I know quite a few Marines / Army friends and family who come back with blood types sharpied on their boots and other semi-random places. Obviously they’re expected to know blood type and make it known. My question is for civilian life. Any EMT paramedics ER nurse/doctors etc who can answer this? I’m curious if it’s any help at all to have a blood type tag anywhere on your EDC. I can mark medical info on my phone available as emergency info or wear a WWJD OPOS bracelet, but does any of that ever get used? Do you guys search the person for this before giving blood or testing? If you see a tag reading ONEG or whatever do you trust it?