It is important to start a PCT once you finished a steroid cycle to avoid a dramatic loss of the mass gained. The question on how soon to initiate a PCT depends on the kind of steroids you used. If your cycle is comprised of orals, which have relatively the shortest effect on the body, it is advised to start immediately. Some say PCT can begin as early as the last day of the steroid cycle. If short-acting esters or water-based injectables, PCT is recommended 4-7 days after the last injection. In the case of long-acting esters, it should be around 10-14 days after the last injection.