He loads up the syringe and says Jason's breathing will slow down if he has Cushing's. "Give it to her first," Jason says. House can't believe it! Jason said he wouldn't test the drugs on Hadley anymore! "I lied," Jason says. He may trust House now, but he doesn't trust the SWAT team outside not to give him fake drugs. House keeps arguing, saying the drug could screw up Hadley's liver because of her Huntington's. Hadley grabs the syringe (the way she should have grabbed the gun before House gave it back to Jason) and shoots herself up, saying her chances with the drug are better than their chances not being shot if she doesn't take it.
Jason expresses interest in Hadley's condition, asking her how long she has to live while House shoots him up. House listens for a respiratory reaction from Jason, but there isn't one. Meanwhile, one effect of the steroid seems to be that it makes people philosophical. Jason says not knowing what was wrong with him was driving him crazy, so he resorted to some crazy means to get his answer. "But I had something to gain," he says, pointing out that Hadley takes risks with no upside at all. But Hadley does get an upside: attention. House tells Jason that he isn't really the best person to be giving out advice, then notices that Hadley isn't looking so well. She's got a fever and her heart is racing. Meanwhile, Jason's breathing is the same. So not only was the diagnosis incorrect, but now Jason's guinea pig's kidneys are shutting down, thanks to all the medicine Jason "made" her take. Except not really, since she wouldn't have taken the steroid if House hadn't given Jason back the gun and she wasn't so ready, willing, and able to take all of them in the first place.
After the break, Hadley's kidneys are hurting. House calls the Cottages to ask why the steroid made her kidneys fail and not Jason's. Cameron suggests that maybe one of the other medications Jason took during his sixteen-doctor-spree is protecting his kidneys. Someone might want to give some of that to Hadley if that's the case. House says he'll have to slap Jason for "diagnostic purposes." The slap produces a CGI twitch in Jason's cheek that House says must be due to a calcium deficiency from drugs that block calcium and are protecting his kidneys. Cameron says Jason has been on proton pump inhibitors for stomach pain for years. House says that means his kidneys have been protected for years. This allows him to add kidney failure to Jason's list of symptoms, since his kidneys would have failed a long time ago were it not for the PPIs.