There’s no blood test for helium addiction as helium unlike oxygen cannot be absorbed into the blood stream, it simply fills the lungs and prevents some oxygen from being absorbed which does give a general sense of lite headedness. Some users do not inhale, which is worse. They suck a big mouth full until their cheeks puff out and then squeeze the helium out their ear canal while holding their nose with their fingers. this does force some helium into the brain where it cannot escape if the user’s skull has completely hardened leaving no soft spot. some teens sometimes temporarily regrow this soft spot as they grow and when this happens the helium can escape. others have learned that the ancient surgical practice of trepanning can also release helium (not to mention evil demons but we’ll save that conversation for a post on Mariah Carey)