FWIW, I *think* you're probably right that it's based on other physiological factors, but i find the same thing. They do a finger-prick iron level before I give blood, and i give regularly. When I'm on mast or tren, my pre-screening iron level does seem to be higher then on a Test or even Test & an oral. But it could just as easily be because of what I ate the day before. I try to stay away from red meats a couple days before I give so I don't get bounced out based on my iron levels.