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.
As for bodybuilders, stanozolol has one interesting peculiarity demanded among them. It consists in the profound ability to lower sex hormone-binding globulin (SHBG) level resulting in efficiency growing of other steroids in stack with it. In particular, it raises the amount of biologically active free testosterone circulating in the blood. For this reason it is advisable always to use stanozolol in stack with testosterone. Another one reason for this is as follows: winstrol may be more prone than other anabolic steroids to increasing tendon brittleness. This happens due to winstrol`s possibility to dry out the joint fluid, which can lead to joint pain and damages. Also both stanozolol forms: tablets and injections have been noted to provoke adverse changes in cholesterol levels. Hence, monitoring of the lipid profile of the body (blood works) during cycle is advisable.