Metandienone, also known as methandienone or methandrostenolone and sold under the brand name Dianabol (D-Bol) among others, is an androgen and anabolic steroid (AAS) medication which is still quite often used because of its affordability and effectiveness for bulking cycles.[4][5][1][6] It is also used non-medically for physique- and performance-enhancing purposes.[1] It is often taken by mouth.[1]

Side effects of metandienone include symptoms of masculinization like acne, increased hair growth, voice changes, and increased sexual desire, estrogenic effects like fluid retention and breast enlargement, and liver damage.[1] The drug is an agonist of the androgen receptor (AR), the biological target of androgens like testosterone and dihydrotestosterone (DHT), and has strong anabolic effects and moderate androgenic effects.[1] It also has moderate estrogenic effects.[1]

Metandienone was originally developed in 1955 by CIBA and marketed in Germany and the United States.[1][7][4][8][9] As the CIBA product Dianabol, metandienone quickly became the first widely used AAS among professional and amateur athletes, and remains the most common orally active AAS for non-medical use.[10][8][11][12] It is currently a controlled substance in the United States[13] and United Kingdom[14] and remains popular among bodybuilders. Metandienone is readily available without a prescription in certain countries such as Mexico, and is also manufactured in some Asian countries.[6]