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 . 
As with any medication, there are possible side effects or risks involved. Common risks from steroid injections include pain at the injection site, bruising due to broken blood vessels, skin discolouration and aggravation of inflammation. Rarer risks include allergic reactions, infection, tendon rupture and serious injury to bones called necrosis. Long term side effects (depending on frequency and dose) include thinning of skin, easy bruising, weight gain, puffiness in the face, higher blood pressure, cataract formation, and osteoporosis (reduced bone density). Steroid injections may be given every 3-4 months but frequent injections may lead to tissue weakening at the injection site and is not recommended. Side effects do not happen in everyone and vary from person to person.