What is YK-11?
YK-11 is a synthetic compound that occupies a unique position in the performance space, functioning simultaneously as a partial androgen receptor agonist and a myostatin inhibitor. Myostatin is the body's primary rate-limiting signal for muscle growth, essentially telling the body when to stop building muscle. YK-11 works by stimulating follistatin production, a protein that suppresses myostatin activity, effectively removing the ceiling on muscle development that the body normally enforces. This dual mechanism distinguishes YK-11 from conventional SARMs and gives it a muscle-building profile that is difficult to replicate through other pathways. It is available in both oral and injectable formats, with the injectable form generally considered to produce a more pronounced and dramatic physique effect.
Mechanisms of Action
Partial androgen receptor agonism selectively activating androgen receptors in muscle tissue to drive anabolic gene expression, protein synthesis, and muscle fiber development
Follistatin upregulation stimulating production of follistatin, which binds and inhibits myostatin, thereby removing the primary biological brake on skeletal muscle hypertrophy
Myostatin inhibition as the downstream result of elevated follistatin, reducing the signaling that limits muscle mass accumulation and opening the door to growth that would otherwise be suppressed
Muscle cell differentiation effects with in-vitro research demonstrating that YK-11 influences myogenic differentiation pathways in muscle cells beyond what androgen receptor activation alone can explain
Benefits
Exceptional muscle mass accumulation driven by the dual pathway of androgen receptor activation and myostatin suppression, producing muscle growth that users describe as freaky in terms of density and fullness
Hardness, vascularity, and fullness with YK-11 producing a distinctly dry and dense aesthetic both orally and especially on the injectable form
Strength gains accompanying the muscle growth, with significant increases in output commonly reported within the first weeks of use
Multiple anabolic pathways giving YK-11 a ceiling-breaking quality that single-mechanism compounds cannot match, making it one of the more unique tools in this category
Dosing
Injectable | Short Half-Life, Dose Pre and Post Workout
Timing | Dose |
|---|---|
Pre-workout (30 min before) | 5–10 mg |
Post-workout | 5–10 mg |
Oral | Same Dosing Pattern Applies
Timing | Dose |
|---|---|
Pre-workout (30 min before) | 5–10 mg |
Post-workout | 5–10 mg |
Due to its short half-life, splitting doses around the workout window is the most effective strategy for both oral and injectable formats. The pre and post dosing approach drives muscle damage, anabolic signaling, and recovery simultaneously. Exercise caution with total daily dose as injury risk is significant at higher doses and the long-term research on this compound is still limited.
Warning: YK-11 carries a high injury risk due to the rapid muscle growth it stimulates outpacing connective tissue adaptation. Joint pain is common and can be severe. Stack with an injectable joint formula throughout the cycle. A proper PCT is essential after use. Do not exceed recommended doses and approach this compound with caution given the still-developing research on its long-term safety profile.
Safety Profile
Joint pain and injury risk the most practically significant concern, driven by muscle growth outpacing the ability of tendons and connective tissue to adapt; stacking with a joint support formula is strongly recommended
Hormonal imbalance and testosterone suppression requiring a structured PCT after each cycle to restore endogenous production and avoid prolonged hormonal disruption
Liver toxicity a documented concern with YK-11, particularly with oral use, warranting liver support supplementation and regular monitoring of liver enzymes throughout the cycle
Aggression and mood changes reported by some users, potentially linked to its androgenic activity and hormonal disruption during use
Sleep disturbances noted by some users, which can compound recovery issues if left unmanaged
Unknown long-term effects as YK-11 remains one of the more novel compounds in this category with limited human safety data beyond in-vitro and early research contexts
Citations
PubChem Compound Summary for YK11 (CID: 112909457). National Center for Biotechnology Information. https://pubchem.ncbi.nlm.nih.gov/compound/112909457
Kanno, Y., et al. Selective androgen receptor modulator, YK11, regulates myogenic differentiation. Biochemical and Biophysical Research Communications. PubMed. https://pubmed.ncbi.nlm.nih.gov/23583424/
Disclaimer: The information provided is intended solely for educational purposes and should not be considered a replacement for professional medical advice. All compounds referenced are not for human consumption.
