Fever - what is it and how can we measure it to prescribe medication?

Fever - what is it and how can we measure it to prescribe medication?

Infectious Diseases

An elevated body temperature is one of the most common symptoms that causes us to feel anxious. We might be even more stressed if our child is feverish. Is every fever dangerous? Find out how to properly measure the temperature and when to administer antipyretics (substances which reduce fever) and at what dosage.

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What is fever?

Fever is our natural defensive reaction against factors that trigger inflammation. It usually appears as a result of intrusions into the body, such as viruses, bacteria, fungi, foreign bodies or allergens - these are so-called external pyrogens. After coming into contact with them, the cells of the immune system start producing their own fever-provoking substances. The internal pyrogens are then created, affecting the thermoregulatory center located in the hypothalamus. They change the biological set point of body temperature to a higher level. Then, our body attempts to adapt intensely to maintain a new, higher temperature, for example when our muscles tremble (often referred to as ‘chills’).

How many degrees is indicative of a fever?

It is generally accepted that the correct temperature of the human body is 36.6 ° C. However, this is not entirely true. The result that we get depends primarily on the place of measurement and the accuracy of the thermometer used. In addition, the temperature of our body undergoes natural daily fluctuations - increasing in the afternoon (16:00 - 18:00) and reducing around 6:00 in the morning. There is also a dependence on activity - crying, anger and physical exertion can be the reason for its increase. Higher temperature is also observed in people using a high protein diet and during ovulation in menstruating women. In healthy people, the normal temperature ranges are:

A temperature exceeding 38.0 - 38.5 °C is reason to be concerned - we are then talking about a fever. However, a temperature ranging from 37.0 to 38.0 °C is a low-grade condition.

How can your temperature be measured?

What thermometer should we choose and where can we measure the temperature? This question has no unequivocal answer, because each of the measurement methods has its pros and cons. The most important thing is to use the same thermometer and the place of measurement throughout the duration of the disease. That way we can exclude any issues as a result of taking temperature readings from varying body parts which may be slightly warmer or colder. The place where the temperature is measured depends on the child's age.

Age Recommended method
from birth to 2 years recommended measurement in the rectum; measurement in the region of the temporal artery or under the armpit (screening)
3-5 years recommended measurement in the ear or mouth; measurement under the armpit or around the temporal artery (screening); measurement in the rectum, if necessary, verification
>5 years recommended measurement in the mouth or ear; measurement under the armpit or around the temporal artery (screening); measurement in the rectum, if necessary, verification;

*axillary - is considered the least accurate point of measurement

When should you "kill" a fever?

An increase in body temperature is a natural defense mechanism of the body. Therefore, temperatures below 38.0 °C (some sources say 38.5 - 39.0 °C) should not be lowered. Remember that a good tolerance of fever is crucial here. If we feel relatively fine, we can refrain from administering antipyretics. The same applies when the fever is affecting your child, if their behaviour is relatively normal, if they have a good appetite and drink a lot, they are probably tolerating the fever quite well. However, if the fever causes suffering such as a headache, then you can take an antipyretic. With children, it’s very important observe their behaviour. If your child is in pain, feeling overworked, is refusing to eat, drink or starts to show additional symptoms indicating an infection (e.g. vomiting) then they should be given an antipyretic.

Antipyretic drugs and their dosage

Paracetamol – it is a painkiller and antipyretic, but has no anti-inflammatory effect.

Ibuprofen – it is a painkiller, antipyretic and anti-inflammatory.

There is a very good calculator of antipyretic syrups on the mamaginekolog.pl website (authored by Alicja Jaczewska and Jakub Wójcicki).

Other antipyretics:


Aspirin = acetylsalicylic acid

Metamizole (pyralgina)

How do you use antipyretics?

  1. Do not use preparations containing combined substances, e.g. paracetamol and ibuprofen in one syrup or tablet. This is important as it can cause vomiting.
  2. If a person with fever vomits after taking an antipyretic drug (e.g., ibuprofen), do not re-administer the same drug because we are not able to estimate how much medicine remained in the stomach and was absorbed. It is then recommended to include a second antipyretic (e.g. paracetamol).
  3. If a person with fever is vomiting or has problems swallowing, consider giving them an antipyretic in the form of suppositories.
  4. The time intervals indicated above concern the next doses of the same drug and should be strictly observed. It is worth noting down the temperature measurement and the time, the name and dose of the administered drug.
  5. If the fever continues, it is worth taking one kind of medicine regularly to maintain its continuity (e.g., paracetamol every 4 hours or ibuprofen every 8 hours).
  6. If one drug is not enough and the fever increases before the next dose of the same drug - in the interval between successive doses of the parent drug (e.g. ibuprofen) you can give the second drug (e.g. paracetamol). It is important to remember to keep the right intervals between each dose of the same drug.

Ways you can fight fever at home

Keep in mind that home remedies do not replace antipyretic drugs and its administration may be necessary with poor fever tolerance.

When should you talk to a doctor?

  1. Interna Szczeklika 2018 Internal Diseases Handbook, Authors: Piotr Gajewski, Andrzej Szczeklik Publisher: Medycyna Praktyczna
  2. E.Kuchar, Body temperature measurement and its interpretation, "Practical Pediatrics Medicine. Common problems in pediatric practice in questions and answers ", special edition 2/2017, p. 15
  3. http://www.mp.pl
  4. https://www.mp.pl/pacjent/
  5. https://www.mp.pl/pytania/pediatria/najnowsze-pytania/178525,jakim-termometrem-mierzyc-temperature-u-dziecka
  6. https://www.mp.pl/pacjent/pediatria/lista/83121,zasada-pomiaru-temperatury-u-dzieci
  7. https://www.mp.pl/pacjent/zapytajlekarza/lista/show.html?id=61427
  8. https://mamaginekolog.pl/goraczka/
  9. https://mamaginekolog.pl/kalkulator-objetosci-syropu-przeciwgoraczkowego/
  10. https://www.mamalekarz.pl/blog/2016/11/24/goraczka-u-dziecka/
  11. https://www.lekarzdladzieci.pl/pediatria/goraczka/
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