Overview
Ostarine is a selective androgen receptor modulator (SARM) — a class of compounds that selectively bind to androgen receptors in muscle and bone tissue. Selective androgen receptor modulator.
With a half-life of ~1 days (24 hours), Ostarine supports less frequent dosing schedules. Taken orally, it has a bioavailability of approximately 95% via its primary route.
Half-life approximately 24 hours. High oral bioavailability. One-compartment model. Not FDA-approved for human use.
Mechanism of Action
Ostarine's pharmacological activity involves the following key pathways:
Selective Receptor Binding
Ostarine is designed to selectively bind to androgen receptors in muscle and bone tissue, with reduced activity in other androgen-sensitive tissues.
Tissue Selectivity
The selectivity of Ostarine is achieved through differential coactivator recruitment — the compound activates different downstream pathways depending on the tissue type.
Dosing Protocols
The following protocols represent commonly observed dosing patterns. These are observational summaries, not recommendations.
Dose
10 mg/day
Route
Oral
Frequency
Every other day
Duration
8-12 weeks
Dose
25 mg/day
Route
Oral
Frequency
Every other day
Duration
8-12 weeks
Frequently Asked Questions
What is Ostarine MK-2866 and how does it work?
Ostarine (MK-2866), also known as Enobosarm, is a non-steroidal selective androgen receptor modulator (SARM) that binds to androgen receptors with tissue-selective activity. Unlike anabolic steroids, it preferentially activates androgen receptors in muscle and bone tissue while showing partial agonist or antagonist activity in other tissues. This selectivity is the defining characteristic of SARMs as a compound class.
What is the half-life of Ostarine MK-2866?
Ostarine has an elimination half-life of approximately 24 hours, allowing for convenient once-daily dosing. Steady state blood concentrations are typically reached within 5 days of consistent daily administration. The long half-life ensures stable plasma levels throughout the day without the need for split dosing.
What are the common dosing protocols for Ostarine?
The most commonly observed doses in community protocols range from 10–25 mg per day taken orally. For cutting or body recomposition purposes, 10–15 mg daily is typical, while 20–25 mg daily is more commonly associated with lean mass gain goals. In clinical research, doses as low as 1–3 mg daily produced statistically significant improvements in lean body mass.
How long does it take for Ostarine to show results?
With a 24-hour half-life, Ostarine reaches steady state within approximately 5 days. Increased training endurance and stamina have been reported within the first 1–2 weeks. Visible changes in body composition — such as improved muscle definition and fullness — are commonly observed from week 3–4 onward, with full results typically manifesting across a 6–8 week cycle.
Does Ostarine suppress natural testosterone production?
Ostarine can cause dose-dependent suppression of natural testosterone production, though generally to a lesser degree than anabolic steroids. Higher doses and longer cycle durations are associated with greater suppression. Post-cycle recovery protocols of 4 weeks are commonly observed following standard Ostarine cycles. Bloodwork before and after a cycle is the most reliable way to assess individual hormonal impact.
What compounds are commonly stacked with Ostarine?
For cutting protocols, Ostarine is frequently paired with Cardarine (GW-501516) to support endurance alongside lean mass preservation. For lean bulking, it is sometimes combined with LGD-4033 (Ligandrol) or MK-677 (Ibutamoren). Ostarine is also used as a standalone compound, particularly for recomposition goals where simultaneous fat loss and muscle gain are the objective.