This is the last I am going to write about this subject, I promise, unless I come across anything so radical it changes everything. I have spent all day researching everything I could about T., it has been me, internet, library and a shaving cut that has been killing me all day. While I appreciate all comments and appreciate the motivation to do my homework, I have found nothing that goes against doing T. every 3 weeks. As many of the comments said the "recommended" dosing is every 4 weeks, but as another comment said depending on how the body uses it, every 3 weeks is not a risk of PML. Of the 3 people who did get PML (2 with MS, 1 with Chrons) all of them were using T. in conjunction with another immunosuppressent, not just T. alone. There is no data of any kind of overdose, they are not sure what exactly that would entail, probably because of its short time on market and how strictly they are watching it. Which brings me to my next point, the infusion center keeps tabs on everyone who receives T. and keeps records of every time you have an infusion and submits those records to the TOUCH program. Therefore I want to say again that I am sure I am not the only one who does it on a 3 week schedule. There is an estimate of over 10,000 people on T. now in the U.S. alone and I can't remember what the U.S. and Europe number was, I believe over 12,000, so I doubt I am alone, and so far no new cases of PML, but many cases of improved quality of life, YEE HAW! But don't take my word for it, ask, read, just don't cut yourself shaving.