Testosterone propionate is an oil-based injectable testosterone. The added propionate extends the activity of the testosterone but it is still much faster acting than other testosterone esters such as Cypionate and Enanthate. While cypionate and enanthate are injected weekly, propionate is most commonly injected at least every third day to keep blood levels relatively steady. For strength and muscle mass gains, this drug is quite effective. With propionate, androgenic side effects seem somewhat less pronounced than with the other testosterones.