Fructose intolerance is often misdiagnosed as irritable bowel syndrome (IBS). Both conditions can cause similar symptoms of vomiting, diarrhea, bloating, and abdominal pain. Neither illness causes the other, but some people can have both conditions simultaneously. Some people have found that fructose can exacerbate discomfort from IBS. A liver biopsy, fructose tolerance test, or DNA test can diagnose fructose intolerance.