I wasn't able to find a reference, but I believe it's possible to go to a blood drive and have blood drawn and discarded. This provides cover for people who ar

I wasn't able to find a reference, but I believe it's possible to go to a blood drive and have blood drawn and discarded. This provides cover for people who are ineligible but don't want their friends/coworkers to know. Alternatively, it's easy to DIY if you are so inclined. You just need some sterile needles and alcohol swabs.