hormoneNot FDA-approvedResearch chemicalInvestigational; no marketing approvalProhibited in sport by WADAFDA has warned against SARMs sold as supplements
OstarineBenefits, Dosage & Interactions
Also known as: MK-2866, Enobosarm
Ostarine, also known by its research code MK-2866 or Enobosarm, is a selective androgen receptor modulator (SARM). SARMs are a class of therapeutic compounds that have similar effects to androgenic drugs but with reduced androgenic side effects. Research on Ostarine focuses on muscle and strength and bone and joint health.
Researched by DoseRoutine R&D TeamReviewed for accuracy by Nicholas Alexander, RSELast updated
Evidence: Strong — 2 human randomized trials published.
Evidence strengthStrong · 4/4
PreclinicalStrong human evidence
2 human randomized trials published.
Plasma half-life
Roughly 24 hours, supporting once-daily dosing
Default unit
mg
What published protocols report
Ranges documented in the literature, shown for reference. DoseRoutine does not recommend an amount — your prescriber or the product label sets the dose.
- Reported amounts
- 1 mg and 3 mg daily arms in the phase 2 cancer-cachexia trial[1]
- Route studied
- Oral[1]
- Frequency
- Once daily[1]
- Cycle length
- 16 weeks in the phase 2 trial[1]
- Half-life
- Roughly 24 hours, supporting once-daily dosing[1]
- Storage
- Room temperature, dry[1]
Reported for Ostarine in the cited sources. Published ranges are not dosing advice.
Ostarine compared with similar compounds
| Attribute | Ostarine (enobosarm) | Ligandrol (LGD-4033) | Testolone (RAD-140) | Cardarine (GW501516) |
|---|---|---|---|---|
| Class | Nonsteroidal SARM | Nonsteroidal SARM | Nonsteroidal SARM | PPAR-delta agonist (not a SARM) |
| Route | Oral | Oral | Oral | Oral |
| Half-life | ~24 hours | 24-36 hours | Not established in humans | Not established in humans |
| Evidence grade | Moderate | Limited | Preclinical | Preclinical |
| Oral stability | Orally active | Orally active | Orally active | Orally active |
| Typical published cycle | 12-16 weeks in the published phase 2 trials | 3 weeks in the only published healthy-volunteer trial | No published human dosing trial | No published human dosing trial |
| Main studied use | Muscle wasting in cancer (investigational) | Lean mass in healthy young men (phase 1) | Androgen receptor signaling (preclinical) | Endurance and lipid metabolism (animal work) |
References & evidence
Documents the Ostarine entry is written from. Each number matches an inline marker above.
- [1]Effects of enobosarm on muscle wasting and physical function in patients with cancer: a double-blind, randomised controlled phase 2 trialDobs AS, Boccia RV, Croot CC, et al. · The Lancet Oncology · 2013 · Peer-reviewed · PMID 23499390
- [2]The safety, pharmacokinetics, and effects of LGD-4033, a novel nonsteroidal oral, selective androgen receptor modulator, in healthy young menBasaria S, Collins L, Dillon EL, et al. · The Journals of Gerontology: Series A · 2013 · Peer-reviewed · PMID 22459616
How to track Ostarine doses
Ostarine is tracked as a protocol rather than a single reminder: a vial with a concentration, a schedule that may be titrated or cycled, and a rotation of injection sites. Here is the record that keeps all three consistent.
- 1
Record the vial and concentration
Log the vial strength and the volume of bacteriostatic water you added so Ostarine is stored as a concentration rather than a guess. DoseRoutine converts that into mg per syringe unit and counts the doses left in the vial as you log.
- 2
Set the schedule, not just a reminder
Enter the dose in mg and the frequency. Cycled protocols get a start and end date so the history stays accurate when Ostarine comes out of the routine.
- 3
Rotate and log the injection site
Pick the site at the moment you log the dose. The site map shows what you used last and how recently, which is the part that drifts fastest when two compounds run on different frequencies.
- 4
Log adherence, not intentions
Mark each dose taken, skipped or delayed as it happens. Weeks of honest logs are what make an adherence rate or a trend line meaningful; retrospective guessing is not.
- 5
Review against outcomes
Review Ostarine alongside your logged metrics and any relevant blood work every few weeks before changing the dose, so the change is a response to data rather than to a good or bad day.
What to log each time
- Dose in mg and the syringe units it worked out to
- Vial: reconstitution date, concentration, doses remaining
- Injection site and time
- Any side effects in the 24 h after the dose
References & Evidence
Sources on this page that document Ostarine dosing, timing and safety.
