Unfortunately after I go through the usual rigmarole of ticking off the questionaire, getting my iron level tested (trust me, it's the worst part of the whole process!), and getting my BP done, they ask me "Um, are you sure you have veins in this arm, cause we can't see any!" And then they move me to another chair so they can check my other arm. "Ooops, none there either!"
Luckily they contented themselves with a visual inspection and didn't have to go digging for them, but it was a bit embarassing. Especially when they insisted that I have a cup of tea and a biscuit anyway.
Oh well, at least they didn't try to make me lie down because "you look so pale dear, are you all right?"