"Not Drunk" joke

A man is driving down the road somewhat erratically. A cop notices this and pulls him over. He walks up to the window and says:

"Sir, I believe you`re drunk. I`m going to administer a breathalyzer test"

Man, sheepishly: "Oh, I`m sorry officer, I`m a severe asthmatic, and I don`t have my inhaler with me... if I blow into that thing I could have an attack and die"

Cop, a little distrustful: "Uh, yeah... well, this is more invasive, but if you won`t submit to a breathalyzer, I`m going to have to take you down to the station and take some blood sample"

Man: "Yeah, well, see, the thing is, I`m a terrible hemophiliac, and so I can`t give blood... I might die"

Cop, clearly frustrated: "Alright buddy, well, this is imprecise, but I`m going to have to have you get out of your vehicle and walk this line heel-toe"

Man: "Oh, I`m sorry officer, I can`t do that, I`m drunk."