After being diabetic for over 20 years and verious other reasons for having blood taken, I dread to think how many pints so far have been tested...
If you taken something like a apsrine yes this can make the changes of brusing slightly higher etc... And if pressure isn't put on the cotton wool to stem and aid sealing then yes you bruise more..
But technique of the phlebotomist, nurse or doctor which really determines if and how much you might bruise..
The only time I've it painful is when the nurse or should I say the health care assistant that doing it, missed the vein and stuck the needle into my tendon (you have a tendon that runs through your elbow behind the main vien) and take my word it hurt not only when she did it but for a week or so afterwars...
Strange thing is though when I first started having bloods taken I used to hate it, scared the hell out of me.. But it was the old fashioned method of drawing off a syringe of blood, then squarting it into sample vials for the lab, (left overs squarted down the sink) so it was a relieve that the new system came in, where the clip sample bottle onto the end of the syringe.. What ever it's called..
But a couple of years ago at the main hospital, the phlebotomist tried my right arm, but my vien had gone into hidden, but instead of trying my left arm, she decided to wack me with the old fashioned syringe method, boy did feel fainted after that..