"Fever is a cost to the body, increasing oxygen consumption and caloric and fluid requirements".


The body maintains a constant temperature through a center, called a thermoregulator, located in a part of the brain called the hypothalamus. When that center, for different reasons, sets a higher temperature, fever occurs.

Usually the temperature is somewhat lower early in the day, around 6 a.m., and reaches its maximum between 4 and 6 p.m. At those hours, temperatures of up to 37.7 degrees can be perfectly normal.

We talk about feverish if the fever is low (less than 38º C) and fever if it exceeds 38º C.

Very high fever or accompanied by very pronounced symptoms must be treated. Also in cases of febrile seizures in children, pregnant women, or patients with significant cardiac, pulmonary or cerebral alteration.

However, it does not seem so clear that mild or moderate fever needs to be removed, and in many cases it can hide important information for the diagnosis. 

What are the symptoms of a fever?

They are non-specific symptoms, very variable from one person to another, and also different according to the disease that causes the fever.

The most common are headache, generalized muscle pain, or more localized in the lumbar region, joint pain and drowsiness. The chills occur during the ascent of the temperature, and are the reflection of the increase of muscular activity that the thermoregulatory center orders to increase the corporal temperature.

Irritability or delirium appears more frequently in older people, while febrile seizures are typical of children under five.

The most common symptoms are:

  • Headache.
  • Muscular pains.
  • Drowsiness.
  • Chills.

Do you have a fever or low-grade fever?

A study of the origin of the fever may be necessary

What are the causes of fever?

Fever is usually related to the stimulation of the body's immune system, as it helps fight off certain disease-causing organisms.

Among the most common causes are:

  • Infections.
  • Inflammatory or autoimmune disorders.
  • Blood clots and thrombophlebitis.
  • Medications (some antibiotics, antihistamines and anticonvulsants).
  • Amphetamine abuse and withdrawal from a psychotropic substance in an addict.
  • The reception of heat emitted by industrial machinery or by heat stroke.
  • The first symptom of cancer may be fever.

How is a fever treated?

The most commonly used drugs in the treatment of fever are paracetamol and non-steroidal anti-inflammatory drugs, such as ibuprofen and acetylsalicylic acid (not for use in children). Also corticosteroids can be effective, but have many other effects that do not make their use advisable in this indication.

On many occasions, physical measures to lower the temperature, such as wet compresses or warm baths, may be sufficient.

The definitive treatment of the fever will always be the treatment of the illness that causes it.

Where do we treat it?


The Department of Internal Medicine
of the Clínica Universidad de Navarra

Its integrative vision and polyvalence allow us to provide the best medical assistance to multipathological and multisymptomatic patients, who present a difficult diagnosis or who suffer from prevalent diseases of a hospital nature.

Imagen de la fachada de consultas de la sede en Pamplona de la Clínica Universidad de Navarra

Why at the Clínica?

  • State-of-the-art diagnostic technology.
  • Quick diagnosis to start the most appropriate treatment early.
  • Teamwork with the rest of the professionals in the Clinic.

Our team of professionals