Okay - I know this is an old thread but I wanted to give an update.
To recap - my HCG came in 2 vials - one with the lyophilized HCG powder and one with the diluent. The diluent was a sodium phosphate solution. Injections were painful - I moved to my delts where I could tolerate the pain and continued using it over the following weeks.
Yesterday I finished that vial and had to resuspend the second lyophilized powder.
On the advice of Cortes, I got myself some sterile saline solution (0.9%) which was not meant for injecting and filtered it through a 0.2um filter and into the vial containing the HCG powder. I did not use the diluent that came with the HCG this time.
Injected last night and NO PAIN WHATSOEVER. It was a beautiful thing.
So if anybody out there gets HCG that comes with a sodium phosphate solution, I would hesitate to use it because it caused me a lot of unnecessary pain.