I can be kind of uncomfortable, and a bit embarrassing. I did mine at GWU hospital - the nurse and doctors were all very nice, but it does involve a lot of poking around in your personal space, and contorting yourself so they can get a good image.
You should know the results right away - basically they inject dye into your uterus and if it spills out the fallopian tubes, they're open. You can see that happen right on the screen. My tubes were open so there was just some cramping from the dye being put in (like menstrual cramps, but you're stretched out on an examining table and can't curl up like you would in your own bed). If your tubes are blocked, I've heard it hurts. (I'm not trying to scare you -- sorry if it did.)
I went back to work in the afternoon, but wish I'd just gone home. I found it more emotionally stressful than anything else.
I've had two with very different experiences. First one was in the hospital radiation dept. recommended by my Gyno. I took nothing to relax me (such as ibuprofen). It was done by a female radiologist and nurse. The table was really uncomfortable and I had the worst cramps ever afterwards. I really was holding my stomach like a pregnant lady in labor in the middle of the emergency room wanting to scream at my husband because he was texting on his blackberry while walking to the car which only slowed down the entire process of me getting home swiftly.
A couple months later after being referred to SHFS, I had another HSG done in Rockville and it was smooth sailing. This time I took 2 ibuprofen before, table was much more comforable and I felt a little cramping but only because the Dr was trying to push the dye through my tube.
Both ended in the same result - blocked tube & I've heard in some instances having a blocked tube makes it hurt worse. Not sure if there's any truth to it, but taking ibuprofen surely did alleviate the cramping.
i have to get one soon too, it's eye opening to read these responses!