Testosterone base is an injectable preparation containing testosterone (no ester) in a Oil base.
Among bodybuilders, “base” is known to be an extremely potent mass agent. It is often ranked as the most powerful injectable steroid available, resulting in an incredibly rapid gain of muscle mass and strength. This is largely due to the very fast action of this drug, as the water-based steroid will begin to enter the blood stream almost immediately after an injection is given. Unlike longer esters such as enanthate or cypionate which take weeks for blood levels to reach maximiun theraputic levels, with base it is just a matter of days. Clearly the anabolic effect of this testosterone will be realized much more quickly than we would expect with an oil based (esterified) preparation.