Users have reported pretty strong suppression of natural testosterone levels while using Oral Turinabol. This steroid is liver toxic but likely only slightly more toxic than equal doses of methandrostenolone. This steroid is well-known for its role in the state-sponsored doping program of the former East German Olympic doping program. This drug was given to male and female athletes specifically to increase athletic performance in the Olympics. Though men were also treated, women were the focus because they responded much better to treatment. Doses of only 10 to 20 mg per day produced marked increases in performance in women. This program also included other drugs like mestanolone, the 11-beta hydroxy form of Oral Turinabol, 4-chloro-methyltestosterone, 4-chloro-mestanolone, methandrostenolone, testosterone and nandrolone esters as well as some stimulants and peptide hormones. Even so, Oral Turinabol was the focus because it seemed to report the best results 4 .
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.