A question for my fellow vampires:

I have a blood draw coming up in the next week. Normally, I have veins you could hit with a harpoon from a door three blocks down. This, however, will be a fasting blood draw, and my veins disappear when I fast, no matter how much water I drink.

Would it be a breach of manners to show the phlebotomy guy my left radial vein and say, "This one, right here, with an eighteen-gauge butterfly"? It's at my wrist, which is an odd place, but then, I have odd anatomy (thanks, Mom!). Or is that considered sub-fusc?

Comments welcome. Last time, he had to stick me six times before getting enough blood for two vials.