peak blood levels for enathate are achieved the day after an injection, with test levels gradually dereasing from there. However, 3-4 days after the initial inject, there is another. In this second injection, there is another spike on day two with the highest levels. But, some test is still left over from the first inject. So, while from day 2 of a shot, test levels have a localized downward trend until the next shot, the global trend of one's test levels in generally increasing because of the cumulative remaining esterfied test from prior injects.
However, there is a point in which the ester decay equals the quantity injected. This point is called "peak blood concentrations," and usually happens around week 3-4, that is why most people "feel" it around then (There are a few other reasons too, but I am not going to get into them). This is why I am a proponent of frontloading -peak blood levels as soon as the second day, and keeping them there the rest of the cycle. There is no reason for sub-optimum blood concentrations for 3-4 weeks at the beginning of a cycle, especially considering these sub-optimum levels are already shutting you down, whithout seeing optimal gains.