If your gains aren't any better on than off, you'll know you have a problem. Also, if you don't get ANY sides like itchy nips, sleeplessness at night, night sweats, acne, wicked pumps, test dick if UR doing test, deca dick if UR doing higher levels of deca, nipple hard-ons when you train, shrunken nuts...you know, the usual stuff associated with higher test levels.