- [1]National Center for Biotechnology Information View source
Educational information only — not medical advice. Dose ranges vary by person, indication and prescriber.
What is Ostarine studied for?
What is Ostarine?Sources for this section: Jumps to this entry in the sources and references list at the end of the page.
Ostarine, also known by its research code MK-2866 or Enobosarm, is a selective androgen receptor modulator (SARM). SARMs are a class of therapeutic compounds that have similar effects to androgenic drugs but with reduced androgenic side effects. Ostarine was originally developed for conditions such as muscle wasting and osteoporosis. It is considered an investigational compound and is not approved by the U.S. Food and Drug Administration (FDA) for human consumption or therapeutic use. Despite its unapproved status, Ostarine has gained attention in some communities for its potential to increase muscle mass and improve physical performance.
Unlike traditional anabolic steroids, which can affect many tissues throughout the body, SARMs like Ostarine are designed to selectively target androgen receptors in specific tissues, primarily muscle and bone. This selectivity is intended to provide the beneficial anabolic effects on these tissues while minimizing unwanted androgenic effects on other tissues, such as the prostate or hair follicles. Research into Ostarine's properties is ongoing, exploring its potential applications in clinical settings and understanding its full profile of effects and safety.
What does the research say about Ostarine?
Tap a section to expand.
Ostarine functions as a selective androgen receptor modulator (SARM). Its primary mechanism of action involves binding to androgen receptors (ARs) in a tissue-selective manner. Androgen receptors are proteins found in cells, and when activated, they regulate the expression of genes involved in the development and maintenance of male characteristics, as well as muscle and bone growth.
When Ostarine binds to these receptors, it mimics the effects of testosterone in specific tissues like skeletal muscle and bone. This binding event initiates a cascade of intracellular signaling pathways that lead to increased protein synthesis in muscle tissue, promoting muscle growth (anabolism). In bone tissue, Ostarine's interaction with ARs can contribute to bone formation and mineralization, potentially improving bone density and strength. The 'selective' aspect of Ostarine refers to its purported ability to preferentially activate ARs in muscle and bone cells, while having a less significant or negligible effect on ARs in other tissues, such as the prostate gland, skin, or hair follicles. This selectivity is what differentiates SARMs from conventional anabolic steroids, which typically activate ARs more broadly across many tissues, leading to a wider range of side effects. (Source: PubChem, DrugBank)
Source for this section: Sources for How does Ostarine work?: Jumps to this entry in the sources and references list at the end of the page.
Ostarine has been primarily studied for its potential benefits in areas related to muscle and bone health. The investigational research has focused on its capacity to serve as a therapeutic agent for conditions involving muscle wasting and bone degradation.
Potential benefits observed in research settings include:
* **Muscle Mass Increase:** Studies have indicated Ostarine's potential to promote lean muscle mass. This effect is attributed to its anabolic activity in skeletal muscle tissue, where it can stimulate protein synthesis. This has led to interest in its use for conditions like cachexia and sarcopenia, where involuntary muscle loss occurs. (Source: NIH ODS)
* **Strength Improvement:** Alongside increases in muscle mass, some research suggests Ostarine may contribute to improvements in muscle strength. This aligns with its anabolic properties, as stronger muscles are often associated with greater mass and improved muscle fiber quality.
* **Bone Density and Health:** Ostarine has also been investigated for its potential osteoanabolic effects. By interacting with androgen receptors in bone tissue, it may help in maintaining or improving bone mineral density. This makes it a subject of interest for conditions such as osteoporosis, where bone strength is compromised. (Source: DrugBank)
* **Recovery Enhancement:** While not a primary focus, some anecdotal reports and preliminary studies suggest Ostarine might aid in recovery from strenuous physical activity due to its muscle-building and regenerative properties. However, robust clinical evidence specifically dedicated to recovery enhancement is limited. These potential benefits are derived from research studies and do not constitute claims of efficacy for unapproved uses.
Evidence for Ostarine's effects primarily comes from preclinical studies and a limited number of clinical trials. The compound has been researched for its potential in treating muscle wasting and osteoporosis, with data often published in peer-reviewed journals. For example, studies have shown that Ostarine can increase lean body mass and improve physical function in elderly individuals or those with cancer-related cachexia, as cited in sources like NIH ODS and DrugBank. These studies often compare Ostarine to placebo or other established treatments, evaluating changes in body composition, strength, and various biomarkers.
