Finding the vein

I have good veins, or so the drawers of blood assure me. Good meaning easy to find and stick a needle into. Little blue highways running right below the skin in the crooks of my elbows. Might as well have flashing arrows.

Other people are not so lucky. They suffer multiple exploratory punctures when in a situation that calls for blood to be drawn. Bad enough to have a needle in your arm. Worse