Another good trick for the thin veins is to put a hotpack on the spot they want to use for blood. I had a phlebotomist once look at my elbows and say that neither was gonna work, even with a butterfly. She whipped out one of those instant hotpacks and put it in my elbow, said "Don't leave!" and came back a few minutes later.

The elbow was much more sensitive, but the heat made the vein big enough she could get it. I only had a little bruise from that one.

Also try drinking extra water for the hour before the draw to avoid any possible dehydration and running up and down the steps a few times to heat up before you walk in the lab. (more tricks phlebotomists have told me over the years)

I just wish they could draw from the big varicose vein in my leg... I keep offering, but they can't use it, darn! (risk of throwing a clot is too high)