I get my pups blood drawn on Friday. Boxed it up real good with a big cold pack and a Styrofoam container for the blood vial from the vet. Go to the post office and advise them that the blood needed to reach its destination no later that Tuesday (today). Was advised that priority shipping would do the trick (weekend included) and that it would arrive at the U of M Monday. Checked the tracking info with the USPS Rep from the 800 # and was advised that the service that I paid for might not get to its destination until THURSDAY and anything after that would be considered late. I'll fight that battle later. Has anyone had there blood take longer to get to the U of M than it should have? What happened? How long does the blood last before it is no longer usable for testing. I iced it down pretty good. I'm crossing my fingers and hoping for the best.