As alluded to above, one very important thing to acknowledge when using AAS (whether taking one hormone, stacking or cycling) is the risk of harmful side effects. Within a steroid cycle, the users will often stack other non-anabolic hormones into their program to maximize specific cycle objectives for example: the addition of drugs like Clenbuterol and/or Cytomel /T3 augment cutting/definition cycles; others called aromatase inhibitors (estrogen reducing drugs) like Letrozole . Letro and Anastrozole Arimidex are often included to inhibit the conversion of excess testosterone to negatively cycle impacting estrogen and; incorporating post-cycle therapy (PCT) drugs such as the synthetic estrogens Tamoxifen . Nolvadex , or Clomiphene Citrate . Clomid (which act as anti-estrogens in the male body), can be used alone, together, or in conjunction with those like Mesterolone . Proviron and Human Chorionic Gonadotropin ( HCG ) during PCT to bridge the gap between the end of a steroid cycle (synthetic testosterone usage) and the restoration of the bodys natural testosterone production. These drugs too must be researched, and controlled in similar fashion to AAS. Thus, steroid cycles can be as simple or complex as the users individualized goals, cycle histories and levels of understanding. Below are three samples of AAS stacked cycles of varying complexity along with a beginning PCT sample, and an explanation of goal intention & rationale for the selected compounds, dosages & durations. These illustrations and commentaries will provide a better understanding of what stacking and cycling are along with the many nuances they require.
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 . 
Anabolic steroids differ in their characteristics, which means there are steroids that are only suitable for specific uses. For instance, Trenbolone is not recommended for bulking but it is an outstanding fat burner. This makes it perfect for a lean mass cycle or a cutting cycle. Always take the side effects of a particular compound into consideration whenever you plan a stack. Do not combine anabolic steroids that show similar side effects. For example, never combine Anapolon and Dianabol because they are already quite toxic and if you combine them, the toxicity will increase exponentially and cause serious damage to your body.