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 . 
Although anabolic androgenic steroids like Boldenone may increase lean muscle mass, strength, and the ability to train longer and harder, the serious side effects of steroids are many and may not be reversible. The minor side effects of steroid use include acne, oily skin, excess hair growth, and deepening of the voice. The major side effects of steroid use include an increased risk of cancer, increased risk of heart and liver disease, jaundice, fluid retention, reduction in HDL-C (“good cholesterol”), high blood pressure, changes in blood coagulation, increased risk of atherosclerosis, swelling of the soft tissues of the extremities (edema), and obstructive sleep apnea.
If you are a tested athlete, if you’re going to supplement with anabolic steroids you must understand steroid detection times thoroughly if you stand a chance. For the tested athlete, you will be somewhat limited in-regards to which steroids you can use. For example, if you’re a truly tested athlete, Nandrolone based steroids can never be used as their detection time stretches past a year. Many testosterone compounds must also be avoided; especially large esters or testosterone mixtures, but the smaller or ester free versions are often an option. Of course, many athletes who are tested are only done so for show, and if that’s the case, well, it really doesn’t matter what you use. In any case, for show or a legitimate test, if you understand steroid detection times there’s really no reason for you to have a problem.