I am in the medical field and would just like to throw out there my 2 cents. I'm sure most of you already know that anytime you draw anything up to clean the top of the vial before drawing up. Use a fresh sterile needle if your going to be going back inside that vial (to avoid contaminating the sterility inside of the vial),and always use a fresh sterile needle before injecting. Of course clean the site thoroughly before pinning, and if you touch the site with or without gloves its considered contaminated and needs to be cleaned again. You have bacteria on your skin and when you push a needle through, your also pushing through bacteria. So using clean technique is very important. When I was in school they showed us microscopic pictures of reused needles. After the first prick it is already dull. After the third or fourth the sucker looks like a fish hook. Now imagine trying to push a fish hook in then pull it straight out! I get cauliflower ear now and then and in order to keep training I have to drain it with a syringe. Drs cost too much! Ive used both insulin syringes and IM to drain my ear and a few times ive reused (I know I know but I was out and I had to train!!!) I know I'd rather use a fresh one any day. Re-using hurts like a bitch and its high risk for infection! When I'm finished I recap (only my own needle, not in the field) and put it in a sharps container. Sharps containers, when taken to the right places will be burned in an inferno as Bio-Hazard material to be fully disposed of. Hope that helps.