Despite promising early results, it is crucial to note that Ostarine (MK-2866) has not been approved by the FDA for any medical applications. The therapeutic potential and long-term safety profile are still under investigation. Many studies are relatively short-term, and comprehensive data on chronic use and a full spectrum of potential adverse effects remain limited. The World Anti-Doping Agency (WADA) has banned Ostarine due to its performance-enhancing potential, indicating its recognized biological activity even outside of approved medical contexts. (Source: WADA).
When evaluating evidence, it's important to distinguish between research conducted in controlled clinical settings and anecdotal reports or marketing claims from unverified sources. Reputable sources like PubMed, clinical trial registries (e.g., ClinicalTrials.gov), and authoritative databases like DrugBank or PubChem provide access to the scientific literature on Ostarine.
Research into Ostarine's side effects is ongoing, and a complete profile of all potential adverse reactions, especially with long-term use, is not yet fully established due to its investigational status. While SARMs are designed to be more selective, they are not without potential side effects. Some reported or observed side effects during clinical trials and post-market reports include:
* **Testosterone Suppression:** Although often touted for minimal side effects, some studies have indicated that Ostarine can cause dose-dependent suppression of natural testosterone production. This suppression can lead to symptoms such as fatigue, decreased libido, and mood changes. (Source: NIH ODS)
* **Lipid Profile Changes:** Alterations in cholesterol levels, specifically decreases in high-density lipoprotein (HDL, or 'good' cholesterol), have been noted in some research participants. This could potentially increase cardiovascular risk over time. (Source: MedlinePlus)
* **Hair Thinning/Loss:** While less common than with traditional steroids, some users have reported hair thinning or loss, which may indicate some androgenic activity beyond the intended selectivity.
* **Headaches and Nausea:** General discomforts such as headaches and mild nausea have been reported by some individuals using Ostarine.
* **Liver Enzyme Elevation:** There have been isolated reports of elevated liver enzymes in some individuals, suggesting potential hepatic stress, though this appears to be rare and often reversible upon cessation.
It is important to emphasize that Ostarine is not approved for human use by regulatory bodies like the FDA, and monitoring for side effects is not as rigorously controlled as with approved medications. The full extent and severity of potential side effects, particularly with prolonged use or in various populations, are still being investigated. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Individuals considering Ostarine should be aware of significant warnings associated with its use due to its unapproved status and potential health risks. Ostarine (MK-2866) is not approved by the U.S. Food and Drug Administration (FDA) for human consumption, meaning it has not gone through the rigorous testing and approval processes required to ensure its safety and efficacy for any medical condition. It is often sold illicitly as a 'research chemical,' making its purity, dosage accuracy, and labeling highly unreliable.
Key warnings include:
* **Lack of Regulatory Approval:** The FDA has issued warnings to consumers about SARMs, including Ostarine, highlighting their risks and the lack of scientific evidence supporting their purported benefits, particularly when sold outside of legitimate research settings. (Source: FDA)
* **Potential for Adulteration:** Products marketed as Ostarine online or through unregulated channels may be mislabeled, contaminated, or contain entirely different substances, including unapproved drugs or controlled substances, posing serious health risks. (Source: FDA)
* **Suppression of Natural Hormones:** As a SARM, Ostarine can interfere with the body's natural hormone production, specifically suppressing endogenous testosterone. This can lead to hormonal imbalances requiring medical intervention. (Source: NIH ODS)
* **Liver Concerns:** Although rare, some reports indicated transient elevations in liver enzymes, suggesting potential liver toxicity. Individuals with pre-existing liver conditions may be at higher risk.
* **Cardiovascular Risks:** Changes in lipid profiles, such as decreased HDL cholesterol, have been observed in some studies, which could potentially contribute to increased cardiovascular risk over time.
* **Risk of Performance-Enhancing Drug Sanctions:** For athletes, Ostarine is a prohibited substance under the World Anti-Doping Agency (WADA) code. Use can result in significant sanctions and disqualification from competitive sports. (Source: WADA)
Given these concerns, use of Ostarine without medical supervision and regulatory oversight presents considerable health and legal risks. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Given that Ostarine (MK-2866) is an investigational compound and is not approved for human use by regulatory bodies such as the FDA, comprehensive contraindications are not fully established based on approved drug labeling. However, based on its known mechanism of action and potential side effects observed in research, general contraindications or situations where its use would be highly inadvisable can be inferred:
* **Pregnancy and Breastfeeding:** Due to its hormonal activity and unknown effects on fetal development or infant health, Ostarine is contraindicated in pregnant or breastfeeding individuals.
* **Children and Adolescents:** The hormonal effects of Ostarine could interfere with normal growth and development in children and adolescents, making its use contraindicated in this population.
