Whenever you want to boost your ball size a little. Some do it twice a week, some once a week, some ED, some every 5, whatever, you get my point.. It does not matter what day you take it on. If you are on a long ester, which I am guessing you are, the test should be in full swing in your system by week 4. Doing an hCG shot the day before, day of, or day after will not matter one bit.