Home Immune systemFever Why does the fever rise higher at night

Why does the fever rise higher at night

by Alivia Nyhan
Published: Last Updated on

Fever is a reaction of the body to possible diseases or infections, in which the body temperature increases to deal with bacteria, viruses, or germs that attack our immune system.

It is a common and common symptom in many diseases, and the majority of the population has suffered from this situation throughout their lives. Depending on whether the body temperature increases significantly, we will talk about the fever being higher or lower, or perhaps a low-grade fever. In the case of having a high fever for long periods, we advise visiting your doctor.

On the other hand, the increase in temperature can grow throughout the day. So in this FastlyHealarticle, we will know why the fever rises more at night.

When is fever considered?

fever is the body temperature elevated utilizing parameters established. Following these characteristics, we can talk about:

  • febrile or tenths when the person is between 37.5ºC and 38ºC.
  • Low fever , 38’1ºC and 38’5ºC.
  • Moderate fever , 38.6ºC and 39ºC.
  • High fever, from 39’1ºC.

These parameters are general and are based on the average temperature of people, which is considered to be between 36.5ºC and 37ºC. It can be adapted to each case since there are people who tend to have the lowest body temperature, and therefore, with temperatures that are not so high, they can be in a situation of high fever. For example, a person usually at 34ºC could have a high fever of 37.5ºC.

We must pay special attention to high fever, significantly if it exceeds 40ºC or if the fever lasts for a long time. In these cases, we must go to our doctor to explore the possible causes of this symptom.

Causes of fever

The causes can be very diverse and varied, from a cold to a gastrointestinal infection can cause it. Here are the most common:

Common infection

Germs, bacteria, or viruses that create colds, flu, or various infections, gastrointestinal or in the ophthalmological area, such as tonsillitis, laryngitis, or otitis. In these cases, the fever usually lasts between 24 and 48 hours. It is accompanied by other symptoms that typically affect the specific area where the infection is: stomach pain, ear pain, throat pain, etc.

Severe infections

Caused by bacteria or viruses. Examples of this type are:

Other diseases require medical intervention. In these cases, the fever is usually high, lasts more than 48 hours, and is accompanied by other pain.


Being exposed to sunlight for many hours without protection can lead to an increase in fever. Our body has received too much heat and sunlight, and as a reaction, it generates an increase in temperature that generally occurs at night. It is usually accompanied by intestinal pain and general discomfort.

Hormonal cycle

Many women see their body temperature increase on certain days of their cycle, just after ovulation. In these cases, the fever is usually moderate and does not cause discomfort.

Why the fever rises at night

What is certain is that our body temperature changes throughout the day and that fever can visibly increase at night. The reasons why this happens are as follows:

Body temperature is changing.

It follows the circadian rhythm, that is, the body’s natural rhythm to adapt to the different states and stimuli it receives. Throughout the day, naturally, our temperature changes to adapt to the needs of our system. Thus, in the early morning, our body is usually at lower temperatures, while between 10 and 12, it is at its maximum level. The hypothalamus, the body temperature regulating organ, calculates the temperature of the gland and that of the skin to maintain a balance and generates these cyclical changes. It is usual for our temperature to rise at night, and it does not mean that we are sicker, but instead that it is a chronic and daily reaction of the body.

The health problem worsens.

When our body has been fighting against an external agent for hours and cannot fight it, our health problem worsens, and the body temperature increases to generate more defenses against it.


Having a fever supposes a substantial energy expenditure for our body since it constantly works to eliminate the problem. When night comes, it is expected that our body is tired, and the body temperature rises as its reaction to continue working against the disease.

Poor ventilation or too much heat

Another aspect that can cause our temperature to increase is the excess heat in the area since when we have a fever, we mistakenly think that we should cover ourselves with blankets and that the air does not touch us. These actions increase body temperature as we retain heat. It is essential to ventilate the room and not cover ourselves too much.

We must remind you that it is essential that you go to your doctor if the high fever lasts more than 48 hours or if it rises to more than 40ºC.

This article is merely informative. At FastlyHeal .com, we do not have the power to prescribe medical treatments or make any diagnosis. We invite you to see a doctor if you present any condition or discomfort.

If you want to read more articles similar to Why does fever rise more at night, we recommend that you enter our Immune system category.

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