Between growing up in the military, being in the military, traveling all over the world, being in the fire service, and all the usual mishaps and accidents that happen along the way I've been stuck with more needles than I can count. I've been vaccinated against diseases that only exist in labs, had at least a dozen tetnis shots, been tested for TB so many times that I now test positive for it and have to have x-rays to prove I don't have it, had a flu shot every year for the last decade plus, and started an IV on myself in a combat zone. A hundred needle sticks in my lifetime is probably a conservative number, and that's just before I started using AAS.
Being the twisted kinda guy I am, I watch every injection intently cuz I actually enjoy them now. Never since the first immunization I had as a child has anyone ever switched to a different needle than they used to draw to do an injection. Flu injection a month ago, she drew and pinned with the same needle for everyone that she was pinning that day.
It might be more right to switch to a new needle to stick after drawing, but it's hardly anything that's going to cause any sort of trauma that I'm going to be unable to cope with. When I first started pinning myself I would switch every time. Out of curiosity, one day I tried pinning myself with the same needle and it went in just as smoothly and still didn't hurt. Been doing it ever since. It's not something I do just for the purpose of saving money. I couldn't care less about $40. But it is nice to not waste that money for no real reason.
And you are absolutely not supposed to pin someone with the same needle you draw from.
If you really want to split hairs, none of us are ever supposed to be injecting ourselves with supraphysiologic doses of testosterone or any other hormones at all for that matter. And especially not from UGL's where we can't be sure of the sterility or even what is in the vial. Is not switching to a new needle to inject really gonna where you draw the line?