I've had the problem where they're in the vein and nothing comes out. At once point I was getting blood tests every few days and my veins would just not give anything up so I had to drink loads of water, pump my fists, use hot packs and everything.
I get blood tests once a month now and I'm used to it so it's not bad. I can't look at the needle in my arm though even on TV hospital shows I can't watch anything get pushed into someone's skin!!