well not necessarily, sure diabetics have on average a shorter lifespan but thats for various reasons b/c far more people let it go uncontrolled than they should, but I wouldnt suspect insulin itself would shorten your lifespan. however using it improperly can have negative effects on the body such as reducing the body's ability/want to produce its own and thus causing an increase to develop a form of diabetes. pretty much...dont be stupid with insulin