What causes low-grade fever?

Fevers often accompany infections. Body temperature can be elevated by physical activity and environmental factors, such as wearing heavy clothing or a high ambient temperature. A low-grade fever may also occur following immunizations, during teething, or as a symptom of cancer or inflammatory and autoimmune conditions. It can also occur as side effect of some medications.

Infectious causes of low-grade fever

Low-grade fever may be caused by infections including:

  • Bacterial infection, such as Strep throat or scarlet fever
  • Cellulitis (skin infection)
  • Childhood diseases, such as chickenpox, fifth disease, measles (contagious viral infection also known as rubeola), mumps (viral infection that, in part, affects the salivary glands in the neck), whooping cough (pertussis)
  • Cold, flu, or other viral infections
  • Ear infection
  • Gastroenteritis (infection of the digestive tract)
  • HIV or AIDS
  • Lung infections, such as bronchitis, pneumonia, and tuberculosis
  • Mononucleosis (viral infection)
  • Parasitic infection
  • Sinus infection
  • Urinary tract infections

Other causes of low-grade fever

Low-grade fever can also be caused by conditions including:

Serious or life-threatening causes of low-grade fever

In some cases, low-grade fever may be a symptom of a serious or life-threatening condition that should be immediately evaluated in an emergency setting. These include:

  • Acute hepatitis (active infection of the liver)
  • Appendicitis
  • Cancers
  • Diverticulitis (inflammation of an abnormal pocket in the colon)
  • Encephalitis (inflammation of the brain)
  • Epiglottitis (life-threatening inflammation and swelling of the epiglottis, a tissue flap between the tongue and windpipe)
  • Heat exhaustion
  • Meningitis (infection or inflammation of the sac around the brain and spinal cord)
  • Osteomyelitis (bone infection)
  • Pancreatitis (inflammation of the pancreas)

Questions for diagnosing the cause of low-grade fever

To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your low-grade fever including:

  • How long have you had a low-grade fever?
  • Does it come and go, or is it constant?
  • Does anything make it go away?
  • Do you have any chronic medical problems or a weakened immune system?
  • Have you traveled recently?
  • Do you have any other symptoms?
  • What medications are you taking?

What are the potential complications of low-grade fever?

Because low-grade fever can be due to serious diseases, failure to seek treatment if it is persistent or accompanied by concerning symptoms, or if you have chronic medical conditions or a weakened immune system, can result in serious complications and permanent damage. Once the underlying cause is diagnosed, it is important for you to follow the treatment plan that you and your health care professional design specifically for you to reduce the risk of potential complications including:

  • Anemia (low red blood cell count)
  • Brain damage
  • Cirrhosis (scarring of the liver)
  • Heat stroke
  • Peritonitis (infection of the lining that surrounds the abdomen)
  • Physical disability
  • Sepsis (life-threatening bacterial blood infection)
  • Shock
  • Spread of cancer
  • Spread of infection


  1. Fever. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/003090.htm.
  2. Fever. FamilyDoctor.org. http://familydoctor.org/online/famdocen/home/tools/symptom/503.html.

What is low-grade fever?

A fever is an increase in the body temperature above normal. A low-grade fever is a mild elevation of the temperature above normal. Your temperature measurements fluctuate through the day and vary depending upon the site of measurement. Generally, a child is considered to have a fever if the temperature is at or above 100.4 degrees Fahrenheit rectally, 99.5 degrees Fahrenheit orally, or 99... Read more about low-grade feverintroduction


What other symptoms might occur with low-grade fever?

Low-grade fever may accompany other symptoms that vary depending on the underlying disease, disorder or condition. Conditions that frequently affect your temperature may also involve other systems.

Infection symptoms that may occur along with low-grade fever

Low-grade fever may accompany other symptoms of infection including:

Medical Reviewer: Cynthia Haines, MD Last Annual Review Date: Aug 5, 2013 Copyright: © Copyright 2014 Health Grades, Inc. All rights reserved. May not be reproduced or reprinted without permission from Health Grades, Inc. Use of this information is governed by the HealthGrades User Agreement.

This Article is Filed Under: Infections and Contagious Diseases

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