Irritable bowel syndrome (IBS) can cause a variety of symptoms. They commonly occur after eating or when under stress. Symptoms may vary among patients and can range from mild to severe in intensity. Symptoms of IBS include:

• Abdominal pain. Abdominal pain or cramping associated with bowel functioning is the most common symptom of IBS. Stress and eating may worsen the pain, which usually occurs in the lower left-hand side of the abdomen. Patients with IBS may experience episodes of dull aches or cramps that can range from mild to severe. The pain is often alleviated with a bowel movement. For women, pain may occur or intensify during their menstrual cycle.
  
  
• Diarrhea. Loose, watery stool. Bowel movements most often occur after eating or upon awakening. Diarrhea is usually preceded by a sense of urgency and may be followed by a sensation of incomplete defecation. Soiling may occur as a result of diarrhea.
  
  
• Constipation. Difficulty or straining during a bowel movement, usually involving hard, pellet-shaped stool. Constipation may last days to months in patients with IBS. It is occasionally accompanied by a feeling of incomplete defecation, even when the rectum is empty. Chronic constipation in patients with IBS may lead to straining and the misuse of laxatives or enemas. Patients with IBS may have an urge to defecate, but are unable to do so. Mucus may appear in the stool.
  
  
• Bloating. Gas buildup in the intestines, which can create a sense of increasing pressure in the abdomen. Patients with IBS may experience a swollen or distended abdomen as a result of bloating, as well as an early feeling of fullness when eating. Gas can stretch the bowel and cause cramping or abdominal pain in patients with IBS. Belching may also occur.
  
  
• Other digestive problems. Other gastrointestinal symptoms that can be experienced by patients with IBS include indigestion (including heartburn and nausea) and difficulty swallowing. However, these symptoms may be a symptom of another gastrointestinal problem and not attributed to IBS unless other problems are excluded.
  
  
• Problems outside the digestive tract. Symptoms outside the digestive tract may also appear in patients with IBS. These include fatigue, headaches, back pain, fibromyalgia (a syndrome causing chronic pain), frequent urination, painful menstruation and sexual problems (e.g., painful intercourse or lowered sexual drive).

Symptoms almost always occur while a person is awake. It is rare for symptoms such as diarrhea or abdominal pain to wake patients with IBS from sleep.

Symptoms of IBS are sometimes confused with celiac disease, malabsorption problems and inflammatory bowel diseases (e.g., Crohn's disease and ulcerative colitis). The following are not symptoms of IBS and may indicate other medical problems:

• Bleeding
• Fever
• Unexplained weight loss
• Persistent, severe pain
• Nocturnal diarrhea (diarrhea that awakens a person)