Hmmm... this discussion is frightening me! No one ever mentioned to me that constipation may be an issue with phentermine. Is this pretty common? I'm only on day one, so I'll have to see. Maybe it will actually help me out because I have IBS and it causes me to....now don't freak out...it causes me to go 4-6 times a day! If this can help me go less frequently then it may be a good side effect for me.