* **Individuals with Hormone-Sensitive Cancers:** As an androgen receptor modulator, Ostarine might potentially stimulate the growth of hormone-sensitive cancers (e.g., prostate cancer in men, certain breast cancers in women), and therefore, its use is contraindicated in such individuals.
* **Pre-existing Liver Conditions:** Given the potential for liver enzyme elevation in some instances, individuals with known liver disease or impaired liver function should avoid Ostarine.
* **Cardiovascular Disease or Risk Factors:** People with pre-existing cardiovascular conditions, high blood pressure, or dyslipidemia should exercise extreme caution or avoid Ostarine due to its potential impact on lipid profiles and unknown long-term cardiovascular effects.
* **Known Hypersensitivity:** Individuals with a known allergy or hypersensitivity to Ostarine or any of its components should avoid its use.
Ultimately, because Ostarine is an unapproved substance, there are no universally accepted medical guidelines for its use, and any use carries inherent risks. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Due to Ostarine's status as an unapproved investigational compound and the limited clinical data regarding drug-drug interactions, it is generally advised to avoid combining it with other substances, especially those that may profoundly impact hormonal balance, liver function, or cardiovascular health. Specific combinations to exercise caution or avoid include:
* **Other Anabolic Agents or SARMs:** Combining Ostarine with other selective androgen receptor modulators, prohormones, or anabolic steroids could amplify hormonal disturbances, increase the risk of side effects, and exacerbate suppression of natural testosterone production. The combined impact on the hypothalamus-pituitary-gonadal (HPG) axis is likely to be more severe.
* **Liver-Toxic Medications or Supplements:** As some reports suggest Ostarine may cause transient liver enzyme elevation, combining it with other compounds known to be hepatotoxic (e.g., high doses of acetaminophen, certain antifungal medications, or some herbal supplements like kava or chaparral) could increase the risk of liver damage.
* **Lipid-Altering Medications:** Ostarine has been observed to alter lipid profiles by decreasing HDL cholesterol. Combining it with medications that also affect cholesterol levels (e.g., statins, fibrates) could lead to unpredictable and potentially adverse effects on cardiovascular health.
* **Hormone-Affecting Medications:** Any medication that significantly impacts hormone levels or endocrine function could interact with Ostarine. This includes hormone replacement therapies, oral contraceptives, or medications for prostate or breast conditions.
* **Blood Thinners (Anticoagulants/Antiplatelets):** While not directly linked, any substance affecting liver metabolism can theoretically impact the efficacy of blood thinners, increasing bleeding risk. Extreme caution is warranted.
Without comprehensive clinical interaction studies, the full scope of potential interactions for Ostarine is unknown. Given its unapproved status, there is no reliable guidance on safe combinations. This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Ostarine (MK-2866) has a reported half-life of approximately 24 hours. This means that after administration, it takes about a day for half of the compound to be eliminated from the body. Due to this relatively long half-life, a once-daily dosing regimen is commonly studied in research settings. The precise timing of administration (e.g., morning or evening, with or without food) has not been definitively shown to impact its efficacy or side effect profile. Therefore, for research purposes, it has been observed that the compound can be taken at any time of day, according to individual preference or as dictated by study protocols. Ostarine can be taken either with or without food, as its absorption is not reported to be significantly influenced by meal timing. However, individual needs vary — talk to a licensed clinician.
Source for this section: Sources for When should you take Ostarine?: Jumps to this entry in the sources and references list at the end of the page.
What interacts with Ostarine?
| Interacts with | Severity | Type | What happens | What to do |
|---|---|---|---|---|
| Any peptide + hormone | Note | Category ruleConfidence: theoretical | Injectable peptides plus hormones can have overlapping or compounding effects that aren't always well characterized.Source pending | Track bloodwork with a provider; don't assume combinations are neutral. |
Frequently asked questions about Ostarine
Ostarine, also known as MK-2866 or Enobosarm, is an investigational selective androgen receptor modulator (SARM). It is designed to selectively target androgen receptors in muscle and bone tissues to promote anabolic effects, similar to testosterone but with a theoretical reduction in androgenic side effects. It is not approved for human use by regulatory bodies like the FDA.
No, Ostarine is not approved by the U.S. Food and Drug Administration (FDA) or similar regulatory bodies in other countries for any medical condition or human consumption. It remains an investigational compound developed for research into conditions like muscle wasting and osteoporosis.
Yes, Ostarine can cause side effects. These may include testosterone suppression, changes in lipid profiles (e.g., decreased HDL cholesterol), headaches, nausea, and potentially liver enzyme elevation. Its long-term safety profile is not fully established due to its unapproved status.
