Fever in Adults: Overview

Man with fever holding thermometer


The normal body temperature is about 98.6°F but may vary by 0.9°F to 1.8°F. In a healthy afebrile person, the hypothalamic thermoregulatory center of the brain regulates body temperature by balancing the heat produced during metabolism and that which is released during respiration and evaporation.

However, when this balance is offset due to different reasons, fever sets in.

What is fever?

  • Fever is considered a natural reaction when the body is ill and is one of the oldest indications of disease. It often occurs due to infection, inflammation, or trauma to the body. Because fever is a response of the body involving multi-systemic mechanisms that occur when the body is ill, it is considered a significant contributor to the pathogenesis, clinical presentation, and outcome of many illnesses and diseases.

  • Fever Duration
    Acute < 7 days and characteristic of most infectious diseases.
    Subacute Not more than 2 weeks and seen in certain infections such as typhoid fever.
    Chronic Also know as persistent fever lasting for > 2 weeks and typical in chronic bacterical infections such a tuberculosis, cancres, and viral infections like HIV. 

    Fevers can also have specific patterns depending on cause, and this, together with other signs and symptoms, is used to diagnose the underlying disease, infection, or condition.

Read more about fever in adults

Fever in Adults: causes icon

What causes fever in adults?

Learn more about the causes of fever in adults.

Find out more

Fever in Adults: symptoms icon

How do adults present?

Refresh your knowledge on the signs and symptoms of fever and learn about “red flag” symptoms that require medical attention.

Find out more

Advil pack shots

Advil’s proven efficacy and safety profile

Discover why experts and patients have trusted Advil for over 35 years.

Find out more

management icon

What can you recommend to relieve fever in adults?

Find out more about both nonpharmacologic and pharmacologic treatments.

Learn more


Watch Advil in action

Watch our new MOA video to learn more about the science behind Advil.

Watch now

Patient resources icon

Patient care resources

Access educational resources for your patients, to help them have a better understanding of their pain condition.

Learn more