I have been using testim for some time now, probably 18 months. I upped the dose a few months back because my levels were still low ( I have no ovaries so need more than usual) and when I upped the dose I could feel the difference I would say within 3 to 4 weeks. So one tube now lasts me a week. I experimented in the summer with dropping back down a bit but definitely then didn't feel so good so am now back to tube a week. It does seem to be the missing link for a lot of women.