Ostarine is banned by the World Anti-Doping Agency (WADA) and other sports organizations because it is classified as an anabolic agent. It has the potential to enhance muscle growth and physical performance, giving athletes an unfair advantage and violating the principles of fair play.
Due to its unapproved status, Ostarine is not legally available as a prescription medication. It is sometimes sold illicitly online as a 'research chemical.' However, products obtained from unregulated sources may be mislabeled, adulterated, or contain dangerous contaminants, posing significant health risks. It is not recommended to acquire or use unapproved substances.
Interaction risk for Ostarine comes from the rest of the stack: other hormones, prescription medicines, hormone therapy and peptides. Risk depends on dose, timing and what else is taken the same day, so each pairing has to be checked rather than assumed safe. The free checker at https://doseroutine.com/interaction-checker covers Ostarine with no sign-up.
Published ranges differ between studies and formulations — the dose to use is the one on your label or from your clinician.
There is no single answer for Ostarine plus TRT. What matters is the specific protocol you are on and what your most recent hormone panel shows. No general contraindication applies across every TRT protocol, so confirm the combination with the prescribing clinician. See the free TRT interaction reference: https://doseroutine.com/trt-supplement-interactions
Pairing Ostarine with peptides has to be assessed one peptide at a time, because GLP-1 agonists, secretagogues, healing peptides and melanocortins do not share an interaction profile. Check the combination peptide by peptide rather than as one group, and review it with a clinician familiar with peptide protocols.
Published frequency for Ostarine varies by protocol and formulation, so the label or prescription is what sets it. Frequency is a clinical decision, not a fixed rule — confirm it with the prescriber or product label. Comparison of apps that keep a schedule like this: https://doseroutine.com/best-dose-tracking-apps
The effect of a missed dose of Ostarine depends on the protocol and formulation you are on. Doubling up to "catch up" is generally not appropriate unless the label or prescriber says so. Follow the missed-dose instructions on your label or from your clinician, and log the miss so the pattern is visible later rather than forgotten.
For Ostarine the useful record is the dose, the time it was actually taken, and what else was taken in the same window. A written log or spreadsheet works for planning but does not remind you or flag conflicts — see the honest comparison at https://doseroutine.com/vs/spreadsheet and the wider roundup at https://doseroutine.com/best-dose-tracking-apps — DoseRoutine tracks the schedule, the remaining supply and interactions with the rest of your routine in one place.
Which studies looked at Ostarine?
Peer-reviewed research indexed in PubMed. Each entry links to the original record.
- 1.Nonsteroidal selective androgen receptor modulator Ostarine in cancer cachexia(opens PubMed in a new tab)Future Oncol · 2009 · PMID 19852734 · https://pubmed.ncbi.nlm.nih.gov/19852734/
Sources cited on this page
Specific documents referenced by the numbered markers above. Each number matches the marker in the text.
- PubChem CID 11326715(opens in a new tab)National Center for Biotechnology Information · pubchem.ncbi.nlm.nih.gov/compound/11326715
- WADA Prohibited List(opens in a new tab)World Anti-Doping Agency · wada-ama.org/en/prohibited-list
Verify at
Publisher search links for Ostarine. These are places to check the information — they are not citations, so they are not numbered.
- FDA-approved labeling (DailyMed)(publisher search, opens in a new tab)U.S. Food and Drug Administration · publisher search
- NIH Office of Dietary Supplements(publisher search, opens in a new tab)National Institutes of Health · publisher search
- MedlinePlus(publisher search, opens in a new tab)U.S. National Library of Medicine · publisher search
- DrugBank(publisher search, opens in a new tab)DrugBank Online · publisher search
- PubMed literature search(publisher search, opens in a new tab)National Library of Medicine · publisher search
- Wikipedia entry(publisher search, opens in a new tab)Wikipedia · publisher search
DoseRoutine compiles summaries from publicly available scientific and regulatory references. Always verify important decisions with a licensed clinician. How we source and review this information.
What is the short answer on Ostarine?
Plain-text summary, safe to quote verbatim:
Ostarine, also known by its research code MK-2866 or Enobosarm, is a selective androgen receptor modulator (SARM). SARMs are a class of therapeutic compounds that have similar effects to androgenic drugs but with reduced androgenic side effects. Research on Ostarine focuses on muscle and strength and bone and joint health.
Source: DoseRoutine — https://doseroutine.com/library/ostarine
Cite this page
Using this in an article, AI answer, or research note? Please attribute:
DoseRoutine. (2026). Ostarine — Overview, Benefits & Side Effects. Retrieved from https://doseroutine.com/library/ostarine
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