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.
Testosterone aromatizes very easily and therefore estrogen buildup and side effects can become an issue for users sensitive to these problems or those choosing to use a high dose of this compound. Therefore, when using Testosterone, bodybuilders often choose in incorporate an anti-estrogen such as Anastrozole, Proviron, Tamoxifen to help keep estrogen related side effects to a minimum. Extremely sensitive users, or users using very high doses (800-1200mgs) might find that stronger anti-estrogens such as Letrozole or Exemestane are more suitable. Androgenic side effects such as oily skin are also possible while taking Testosterone.
The side effects of Proviron will include the suppression of natural testosterone production, but it’s not as cut and dry compared to many steroids . The use of anabolic steroids, any anabolic steroid will suppress natural production; however, the rate of suppression varies greatly from one steroid to the next. In the case of Mesterolone, the total rate of suppression can be so minimal it can be insignificant. With standard Proviron doses, which normally fall in the 50-150mg per day range, the total suppression of natural testosterone production should be minimal of relatively no concern. When the dose surpasses the 150mg mark this will create a greater level of suppression, but there is no reason for any man to need a dose greater than 150mg per day. In theory, assuming your natural testosterone levels are in the high end optimal range, the individual could implement a cycle of Proviron and a moderate suppressive steroid at a low dose such as Anavar and forgo the need of exogenous testosterone supplementation. However, the Anavar dose would need to be very low and natural levels very high. Most men will still need exogenous testosterone, especially when we consider standard anabolic steroid cycles .