Everyone seems to respond a little differently. There is no exact science to it. I have a couple guys that take 500iu HCG every 3 days and any less doesn't seem to keep their testes at full size. I know another guy that is good with 250iu 2x wk. But no one I work with is currently using more than 500iu 2x wk. Just based on my expereince with others, I think you'll be fine with 500iu every 4 days.