When do you have a fever? questions and answers

Wann hat man Fieber? Fragen und Antworten

Knowing when you have a fever is more important and interesting than ever these days. Due to the corona pandemic, the topic of fever has once again increased significantly. Because one of the most important symptoms of Corona is fever and cough. But at what temperature do you actually have a fever? And is my measuring instrument the right one? What other symptoms can fever have? We clarify these and other questions in this report.

Fever is a typical feature of many infections. It serves as a protective mechanism for the human body. In this article we would like to give you clarity on the topic of when you have a fever. We took a closer look at various scientifically based reports and articles and want to provide you with reporting that is as neutral as possible. This should answer all your questions about this topic.

the essentials in brief

  • Fever is a protective reaction of the body and not a disease in its own right. It is a condition of the body in which the body temperature is permanently elevated. It shows itself through symptoms such as cool skin, feeling cold, shaking or even chills. Normally, after the infection has been defeated, the temperature will return to its original level on its own.
  • Fever can be measured in a number of ways. The most reliable way is to take the temperature rectally. Other methods include measurements in the ear, on the forehead, under the arm, or in the mouth.
  • You have a slight fever if the temperature is above 38.1 degrees Celsius. One speaks of an elevated temperature from 37.5 degrees Celsius. Moderate fever starts at 38.6 degrees Celsius, high fever at 39.1 degrees Celsius and very high fever at 40.0 degrees Celsius. These readings are especially true for a rectal measurement.

When do you have a fever: What you should know

Fever is not a disease in its own right, but rather a symptom of disease. It is a protective reaction of the body to various diseases. Elevated temperatures are said to help the body fight a specific infection. But when do you actually have a fever and what are the symptoms?

Fever is not a disease in itself, but a symptom of it.

We have tried to answer your questions about "when do you have a fever" in detail and precisely using scientific articles. We also go into the different temperature intervals and explain the differences between children and adults. Of course, we will also explain the individual measurement methods and which one is the most accurate. At certain temperatures you should also consult a doctor.

Teddy bear with thermometer, mask and handkerchief

If you have a fever, you should rest and drink plenty of fluids. (Image source: Myriam Zilles / unsplash)

what is fever

Fever is a protective reaction of the body and not a disease in its own right. It is a condition of the body in which the body temperature is permanently elevated. The increase in temperature accelerates metabolic processes and mobilizes the defense mechanisms. In the case of certain pathogens, such as a cold, the body has a higher need for heat, which is controlled by the brain. That's why you tremble when you have a fever to promote heat production.(1,2)

Fever is manifested by symptoms such as cool skin, chills, tremors or even chills. After an infection has been successfully combated, body temperature usually returns to its original level on its own. (1,2)

However, you should note that your body temperature is not constant and that daily fluctuations are normal to a certain extent. In addition, the respective measured body temperature also depends on the measuring location. Measurements in the rectal area are higher than measurements in the mouth. Fluctuations in temperature are also normal during the female cycle. After ovulation, the woman's body temperature increases by around 0.5 degrees Celsius. (11)

When do you have a fever?

You have a fever from a body temperature of 37.8 degrees Celsius, when measured orally. Our table shows the values ​​for a rectal measurement. With this type of measurement, you have a fever if the temperature is above 38.1 degrees Celsius. In general, it can be said that the values ​​are always lower with an oral measurement. One speaks of an elevated temperature from 37.5 degrees Celsius. Moderate fever starts at 38.6 degrees Celsius, high fever at 39.1 degrees Celsius and very high fever at 40.0 degrees Celsius.

The table below shows the individual temperature ranges that you can use as a guide when taking a temperature measurement.

interval temperature
Normal temperature 36.5°C - 37.4°C
High temperature 37.5°C - 38.0°C
Light fever 38.1°C - 38.5°C
moderate fever 38.6°C - 39.0°C
High fever 39.1°C - 39.9°C
Very high fever 40.0°C - 42.0°C

(1)

Only values ​​from 39 degrees Celsius are really questionable and should be monitored more closely. If you have a fever, it is important that you drink enough and rest. As a rule of thumb, for every degree of fever over 37 degrees Celsius, you should drink half a liter to a liter more. Calf wraps or paracetamol can also help to reduce the fever more quickly. (9)

For calf wraps, take a towel and soak it in cold tap water. It is then wrapped around the outstretched leg. Use the calf wrap for 5 minutes and repeat 2 to 3 times a day. To prevent fever, you can strengthen your immune system . (9)

How do you recognize fever in adults?

