Last updated: March 2026
Fluoxymesterone (Halotestin) carries one of the highest androgenic ratings of any AAS — roughly 8.5× testosterone. Historically used by powerlifters before competition for aggression and strength, it is also among the most hepatotoxic oral AAS. This educational reference covers its extreme pharmacology, documented risks, and harm reduction context.
Fluoxymesterone is a 17α-alkylated testosterone derivative with both a 9α-fluoro and 11β-hydroxy substitution, making it one of the most potent androgens ever synthesized — and one of the most toxic.
The 9α-fluoro and 11β-hydroxy modifications dramatically increase androgen receptor binding affinity and cannot be aromatized or 5α-reduced (or minimally so). This means essentially all androgenic activity is direct — no conversion to estrogen, no conversion to DHT needed. The result: extreme androgenic effects with minimal estrogenic side effects but severe androgenic ones (acne, aggression, hair loss, virilization).
Fluoxymesterone uniquely activates androgen receptors in the central nervous system — particularly the amygdala, hypothalamus, and prefrontal cortex. This produces the characteristic aggression, pain tolerance increase, and competitive drive that powerlifters sought. Clinical literature documents both desired competitive focus and problematic violent aggression. This CNS effect is dose-dependent and unpredictable at individual level.
Despite its extraordinary anabolic:androgenic ratio of ~1900:850, fluoxymesterone does NOT significantly aromatize to estrogen. Estrogenic side effects (water retention, gynecomastia) are minimal. However, this also means the "buffer" that estrogen provides for cardiovascular and bone health is absent. HDL cholesterol is severely suppressed.
As a 17α-alkylated compound at extreme androgenic potency, fluoxymesterone causes rapid and severe hepatic stress. ALT/AST elevation is expected even at low doses. Peliosis hepatis — blood-filled cysts in the liver — has been documented. Hepatocellular carcinoma risk increases with cumulative exposure. Cycle lengths exceeding 4 weeks are considered extremely dangerous.
Data from clinical trials, powerlifting literature, and pharmacological studies on fluoxymesterone.
If using any 17α-alkylated compound — especially one as potent as Halotestin — liver support and frequent bloodwork are non-negotiable harm reduction measures.
Dosing schedules, interaction warnings, and cycle protocols for 50+ compounds — all in one place.
This page is for educational and harm reduction purposes only. It is not medical advice. Fluoxymesterone (Halotestin) is a Schedule III controlled substance in the United States. It is banned by WADA and all major sports organizations. Halotestin carries EXTREME health risks including severe hepatotoxicity (peliosis hepatis, hepatocellular carcinoma), cardiovascular damage, and documented psychological effects including violent aggression. This compound is contraindicated in women. MeetPeptide does not endorse or encourage the use of controlled substances. Consult a qualified physician before any decisions regarding hormone use.