You can take it subQ or IM. I take on Mon/Thurs, sub Q. It doesn't matter much when you take your hcg shot in relationship to when you take the test shot for the following reasons:
1. If you are taking a long ester test, like cyp, its active life is about 14 days and since it is long, it is also slow, meaning that the shot you took two days ago is not really an issue. Your levels are from the shots you took 1-2 weeks ago.
2. If your are taking a fast acting test or mix like sustanon, where you are pinning every day or two, it doesnt matter when you take the hcg, because you are always pinning anyway.
The only thing my DR. told me about timing was not to take the hcg within 15 minutes of eating. (dont know the reason for that)
I have heard about mixing the test and hcg in same pin, but have never done it. Heard that it works just fine though. I pin subQ to belly fat because of fat burning properties associated with hcg.
Good luck