If adults have a fever, it is usually harmless. In the case of illnesses such as the flu or a cold, it is a natural defense reaction of the human body. From temperatures of 38.1 degrees Celsius, an adult has a slight fever. A doctor's visit is only recommended if the temperature exceeds 39 degrees Celsius and lasts for more than two days. (1)

There are several other signs and symptoms that you can use to tell if you have a fever. At first, the body may feel tired, listless or battered. Some people also have joint or limb pain. The severity of the symptoms does not necessarily depend on the temperature level of the fever. (5)

Other typical features of fever are:

  • Sweats , thirst
  • Dry and hot skin, shiny eyes
  • coated and dry tongue
  • chills
  • loss of appetite
  • nausea, vomiting
  • constipation
  • rapid breathing rate
  • restlessness, confusion, hallucinations (5)

There are various causes of fever, which will also tell you whether you have an elevated temperature or not. Diseases that cause a slight fever can be infections, pelvic inflammatory disease, heart valve inflammation, tuberculosis, inflammation of the blood vessels and a number of other diseases. (10)

At temperatures above 38.5 degrees Celsius, diseases such as infections, tumors, diseases of the connective tissue, rheumatological diseases or Crohn's disease can be the cause of fever. A high fever can therefore be a sign of a serious illness. Therefore, if you have a persistent high fever, you should always consult your doctor as a precaution. (10)

How to recognize fever in children?

In children, you should be particularly careful with many illnesses, including fever. Here, going to the doctor is recommended faster than for adults. The table below shows which temperatures are normal in children and which ones it is better to consult a doctor. We have also formulated a few tips on what parents can do at which temperature.

interval temperature What can parents do
Normal temperature from 36.5°C Diurnal fluctuations possible, often higher in the evening than in the morning, movement or warm clothing can increase the temperature
High temperature from 37.5°C Observe the child carefully, let the child drink every half hour, check the temperature regularly, if the child is fit no further measures are necessary
Fever from 38.5°C Observe the child carefully, bed rest, let the child drink every half hour, check the temperature regularly, to be on the safe side consult the pediatrician
High fever from 39.1°C Pay particular attention to the child, rest in bed, let the child drink every half hour, offer easily digestible food, check the temperature regularly, do not wrap the child too warmly, consult a pediatrician, possibly wrap around the abdomen or calves

(4)

In general, a visit to the doctor is recommended for infants under the age of three months when their temperature reaches 38 degrees Celsius. Temperature fluctuations are normal, especially in the first few months. When in doubt, it is always better to ask a pediatrician. This is primarily a precautionary measure. Infants under the age of two should be taken to the doctor by their parents if the fever lasts more than a day. (3.4)

Temperature measurement in children with an ear thermometer

Taking fever in children with an ear thermometer (Image source: Kelly Sikkema /unsplash)

For older children, a doctor's visit is recommended from a fever of 39 degrees Celsius. In particular, cases that last longer than two days or occur repeatedly should be observed. It is important that the child rests with an elevated temperature and stays mainly in bed until improvement. Check your child's temperature regularly and make sure they are drinking enough. At higher temperatures, easily digestible foods are also recommended. (3.4)

How is fever measured correctly?

Depending on where a person measures their temperature when a fever is suspected, different temperatures come out. The most reliable measurements are with a digital thermometer in the bottom (rectal) or in the ear. (7)

Fever can be measured in the buttocks, mouth, ear, forehead and armpits.

Especially in children, a rectal measurement makes the most sense, as the results are the safest and most accurate. When measuring under the tongue or on the forehead, the results are about 0.4 degrees Celsius too low. If you measure under the armpit, you get a value that is up to 0.6 degrees Celsius lower. You should definitely take this into account when measuring! (7)

The individual measuring methods and their correct application:

