In most cases, anorexia is not a serious symptom. Anorexia is most commonly associated with another primary illness, such as gastroenteritis or influenza. Many common viral infections also cause anorexia. Primary causes for anorexia include anorexia nervosa.

Anorexia may be due to another illness such as:

• Alcohol abuse
• Brain tumor
• Cancer
• Dehydration
• Diabetes
• Drug abuse
• Gastroenteritis
• Hepatitis
• HIV infection
• Influenza
• Intestinal obstruction
• Mononucleosis
• Pneumonia
• Thyroid disease
• Tonsillitis