dondada109 said:
If the same needle is used to draw from all 3 vials, you risk contaminating every one of them. That’s something I’d treat very carefully, because contamination can cause serious infections, sepsis included, and that’s a situation nobody wants to face.
For my part, I’d draw and inject with a fresh sterile needle every time, one per vial and one for the shot, even when that means spending a bit extra. Putting health and safety first matters most, particularly with research compounds or products from suppliers whose sterility and quality testing might not be fully confirmed (even more so when the exact vials and kits you have were not tested individually)