Sustanon is a blend of four different testosterone esters. Esters are attached to steroids for the main purpose of making it more lipophilic. This way, the steroid remains in the adipose tissue longer when injected and is released slowly in the bloodstream over time. Longer esters are more lipophilic while shorter esters are less lipophilic. Sustanon, in it's most common form - sustanon 250 - is a unique blend of one long ester, one short ester and two medium length esters. The purpose for this blend is to provide the user with a quick release of the steroid, but also a long lasting one.
Sustanon acts as a time released steroid which is high in both anabolic and androgenic value. The fastest acting ester of the blend - testosterone propionate - becomes active in the first day. The other esters become active over the several weeks to follow where they reach a peak with the actions of all four esters which remain for the remainder of the cycle.
The athlete using sustanon can expect rapid increases in strength and fat free mass. Sustanon does aromatize, but slightly less than some other single ester testosterones which leads to less water retention when compared to other steroids.