Man in all my years I never hit blood. Anyway while pinning 100 mg / 1ml of test pro I hit blood and didn't know it. Yes I'm usually more careful. So when I pulled out I bled like a MF. So I'm OK and It will be sore and prob black n blue but I never thought about how effective the pin would be. Same thing I would suppose, just not a good idea and ugly in the end...huh ...crazy mike