I'm on my third day of taking vsl 3 probiotic and have horrible diarrhea. is this a common side effect?

Probiotic troubles: I wonder whether the diarrhea might have come from some antibiotics that were given recently or this product? Sometimes there can be abdominal discomfort or even diarrhea with these products - depending on your tolerances. You should probably stop taking them and call your GI doctor for help. In the mean time, taking in some fluids/chicken soup will help with the volume losses. Hope u feel better.