  • Measurement in the bottom: This type is not particularly popular, but it is very accurate. In order to get an optimal result and to make the measurement as comfortable as possible, you should grease the tip of the thermometer with a suitable cream and lie on your side or back.
  • Measurement in the mouth: With this method, you should note that you should not drink anything hot or cold about 30 minutes before the measurement. Otherwise this would falsify the result. The tip of the thermometer is placed under the tongue and the lips should be closed. If the measurement is performed correctly, this method is relatively reliable.
  • Measurement in the ear: Before using the device, read the accompanying instructions for use. During the measurement, the ears must be pulled back and up slightly in order to expose the auditory canal. With children, it should be noted that it must not be on their ear beforehand, otherwise the result will be falsified. Compared to the rectal measurement, the temperature with eardrum measurements is about 0.3 to 0.5 degrees lower.
  • Measurement on the forehead: This method is very simple and convenient, but also inaccurate. Since the measurement takes place at the temple, the temperature of children can also be measured while they are sleeping.
  • Measurement under the armpit: This measurement method is very imprecise. A measurement time of at least five minutes should be observed. The temperature can vary from 0.6 to 2 degrees from a rectal measurement. (7.8)

It is up to you which type of measurement you prefer. Please note, however, that the temperatures can be different and that a result can also be partially falsified. Use a thermometer that is comfortable for you or your children. If you suspect you have a fever, you should measure your temperature several times a day. If you are unsure which method is right for you, you can always ask your doctor or pharmacist. They will certainly be happy to help you with words and deeds.

At what temperature is fever dangerous?

Fever becomes dangerous at a temperature of over 39.5 degrees Celsius for several days. If, on the other hand, you have a cold or another infection, the temperature usually normalizes itself. This can take a few days. However, if your temperature rises above 40.0 degrees Celsius, you should consult a doctor as soon as possible. The high temperature can be dangerous for the body.

In addition, values ​​above 40.0 degrees Celsius are usually a sign of a more serious illness, as the body tries to heal itself with the fever. In addition, if you have a high fever, there is a risk of dehydration or cardiovascular problems, which is particularly the case in older people. Dizziness or other disorders of the nervous system are also possible. (1.3)

With small children, you should consult a doctor as a precaution from 38 degrees Celsius. Children always have infections and other diseases that can be a cause of fever. The pediatrician can treat the disease quickly or recommend appropriate anti-fever remedies and measures to the parents. Better safe than sorry in this case.

Conclusion

We tried to clear your doubts about when you have a fever. It's important to pay attention to your body's symptoms. In addition to an elevated temperature of 38.1 degrees Celsius, sweating, shiny eyes, chills or nausea can be signs of a fever. Especially during the current corona pandemic, it is very important to pay attention to these symptoms.

If you have a fever, you should stay at home at the moment and do a corona test. Apart from Corona, fever is often not dangerous and usually goes away on its own after a few days. You should only see a doctor as soon as possible if the temperature is above 40.0 degrees Celsius. Temperatures below this value, on the other hand, are only critical over a longer period of time. If in doubt, you should always consult your doctor. Children also need to be more careful than adults.

There are different measuring methods that differ in accuracy and result in different measuring temperatures. The most accurate are rectal measurements. If you prefer a different method, be sure to factor in temperature fluctuations. By paying attention to the symptoms and using the correct method to take your temperature, you will quickly know whether you have a fever or not.

References

  1. practicallyarzt.de: Fever: All information at a glance, Moritz Klenk, March 25th, 2021 Source
  2. stiftung-gesundheitswissen.de: fever: background, Dr. Beate Weikert, Dr. Miriam Wiese-Posselt, Prof. Dr. medical Petra Gastmeier, 02/03/2021 Source
  3. apotheken-umschau.de: fever - what the symptom means, Dr. Med. Claudia Osthoff, April 23, 2019 Source
  4. kindergesundheit-info.de: Fever in babies and children, BZgA, April 1st, 2021 Source
  5. internisten-im-netz.de: Fever: Signs & Symptoms, Professional Association of German Internists e. V., 04/01/2021 Source
  6. bene-arzneimittel.de: How do I measure fever correctly?, April 1st, 2021 Source
  7. apotheken-umschau.de: Measure fever correctly: That's how it works, Saskia Dittrich, April 6th, 2020 Source
  8. practicallyarzt.de: Measure fever, Claudia Lapier, 07.04.2020 Source
  9. internisten-im-netz.de: Tips for fever, Professional Association of German Internists e. V., 4/4/2021 Source
  10. internisten-im-netz.de: Fever: causes & risk factors, Professional Association of German Internists e. V., 4/4/2021 Source
  11. internisten-im-netz.de: What is a fever?, Professional Association of German Internists e. V., 4/4/2021Source
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Das war wirklich ein toller Artikel. Danke für den Informationsaustausch. Fahren Sie damit fort.

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