When I lived in Provo, Utah I sold my blood plasma for money. The plasma center, Pyramid Biological, was a horrible place. It was full of young nurses in training who had the job of inserting the 16-gauge needle into the arms of plasma donors, or »sticking«.
One time, I was stuck by an inexperienced nurse. She had stuck the needle through one side of the vein in my arm and out the other side. So while the needle was able to draw some blood from the vein, when the cycle reversed and the plasma-free blood was pumped back into my arm the blood went straight into my muscle tissue. It hurt like fuck.