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.
The oral bioavailability of oxandrolone is 97%.  Its plasma protein binding is 94 to 97%.  The drug is metabolized primarily by the kidneys and to a lesser extent by the liver .   Oxandrolone is the only AAS that is not primarily or extensively metabolized by the liver, and this is thought to be related to its diminished hepatotoxicity relative to other AAS.   Its elimination half-life is reported as to hours but is extended to hours in the elderly.   Approximately 28% of an oral dose of oxandrolone is eliminated unchanged in the urine and 3% is excreted in the feces . 
There’s also the possibility that testosterone injections can actually worsen some of the symptoms they are intended to treat. This is because the body will often respond to extra testosterone by assuming that it doesn’t need to produce more itself. Thus your testes will slow down their natural production of the hormone and you will actually end up with a lower ‘baseline’ when you aren’t receiving the injections. On the other hand, if all goes well you might see some side effects associated with a sudden peak in testosterone which include acne, hair loss, and short temper.