YK-11 — Dosing, Cycles, Half-Life & Side Effects
YK-11 is a selective androgen receptor modulator (SARM) with a half-life of 12 hours. AR partial agonist (19-norpregna-derived steroidal compound, often misclassified as a SARM) that induces follistatin expression in myoblasts (Kanno 2013) — indirectly antagonizing myostatin signaling. Not a direct myostatin inhibitor. No human PK study published; parent compound rapidly hydrolyzed in plasma. Primary risks include significant hepatotoxicity, strong HPTA suppression. This page is educational harm-reduction reference compiled from peer-reviewed literature — not medical advice, not an endorsement, not a recommendation to use. Consult a licensed clinician before any decision.
Quick Facts
| Class | Selective Androgen Receptor Modulator |
|---|---|
| Half-life | 12 hours |
| Detection window | 10 days |
| Aromatization | No |
| Hepatotoxicity | High |
| Suppression | 7/10 |
| 17α-alkylated | No |
| Administration | oral |
Typical Dosing Ranges
Common dose range: 5-10mg/day
Cycle length: 6-8 weeks
Time to steady state: ~1.5 days
Dose ranges are compiled from published pharmacokinetic studies and community-reported usage. Where a value is community-reported rather than clinically studied, this page and its structured data flag it. Lower end of any range is always the safer starting point.
Stacking Considerations
- No structural stacking blockers. Standard harm-reduction rules apply: minimize total androgen load, minimize oral exposure, and monitor bloodwork.
PCT Requirements
- This compound causes clinically meaningful HPTA suppression. Post-cycle therapy is recommended.
- Depot clearance estimate: ~2 days post-last-dose before SERM start (5 × apparent depot half-life of 8h).
- Never stack two SERMs. Extend a single SERM (tamoxifen OR enclomiphene/clomiphene) rather than combining.
- Use the cycle planner to generate a full protocol based on your complete stack, not this compound alone.
Side Effect Profile
- High suppression
- Liver toxic
- Limited research
- Expensive
Known Interactions
No compound-specific interactions are catalogued in the current matrix. This does not mean no risk exists — it means there is no curated pairwise entry.
Related compounds
Monitoring (Bloodwork & Vitals)
- Comprehensive metabolic panel (baseline, mid-cycle, post-cycle)
- Lipid panel (total cholesterol, HDL, LDL, triglycerides)
- CBC (hemoglobin, hematocrit — watch for erythrocytosis)
- Sex-hormone panel (Total T, Free T, Estradiol sensitive, SHBG, LH, FSH)
- Blood pressure (weekly self-check; flag systolic >140 or diastolic >90)
Baseline bloodwork is recommended before any cycle. Discontinue if liver enzymes exceed 3× upper limit of normal or if hematocrit exceeds 54%.
Frequently Asked Questions
What is the half-life of YK-11?
YK-11 has a half-life of approximately 12 hours. Clearance estimate: 8h × 5 = 40h = 1.5 days. This figure is used to determine injection frequency (for esters) and post-cycle clearance timing.
What is the typical dose range for YK-11?
Commonly reported ranges for YK-11: 5-10mg/day. Cycle length: 6-8 weeks. These are compiled from published studies and community-reported usage — individual response varies and lower end is always preferred.
Does YK-11 suppress natural testosterone?
YK-11 causes strong suppression of the HPTA axis (score 7/10). Post-cycle therapy (PCT) is recommended after use.
Is YK-11 liver toxic?
Hepatotoxicity rating: High. Non-17αα compound — liver stress is lower but still warrants periodic monitoring during a cycle.
Does YK-11 aromatize to estrogen?
Aromatization profile: No. Minimal to no aromatization expected, so aromatase inhibitors are not typically indicated for this compound alone.
What is YK-11 typically used for?
YK-11 is commonly used for: Bulking, Strength gains, Advanced users. Intended-use context does not imply safety — every use case carries the same underlying pharmacological risks.
Citations
- Piper T et al.. 2018. Drug Test Anal — Half-life estimated 6-10 hours from metabolite detection data; no formal PK study
- Dahleh SS et al.. 2024. Neurotoxicity study — Hippocampal oxidative stress and BDNF downregulation in rats; methylated steroidal structure implies liver stress
- Kanno Y et al.. 2011. Biol Pharm Bull — YK-11 characterized as AR partial agonist; activates AR without N/C interaction (gene-selective transactivation in MDA-MB-453 cells)
- Kanno Y et al.. 2013. Biol Pharm Bull — YK-11 induces follistatin in C2C12 myoblasts (indirect myostatin antagonism); effect blocked by anti-Fst antibody. NOT a direct myostatin inhibitor — corrects common mischaracterization
- Yatsu T et al.. 2018. Biol Pharm Bull — YK-11 stimulates osteoblast proliferation/mineralization via AR + Akt non-genomic signaling — osteogenic preclinical evidence
- Van Wagoner RM et al.. 2017. JAMA — 52% of SARM products contained labeled compound; YK-11 frequently mislabeled/unstable in supplement products (compounded by structural instability per Lee 2021)
- Gao W, et al. Selective androgen receptor modulator treatment improves muscle mass and strength. J Clin Endocrinol Metab 2005
Disclaimer
StackItSmart is an independent harm-reduction reference. The content above is compiled from peer-reviewed literature and is not medical advice, not an endorsement, and not a recommendation to use YK-11. Performance-enhancing compounds carry legal, endocrine, cardiovascular, and hepatic risks. Consult a licensed clinician before any decision. StackItSmart does not provide sourcing, procurement, or dosing prescriptions.