passing through/nicking veins should happen... last week i pulled out and it just started running out. of course, i aspirated, and injected into muscle and not a vein. but when you pass through you should expect blood. todays shot on the other hand was smooth and just the usual tiny drop afterwards...though, some blood at the tip of the syringe...which is usually from passing through or nicking as well.. blood is ok.....as long as you aspirated and didnt shoot in a vein...