That happened to me too! Old nurse they call 'Butcher Betty' Collapsed 3 veins trying to get blood from me. Apparently it's more common if the blood is taken early in the day and you haven't had anything to drink.
https://i1065.photobucket.com/albums/u389/lj2245/bd398de7.jpg
https://i1065.photobucket.com/albums/u389/lj2245/bd398de7.jpg