Halotestin is the brand name for fluoxymesterone, an oral anabolic-androgenic steroid. It is a synthetic testosterone-derived drug that has been prescribed medically for certain hormone-related conditions, but it is also known in bodybuilding circles because it can increase strength, aggression/drive, hardness, and muscle density without much water weight.
 
Medically, fluoxymesterone has been used for things like male hypogonadism, delayed puberty in some males, and rarely certain breast cancer situations, but it is not commonly used compared with safer options.
 
The big thing to know: Halotestin is considered one of the harsher oral steroids. It is 17-alpha-alkylated, meaning it survives oral digestion but puts more stress on the liver. Known risks include liver enzyme elevation, cholestatic jaundice, rare liver tumors/peliosis hepatis, acne, hair loss, mood changes, sodium/water retention, blood pressure issues, cholesterol worsening, increased red blood cell count, and cardiovascular strain.
 
For bodybuilding/contest prep, people usually talk about it as a short-term “hardening/strength” compound, not a true fat-loss drug. It does not directly burn fat. Any leaner or harder look is more from androgenic effects, training intensity, glycogen/water appearance, and dryness perception—not actual fat loss.