Sick woman taking her temperature

Low-Grade Fever - Causes


Healthgrades Editorial Staff

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:

  • Cancers, such as leukemia or lymphoma

  • Immunization reaction

  • Inflammatory bowel disease (includes Crohn’s disease, ulcerative colitis)

  • Medication side effects

  • Pulmonary embolism (blood clot that travels to the lung)

  • Rheumatoid arthritis (chronic autoimmune disease characterized by joint inflammation)

  • Teething

  • Vasculitis (inflammation of blood vessels)

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:

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  • 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:

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  • 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 immun