A clot
A man walks into a hospital and notices another man masturbating.
He asks the nurse why he is doing this.
The nurse informs him that if he does not masturbate every 6 hours, a clot will form and he will die.
Then he notices a nurse giving a blow job to a man in the adjacent room.
“You’ll have to explain this,” he says afterward.
“Same problem, better insurance,” the nurse replies.