I've been thinking of doing it for a while but I'm worried that my diet of only coca cola and egg mcmuffins may make my blood poisonous to the average person
on a real note I have actually been thinking of doing it. did a mobile clinic go to you or did you go to a center? and was it a pleasant experience?
I'm an Australian living in Japan so I was interrogated for like 30 minutes to make sure I was an eligible donor. It was a mobile clinic that was set up in a hall in the bottom floor of my office building.
I've donated blood back home as well and its something Im really passionate about. There really is no other good source of usable human blood beyond willing volunteers. Any sort of financial compensation for blood donations is both ethically wrong and extremely dangerous. Everyone at blood donation clinics and drives are very sweet and enthusiastic. Blood donation clinics are always very heart-warming, feel good places because everyone there knows they're contributing to the good health of their society in a way only they can.
I can't promise exactly what it's like for your country but I know a lot of places have an option to register yourself as a blood donor so that you don't need to repeatedly fill out the same questionnaire. After that it's 10 minutes of very mild discomfort and then you get a bunch of cookies and juiceboxes and cute little blood related toys and merch.
There is a tendency all across the world for the nation's blood supply to constantly be below demand unless some sort of disaster is happening in which case everyone all of a sudden donates. Your local medical facilities need your blood the most during mundane, ordinary times. If you've been considering it, just walk into a clinic and ask. A lot of places are prepared to educate and accept walk-ins and you will likely be able to donate blood within the hour if you're deemed eligible.
Worst case scenario you feel a bit sick and ask to stop (you can back out at any time no questions asked, you can even back out after the donation within a small window if you no longer consent for you blood to be used in quite a lot of places.)
Best case scenario your blood directly saves somebody's life, and you get to eat the mounds of random cookies and shit they keep in any blood donation site.