Hello, OP here! Thank You all for your concern! I'm doing a lot better. I actually ended up passing out three more times before they carted me off to the hospital, where I took a nice nap. I think what did me in was my blood pressure, which to me actually seemed low to give blood. I have normally low blood pressure (96/84 is my average) and it was 100/85, or something like that. They also did not attempt to detain me. As for the amount, they took 2 cups from me, so one of the smaller bags. This is a company that regularly visits my university (not the Red Cross, if it was Red Cross it would be different), and my sorority sister who took care of me had two bags taken from her last year, she's about 5'5" and weighs maybe 170lbs and she nearly passed out. I think the next time I give blood, it will be with RC. They made no attempt to stop me as I went up a flight of stairs, handed my meal card over, and made my way over to the pop machine, which is where I fainted for the first time in my life. Thank You again for your concern, and I'm so glad that I did it.