@tiss, I know it is late. I hope this reaches you before your test tomorrow. 10 years ago, I had arterial blood gas test as part of my evaluation for organ transplant. I don't remember it being as uncomfortable as I had feared or read about. The site was numbed before the procedure. It does not take long at all for the blood draw. I had it done on two different occasions, and each at a different facility. As with any blood draw, a whole lot depends upon the skill of the phlebotomist.