Just for those who may have to have one done, I wanted to post my experience. The doctor wanted to do the pharmaceutical test due to the CFS. I said okay, but later I did some research on the side effects and because I am very sensitive to chemicals and have gallbladder (nausea) problems decided to try and do the treadmill test. So I called her office before test and she said that was fine, that I could try the treadmill. So, the staff at the Cardiovascular center was super nice, but girl doing the "resting" pictures could not get a picture because of the thickness of my breast tissue. So, she had to start an IV anyway, but she did it in my arm so it wouldn't hurt as bad. Then she put some stuff, forgot the name, that made bubbles in my blood so she could get good pictures of the walls of my heart. This was not medicine, so it did not bother me at all. It was just to make bubbles. I felt just a little "bubbly" light-headed feeling for a minute. Then I got on the treadmill to gradually raise my heartrate. My blood pressure was low as usual. I did fine, except for lightheadedness halfway through. Kept on going, then right went I almost got to the top of my heartrate (180) I felt like I was going to pass out and I said I'm gonna pass out and jumped on the side of the treadmill. She said, no, get back on, they freaked because we were almost there. So I got back on and they supported me while she put more bubbles in my iv. Then I walked for a minute, then jumped back on the table for the "after" pictures. Today, I have been in flare all day from that, it wore me out. Terrible migraine, etc. Been out of it all day. If I had to do it over again, not sure if I just wouldn't try the pharmaceutical test. Anyway, won't get results for a few days probably. Expect it to show normal, just like every other test we do. Also, dress comfortably, I wore capris and a shirt. Also, wear tennis shoes. They gave me a gown to put on over my capris. This is so they can put the electrodes and a belt around you. Hope this helps someone.