Self-transfusion can be detectable now that they have the athlete biological passport. At least, that's the intent of it. If your red blood cell count goes up f

Self-transfusion can be detectable now that they have the athlete biological passport. At least, that's the intent of it. If your red blood cell count goes up faster than is naturally possible, they'll be able to tell. This can't keep you from doing it very gradually, of course. Plus, basically all of these guys sleep in altitude tents now to boost red blood cell production via low oxygen. I don't think anyone has been caught doing it yet, but it's also possible now to use a carbon monoxide inhaler to induce hypoxia and boost red blood cell production that way. Escape Collective did an investigation into a few months ago. That is pretty dangerous, but it's hard to believe not a single person would at least try, and it can't be detected. It's not even actually banned right now, though UCI did ban huffing xenon gas to do the same thing. Detecting carbon monoxide huffing seems undetectable even in principle, though, since it's a naturally occurring pollutant. You'd effectively be banning riders from ever smoking since that would produce a positive test.