It's more than 12 years since I gave blood. Rheumatoid arthritis means they don't want my blood any more. Autoimmune disease.
When I was at college, there was a very poor juxtaposition of visiting vehicles one day: the blood service, asking for students' blood, and the Scottish & Newcastle Brewery's mobile bar, giving away free beer. I gave a pint of blood and then had 5 pints of something. Not to be recommended.