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 . 
Winstrol is hepatotoxic, and because of this, it should be used at the lowest effective dose for the shortest possible cycle. What’s more, you should consider using a supplement designed to provide some additional protection. Milk thistle is a highly recommended option; studies suggest it can provide an effective layer of protection when it is used for the entire length of your cycle. There are some other supplements on the market, such as Liver Care, which are blends of natural ingredients that have been shown to work together to prevent liver toxicity.