The most commonly used AAS in medicine are testosterone and its various esters (but most commonly testosterone undecanoate , testosterone enanthate , testosterone cypionate , and testosterone propionate ),  nandrolone esters (most commonly nandrolone decanoate and nandrolone phenylpropionate ), stanozolol , and metandienone (methandrostenolone).  Others also available and used commonly but to a lesser extent include methyltestosterone , oxandrolone , mesterolone , and oxymetholone , as well as drostanolone propionate , metenolone (methylandrostenolone), and fluoxymesterone .  Dihydrotestosterone (DHT; androstanolone, stanolone) and its esters are also notable, although they are not widely used in medicine.  Boldenone undecylenate and trenbolone acetate are used in veterinary medicine . 
If you planning to buy anabolic steroids online , you must understand about the chemical structure and formula behind the manufacture of steroids to avoid side effects, that's why you should do a post cycle therapy after your steroids cycle . The steroids are synthetic hormones which can enhance the potential of body to stop muscle breakdown and prevent faster growth of muscles. Athletes usually take steroids to improve aggression, speed, stamina and strength. Athletes use steroids to lift heavier weights, run faster, jump higher and improve their power while performing in competitions.