I don't take anything. increasing blood volume (or "thickness") is one of the anabolic benefits and attributes that come from taking things like Deca, Anadrol, Tren. you have more muscle building potential with more blood. you also have more work capacity potential. and the reason why bodybuilders in contest prep will take drugs like EPO to dramatically increase their blood thickness , is that these will show up in the physique as fuller, rounder, harder, and more vascular muscle.
so taking something to 'thin the blood' , when the whole benefit of some of these compounds is to actually 'thicken the blood' , is counter productive .. the answer is to simply not take these type of steroids in the first place if you don't want thicker blood (but in bodybuilding and some sports, the thicker blood is a big benefit and reason to take the drugs).
note: of course having 'thick blood' chronically months on end year after year is not healthy . taking time off these drugs and donating blood takes care of the issue for the most part and prevent "Chronic" high rbc and hematocrit