There are a few different types of stress tests.
One is an exercise one where you are monitored while walking a treadmill. The treadmill inclines more and more and gets harder to keep up with. No medications are used. Usually done as a baseline indicator. Often they will use the exercise stress test with an echo cardiogram, taking ultrasound pics before and after the test.
There is a Nuclear stress test. In this one you get a bit of Thallium injected by IV. Then they give you a nuclear heart scan to see what you heart is looking like and how it is pumping. Then you walk on the treadmill, same as the exercise test. After the treadmill part you get taken back to the nuclear scan and they scan you again, looking for changes etc. This one is a fasting test, where you can't eat or drink anything for about 12 hours. One doc told me 12 hours (first 3 tests I had) and the next doc I had made it 24 hours (the last test I have had). The 24 one did not go very well and I think it was way too long without at least water. Hard to exercise when dying of thirst. LOL!
If for some reason you can't do the treadmill part of the Nuclear stress test, they can give you a medically induced stress test using dobutimine (sp) or persantine to artificially stress your heart. You still get some kind of nuclear meds also and still have the nuclear scans before and after. I had to do the "nothing after midnight" for this test. It's a mite weird when you are lying there and all of a sudden the heart starts going rinky-dink. But it's over soon.
All tests had the no caffeine for 24 hours rule but the "nothing by mouth" seems to vary.
HTH a little bit. I've had all of the above, with the last one having to be artificially/medically induced.
Take care and let us know how it goes!
Suzi