Non-medical users of anabolic steroids often “stack” different anabolic steroids over the course of a “cycle” of use. They also administer various ancillary drugs and substances to enhance the desired effects of anabolic steroids or to minimize adverse side effects. The most common liquid (injectable) anabolic steroids encountered in these cases are (oil-based) esters of testosterone (., testosterone cypionate, testosterone enanthate, and testosterone propionate, and a blend of testosterone esters called Sustanon 250) or nandrolone (., nandrolone decanoate). Also popular are Equipoise (boldenone undecylenate) and trenbolone acetate and trenbolone enanthate, as well as the water-based injectable Winstrol (stanozolol). Popular oral anabolic steroids include methandrostenolone (Dianbol), oxandrolone (Anavar) and oxymetholone (Anadrol 50).
Injectable steroids are injected into muscle tissue, not into the veins. They are slowly released from the muscles into the rest of the body, and may be detectable for months after last use. Injectable steroids can be oil-based or water-based. Injectable anabolic steroids which are oil-based have longer half-life than water-based steroids. Both steroid types have much longer half-lives than oral anabolic steroids. And this is proving to be a drawback for injectables as they have high probability of being detected in drug screening since their clearance times tend to be longer than orals. Athletes resolve this problem by using injectable testosterone early in the cycle then switch to orals when approaching the end of the cycle and drug testing is imminent.
Testosterone can be administered parenterally , but it has more irregular prolonged absorption time and greater activity in muscle in enanthate , undecanoate , or cypionate ester form. These derivatives are hydrolyzed to release free testosterone at the site of injection; absorption rate (and thus injection schedule) varies among different esters, but medical injections are normally done anywhere between semi-weekly to once every 12 weeks. A more frequent schedule may be desirable in order to maintain a more constant level of hormone in the system.  Injectable steroids are typically administered into the muscle, not into the vein, to avoid sudden changes in the amount of the drug in the bloodstream. In addition, because estered testosterone is dissolved in oil, intravenous injection has the potential to cause a dangerous embolism (clot) in the bloodstream.