On advice of my doctor, Started taking 5 mg Melatonin tablets at night to help with sleep disturbances I was having. Melatonin worked great for the sleep problems and still does. However, after 3-4 weeks, I started getting watery stools, then explosive diarrhea at times. # of BM's was 3-4 a day, after eating (normal for me) but my bowel movements were almost disabling. At times, I would get stomach cramps and had to race to the toilet as fast as I could. Other times, I would feel BM coming, feel some gurgling in my intestine and when I got to the bowl it was like someone turned on a fire hydrant. Then I would be fine. Felt a little tired and needed more sleep at night, but that was OK. No nausea. I was away at the beach on vacation anyway. Initially, lost about 10 pounds(which I wanted to do anyway, so I was not alarmed by that). After a few weeks, weight plateaued. I had a healthy appetite, which was frustrating while I ate bland foods and drank seltzer water only(no milk) to eliminate allergies and bad water as potential causes. After 3 weeks, I gave up on the food precautions and ate anything near me and gained back 2-3 pounds but the diarrhea remained exactly the same. Outside of the bathroom, I felt pretty good. Like clockwork, the watery stools and/or diarrhea continued. It was not at all like the Giardia that I had 2 years ago that was totally debilitating. Returned home and went to doctor who wanted to test my stools, but insisted that the lab would only do the 3 tests she needed if I submitted liquid only stools. Many plastic containers and rubber gloves later, I discovered that I was not able to retrieve a liquid only sample. I checked online yesterday and discovered HealingWell posts that matched my experiences EXACTLY. I stopped the Melatonin completely yesterday and put the stool tests on hold. The diarrhea is still the same (36 hours after my last Melatonin) but I will post a followup when diarrhea stops or in a few weeks if it does not.