Good morning and welcome!
Years and decades ago, I was on an HCG program in which I visited the clinic 3x a week. At that time, they did use one hip, then the other, just as you said.
The program I'm on now says to inject myself daily anywhere across the lower abdomen, like beside or beneath the bellybutton. And I am to alternate spots, staying about 2" away from the previous injection.
I do believe there are some who inject arms or thighs, or maybe other areas. I don't know if you get different results by the location of the injection.
Also, my syringe was supposed to be filled to .25,...cc's? I forget exactly, but it was definitely "25". You begin by drawing air into the syringe (to the "25", in my case), then inserting the needle into the vial and emptying all the air into the vial. This is so when you draw the liquid into the syringe, no vacuum develops in the vial.
Have you started the program? Started injections yet? Let us know how you're doing!
Karen