Blood tests

Hey gals! So today I had to go to the hospital to get some blood drawn for some tests. They ended up taking 12 vials of blood; which is more then I've ever had at one time. My vein started to just drop blood about half way through. The needle was in my arm for about 13 minutes total. I've noticed that I've been extremely tired today and just feeling kinda off, could that be from that much blood being taken? Also, about how much blood was it all together? Thanks!