Causes of fatigue can be behavioral, psychological or biological in nature. Therefore, the origin of fatigue can be difficult to medically diagnose.

Many liver diseases, including viral hepatitis, cirrhosis, hemochromatosis and fatty liver affect the liver’s ability to process nutrients and toxins. This may produce fatigue. Other interruptions in the digestive process, such as bleeding from peptic ulcers or the malabsorption of nutrients may also affect functioning and eventually produce fatigue.

Debilitating conditions such as inflammatory bowel disease and ulcerative colitis also produce fatigue. Fatigue can also result from anemia related to gastrointestinal stromal tumors. These rare and often cancerous growths can occur anywhere in the digestive tract, particularly the stomach.

In some cases, fatigue can result from medications used to treat diseases. For example, fatigue is a side effect of a drug commonly used to treat hepatitis C. Other drugs, such as beta blocker heart drugs and antihistamines (common cold medications), can also cause fatigue.

Behavioral causes of fatigue may include:

• Lack of sleep
• Inactivity
• Overexertion
• Poor eating habits
• Dehydration
• Excessive consumption of alcohol or caffeine
• Use of illegal drugs

Fatigue caused by these factors may subside naturally or with a few simple lifestyle changes, such as engaging in regular exercise or going to bed an hour earlier. Individuals may choose to keep a diary to help identify the time of day in which fatigue is most prevalent so they can adjust their schedule accordingly.

Psychological factors that can produce fatigue may include:

• Stress
• Anxiety
• Depression
• Grief