Long ago they used to take 1/2 pints - my very petite mom used to donate, but now with the amount of testing that they have to do on each donation it isn't worth the effort to take less than a full pint, so us small folks are no longer eligible.

My husband used to be a pretty regular donor (he's got a couple of those pins for # of gallons).... but they got him into platelets and plain wore him out, they were calling what felt like constantly (you can give much more often than whole blood), plus giving platelets is a longer and more involved process. He'll probably give again sometime, but at this point he's burned out...