while it's best to use a differnet needle I do it a lot out of convience......most, if not all, infections are from contaminated gear, not dirty skin.....I give IM injections every day in the dirtiest place on the body, the mouth, and my patients never get an infection....I also give them multiple injections with the same needle....again, it's best to use a new nedle but injecting with the same one shouldn't be a problem......