Does it really take that long for esters to 'kick in?' When I first went on HRT, the doctor gave me my first shot. The next day, I felt extremely different than the day before. The only way I can describe the feeling was that it was like I replaced a run-down battery with a fresh new one. Doesn't that mean that it is getting into your system already, or do you mean it takes that long for the test level to increase to its peak point? I had a blood test done in which my doctor compared my levels off the test and when I have just had a shot in the morning. Off, I measured 194. I took my shot the next morning and had my next test in about 2 hrs. The results of that one was 1314. So doesn't it release quickly into your bloodstream even with an ester?