For my HIDA scan, I was injected with a radioactive dye. I layed down on a bed, not allowed to move, and had a camera hovering above my stomach for about an hour and a half as it took pics of the dye going into the gall bladder. Actually, I ended up drinking some water to push the dye through a bit faster because it took a lot longer than expected. Anyway, I then had to drink a surprisingly tasty chocolate shake that had 100 grams of fat, and I had to down it quickly. I then layed back down on the bed and the camera was again placed, hovering above my stomach for about an hour. I was planning on going back to work that afternoon, but there was no way that was gonna happen! I was out for the count for the next couple of days from drinking 100 grams of fat! Results showed my gall bladder was non-functioning...which explains why I was out for the count for a couple of days! My body just couldn't take the fat!!
It's a fairly simple test, but it does take a few hours. Good luck with the test!