Sep 9, 2021
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Mercury, digital, infrared: how to use thermometers correctly

Mercury and galinstane thermometers

A medical mercury thermometer belongs to the maximum thermometers – this means that it shows the maximum temperature value reached during the measurement, and when it decreases, the mercury column does not go down. That is why, before placing the thermometer in the armpit area, you need to shake it well.

Despite the fact that in Western countries they have long preferred to use digital thermometers, in Russia many still use mercury in the old fashioned way, considering them the most reliable. However, this “old-fashioned” way of measuring temperature is gradually becoming a thing of the past: since 2020, Russia, following other WHO countries, has abandoned the production of mercury thermometers. The reason is simple: using mercury-containing appliances at home is too dangerous.

Now, in maximum thermometers, instead of mercury, they use the safe liquid metal galistan (an alloy of gallium, indium and tin). In fact, this is the “brother” of a mercury thermometer, that is, it looks and is used in exactly the same way.

Pros of maximum thermometers:

  • stable measurement accuracy (permissible error of 0.1 degrees);
  • a variety of measurement methods (rectally, orally or armpit);
  • durability (if not dropped, then there is nothing to break in the mercury and galinstan thermometer);
  • ease of disinfection (except perhaps to boil);


  • it is relatively easy to break, and even if you use a galinated thermometer, dangerous small fragments will remain on the floor;
  • significant measurement time – about 10 minutes;
  • it is undesirable for young children to use it orally;
  • A galinstant thermometer freezes at -19 ° C, so it should only be stored at room temperature.

Electronic (digital) thermometer

Today it is the most popular way to measure temperature due to its ease of use and safety. An electronic thermometer in a plastic capsule has a metal tip that changes its electrical conductivity depending on body temperature. These changes are recorded by the device and converted into the usual degrees of Celsius.

There is a widespread myth in Russia that digital thermometers “lie”. According to the doctor and medical blogger Alexei Vodovozov, the explanation for this is very simple: many simply do not read the instructions for the thermometer.

“When using a digital thermometer, people often make the same mistake: they look at the readings immediately after the beep, which actually indicates that the temperature is rising at a certain rate. After the thermometer “squeaked”, it must be held under the arm for at least one more minute. “

A digital thermometer may incorrectly measure body temperature even if it is produced by an uncertified company. To avoid this, it is enough to buy a thermometer at a pharmacy, and not at Aliexpress.

Pluses of an electronic thermometer:

  • safety: such a thermometer cannot be broken, there is no mercury and glass in it;
  • measurement time is about 1.5-3 minutes;
  • ease of reading the results;
  • automatic shutdown;
  • almost all models remember the last readings;
  • backlit thermometers can be used in the dark.


  • changing batteries may be required at the most inopportune moment.

Infrared (ear) thermometer

This thermometer measures the temperature inside the ear by reading infrared radiation. The device appeared on the market relatively recently and is in great demand due to the fact that it allows you to quickly and without direct contact measure body temperature, including a child or a sleeping person. Like an electronic thermometer, it is completely safe. But despite its convenience, such a device has serious limitations.

Pros of an infrared thermometer:

  • equipped with all the additional functions of electronic thermometers (memory, sound signals, auto shutdown, etc.);
  • makes it possible to very quickly measure the temperature (5-30 seconds);
  • replaceable tips solve the issue of hygiene and disinfection.


  • if the device is incorrectly calibrated, its accuracy can be significantly reduced;
  • also gives unreliable results if a lot of sulfur has accumulated in the ear or there is inflammation;
  • not suitable for children under 6 months of age due to developmental peculiarities;

  • can be used no earlier than 15 minutes after returning from the street, especially in winter;
  • quite high cost: the price tag is from 500 rubles, a high-quality model will cost 3-4 times more.

Thermal strips… It is a heat-sensitive film, the appearance of which changes depending on the temperature of the body to which it is applied. They have only a gradation of “increased” or “not increased”, indicating only whether it is necessary to measure the temperature in another way. Such a thermometer can be used only in field conditions, when it is not possible to use a normal thermometer.

Nipple thermometers… They are often used for babies, but alas, they are not very accurate. In addition, in order to measure the temperature, they must be in the mouth for a fairly long time.

How to measure the temperature in the armpit

For this method of measuring temperature, a mercury, galinated or electronic thermometer is suitable.

  • if you’ve recently eaten or been exercising, wait at least 30 minutes.
  • the glass thermometer must be shaken so that the temperature on the column is at least 35 ° C. If the thermometer is electronic, just turn it on.
  • the armpit should be dry, sweat should be wiped off with a napkin or towel.
  • keep your hand firmly against your body, this is necessary to heat the skin under the armpit so that it coincides with body temperature.
  • the maximum thermometers should be kept up to 10 minutes, the electronic thermometer – a minute longer after the beep.

How to measure temperature rectally

Usually this method is used to determine the temperature in babies, and only an electronic thermometer is suitable for this, since a glass thermometer is too unsafe.

  • to measure rectal temperature, get a separate thermometer that you will not use in other ways;
  • wash the thermometer with warm water and soap;
  • Apply a small amount of petroleum jelly or other lubricant to the tip;
  • lay the child on his side or back, bend his legs.
  • gently insert the thermometer into the anus until its tip fully enters the rectum;
  • after use, thoroughly wash the thermometer with soap and wipe it with an alcohol antiseptic.

How to measure temperature orally

This is the most common way to measure temperature in Western countries, as it is considered more accurate than measuring it in the armpit. You can use either a glass thermometer or a digital thermometer to determine the temperature in your mouth, but for safety reasons it is better to use the latter.

  • Wash your hands with soap, then rinse the thermometer in cold water and wipe it with an antiseptic. Remove the remaining alcohol with a clean dry cloth;
  • After eating or drinking, you should wait 30 minutes before taking the temperature so that the readings are correct.
  • Place the tip of a thermometer – maximum or digital – under your tongue and hold it as long as necessary for the type of thermometer.

How to measure the temperature in the ear

  • Carefully place the switched on device into the ear canal no further than indicated in the instructions;
  • Hold the thermometer firmly until you hear a beep.

The most optimal body temperature for an adult is 36.6 ° C, and it is considered normal up to 37 ° C. It is usually lowered in the morning and peaks in the afternoon or late afternoon. There are also individual characteristics: for example, for some people 37.2 ° C may be the “working” temperature.

In children under one year old, rectal temperature can rise to 37.7 ° C (36.5–37.1 ° C under the arm), and this is also the norm.

There is an important nuance: the temperature in the mouth is higher than under the arm by 0.3–0.6 ° C, the rectal temperature is by 0.6–1.2 ° C, in the ear – up to 1.2 ° C. Thus, 37.5 ° C is a cause for concern if you have measured the temperature in the armpit, but not rectally.

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