I am an RN...and give more than 30 IM injections per week...for the last 8 years. I never aspirate. In school, we were told that it's an out of date practice. That if you inject in the proper sites, then your risk of hitting anything substantial is almost impossible, and if you've been giving injects for years, you should know how to site properly. I know, lots of people here have seen blood after aspirating and pulled out thinking they hit a vein or something. or they've seen blood literally squirt out of the site after removing the needle. What they don't know is that this is usually a sign that they have busted a small capillary will going in and it bleed briefly. the chances of hitting a vein or artery are almost nothing if you are going in the delts, glutes and quads. And the chances of actually hitting something and the needle remaining in the proper space to actually injcet into a vein is almost unthinkable. I would say you are at risk if you are going anyhere else (biceps). I recommend everybody who doesn't have professional experience to aspirate...but, in the my clinic...no RN's aspirate.