastic sleeve (if available); place it back under the tongue as far as possible; Gently close your lips around the thermometer until it beeps and reads. It may take a few minutes, so breathe slowly through your nose while waiting.

  • If you don't have a disposable sleeve, clean the metal end with soap and warm water (or alcohol), then rinse with cold water.
  • Wait 20-30 minutes after smoking, eating or drinking hot/cold liquids before taking oral body temperature measurements.
  • Human core temperatures average around 37°C (although it varies due to many factors), but oral temperatures taken with a digital thermometer tend to be slightly lower, with an average reading of 36.8°C.
Use a Thermometer Step 5
Use a Thermometer Step 5

Step 2. Use a digital thermometer rectally

A rectal temperature reading is usually only intended for toddlers, preschoolers and newborns, but it is also very accurate for adults, although it may be a bit uncomfortable. Before inserting a digital thermometer into the anus, you must first apply some sort of jelly, water-soluble or petroleum-based. The lubricant is usually placed over the tip shell -- it is then easier to insert and a little more comfortable. Spread the buttocks (it is easier if the patient is on the stomach) and place the end of the thermometer no more than an inch into the rectum. Never force the thermometer if resistance is encountered. Wait a minute or more for the thermometer beep, then remove it slowly.

  • Be especially thorough when cleaning your hands and the thermometer after taking a rectal shot, as E. coli bacteria from fecal material can cause serious infections.
  • For rectal recordings, consider buying a digital thermometer with a fairly flexible tip at the end, as it provides more comfort.
  • Rectal readings with a digital thermometer can be up to one degree higher than oral and axillary readings.
Use a Thermometer Step 6
Use a Thermometer Step 6

Step 3. Use a digital thermometer under the arms

The armpit is another place to measure body temperature, although it's not considered as accurate as the mouth, rectum, or ear (tympanic membrane). After placing a sleeve over the metal end of the digital thermometer, make sure the armpit is dry before inserting the thermometer. Place the tip of the thermometer in the center of the armpit (pointing up at the head), then make sure the arm is close to the body so that the body heat is trapped. Wait at least a few minutes or until the thermometer beeps before taking the temperature.

  • Wait at least an hour after strenuous exercise or a warm bath before taking body temperature from the armpit or elsewhere.
  • For more accuracy, take images of both armpits and then calculate the average of the two temperatures.
  • Underarm readings with a digital thermometer tend to be lower than other areas, with an average normal temperature around 36.5°C.
Use a Thermometer Step 7
Use a Thermometer Step 7

Step 4. Use an ear thermometer

An ear thermometer has a different shape than a normal digital thermometer because it is specially designed to fit into the ear canal. Ear thermometers record infrared radiation from the eardrum. Before inserting the thermometer into the ear canal, make sure it is free of wax and dry. Earwax and other debris in the ear canal reduces the accuracy of recordings. After turning on the ear thermometer and placing a sterile sheath on the cap, hold the person's head still and pull the top part of the ear back to straighten the canal and make it easier to insert the thermometer to bring in. It is not the intention to touch the eardrum with the tip, as the thermometer is designed to be read from a distance. After creating a seal around the thermometer by pressing it against the channel, wait for the beep to indicate a reading.

  • The safest and most effective way to clean ears is to use a few drops of warm olive oil, almond oil, mineral oil or special ear drops to soften the earwax, then rinse (rinse) everything out with a little water from a small rubber device made for cleaning the ear. Cleaning the ears is easiest if done after a shower or bath.
  • Do not use an ear thermometer on an ear that is infected, injured, or recovering from surgery.
  • An advantage of using an ear thermometer is that, if properly placed, it is fast and quite accurate.
  • Ear thermometers are generally more expensive than regular digital thermometers, but their price has dropped significantly in the last decade.
Use a Thermometer Step 8
Use a Thermometer Step 8

Step 5. Use a plastic strip thermometer

Strip thermometers are held to the forehead and are relatively popular for taking children's temperatures, but they are quite variable in their accuracy. These thermometers use liquid crystals that change color in response to heat to indicate the temperature of the skin (but not that of the body). Strip thermometers are usually taped (horizontally) to the forehead and must be left in place for at least a minute before they can be read. Before applying, make sure there is no sweat on the forehead from physical activity or that the skin is severely sunburned -- both situations will affect the reading.

  • It is difficult to get measurements to 1/10 of a degree because the liquid crystals have a certain temperature range when they change color.
  • For more accuracy, place the strip closer to the temples of the head (over the pulsating temporal artery near the hairline). The blood in the temples is closer in temperature to the internal temperature of the body.
Use a Thermometer Step 9
Use a Thermometer Step 9

Step 6. Learn how to interpret the recordings

Keep in mind that newborns have a lower body temperature than adults -- usually below 36.1°C, compared to 37°C for adults. Thus, a temperature reading indicating a mild adult fever (37.8°C, for example) could be more serious for a baby or child. In addition, the different types of thermometers have slightly different normal ranges because they measure body heat in different places. For example, your child has a fever on a rectal or hearing temperature reading of 38°C or higher, an oral reading of 37.8°C or greater, and/or an axillary reading of 37.2°C or greater.

  • In any case, contact your doctor if your child three months or younger has a rectal temperature of 38°C or higher, your child from three to six months old has a rectal or ear temperature above 38.9°C, your child from 6 to 24 months old has a temperature of more than 38.9°C, which lasts for more than a day, regardless of the thermometer.
  • Most healthy adults can tolerate a fever of 39-40°C for short periods without any problems. However, a temperature of 41-43°C (called hyperpyrexia) is serious and requires medical attention. Temperatures above 43°C are almost always fatal.


  • Carefully read the instructions for use supplied with the thermometer. While most digital thermometers generally work the same way, you want to make sure you understand how to best use your particular instrument.
  • Prepare the thermometer for reading the temperatures by pressing the button to turn it on -- but make sure the reading is at zero before sliding the disposable plastic sleeve over the metal tip.
  • Cases for digital thermometers are available everywhere that sells thermometers (grocery stores, pharmacies, etc.) They are inexpensive and usually fit any device.
  • Babies can't regulate their body temperature well when they are sick, and they may get colder instead of warmer and feverish.
  • If you have had a hot or cold drink, wait about 15 minutes before taking your temperature.


  • An ear temperature of 38°C or higher is a fever, but if your child is over one year old and drinks plenty of fluids, is playful and sleeps normally, there is usually no reason or need to treat it.
  • Temperatures of 38.9°C and above combined with symptoms such as unusual irritability, discomfort, lethargy and moderate coughing and/or diarrhea do warrant a visit to the doctor.
  • Symptoms of a high fever (39°C or higher) are often accompanied by hallucinations, confusion, severe irritability, and convulsions -- they are considered medical emergencies and you should seek emergency care immediately.

Popular by topic