Ostarine (MK-2866) — Dosing, Cycles, Half-Life & Side Effects

Ostarine (MK-2866) is a selective androgen receptor modulator (SARM) with a half-life of 24 hours. WARNING: FDA has issued safety warnings about SARM-associated liver injury. Selective androgen receptor modulator for lean muscle. Not approved for human use - research chemical only. Suppression is dose-dependent and often more significant than marketed. 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

ClassSelective Androgen Receptor Modulators
Half-life24 hours
Detection window30 days
AromatizationNo
HepatotoxicityLow-Medium
Suppression3/10
17α-alkylatedNo
Administrationoral

Typical Dosing Ranges

Common dose range: 10-25mg/day (note: suppression increases significantly at higher doses)

Cycle length: 8-12 weeks

Time to steady state: ~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

  • Depot clearance estimate: ~5 days post-last-dose before SERM start (5 × apparent depot half-life of 24h).
  • 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

  • FDA WARNING: SARM-associated liver injury reported
  • Suppression is dose-dependent (significant at higher doses)
  • Not approved for human use
  • Limited human studies
  • WADA prohibited
  • Expensive
  • Detection time up to 9 days

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 Ostarine (MK-2866)?

Ostarine (MK-2866) has a half-life of approximately 24 hours. Clearance estimate: 24h � 5 = 120h = 5 days. This figure is used to determine injection frequency (for esters) and post-cycle clearance timing.

What is the typical dose range for Ostarine (MK-2866)?

Commonly reported ranges for Ostarine (MK-2866): 10-25mg/day (note: suppression increases significantly at higher doses). Cycle length: 8-12 weeks. These are compiled from published studies and community-reported usage — individual response varies and lower end is always preferred.

Does Ostarine (MK-2866) suppress natural testosterone?

Ostarine (MK-2866) causes moderate suppression of the HPTA axis (score 3/10). PCT may still be advisable depending on stack and duration.

Is Ostarine (MK-2866) liver toxic?

Hepatotoxicity rating: Low-Medium. Non-17αα compound — liver stress is lower but still warrants periodic monitoring during a cycle.

Does Ostarine (MK-2866) aromatize to estrogen?

Aromatization profile: No. Minimal to no aromatization expected, so aromatase inhibitors are not typically indicated for this compound alone.

What is Ostarine (MK-2866) typically used for?

Ostarine (MK-2866) is commonly used for: EXPERIMENTAL - Not approved for human use, Research purposes only. Intended-use context does not imply safety — every use case carries the same underlying pharmacological risks.

Citations

  1. Coss CC et al.. 2016. Invest New Drugs — Half-life 22.0 +/- 5.8 hours (range 13.7-31.3h)
  2. Dalton JT et al.. 2011. J Cachexia Sarcopenia Muscle — Total T suppressed dose-dependently but FSH/LH not significantly changed at clinical doses over 86 days
  3. Liu E et al. (SARM class extrapolation). 2025. Subst Use Misuse — Ostarine HDL suppression documented; CV profile comparable to other SARMs; supports cardioStrain 2/10
  4. Gao W, et al. Selective androgen receptor modulator treatment improves muscle mass and strength, and reduces bone turnover in older men. J Clin Endocrinol Metab 2005
  5. FDA Safety Statement: 'SARMs have been linked to serious safety concerns including increased risk of heart attack, stroke, and liver damage'

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 Ostarine (MK-2866). 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.

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