Buy Pure Bulk Testosterone Undecanoate Powder Online CAS 5949-44-0 What is Testosterone Undecanoate? Testosterone undecanoate is a synthetic androgen ester which acts as a prodrug of testosterone, and hence is considered to be a natural and bioidentical form of testosterone. Unlike other testosterone esters, testosterone undecanoate is available in both oral and intramuscular formulations. As an intramuscular injection, it is much longer-acting …