They will often feel ill after eating and may get nausea and discomfort in the upper abdomen. Weight loss is common in patients with giardia. This will evaluate for inflammatory bowel diseases such as ulcerative colitis and Crohn disease. These diseases are often found when persons complain of bloody diarrhea. Removal of the lower part of the small intestine can result in malabsorption of bile salts which can cause diarrhea.
Tests are available to determine if milk sugar is being absorbed normally.
These are really quite rare. The diarrhea tends to be intermittent and may alternate with constipation. The patient is often a young female. She usually has lower abdominal pain which may be quite severe. The pain tends to go away after several loose bowel movements.