MK-2866 vs Proviron
Moderate Research vs Well Studied
avoid Mechanism-based · 64% Both MK-2866 and Proviron carry hepatotoxic risk. Combining hepatotoxic compounds significantly increases liver damage potential. If unavoidable, include liver support (TUDCA/NAC) and monitor ALT/AST frequently.
Molecular Data
MK-2866 Proviron
Weight 389.33 Da 304.47 Da
Half-life ~24 hours ~12 hours
Type Non-steroidal selective androgen receptor modulator (C19H14F3N3O3) DHT derivative (C20H32O2)
Key Benefits
MK-2866
01 Increases lean body mass in a dose-dependent manner with clinical trial support
02 Preserves muscle mass during caloric deficit or catabolic conditions
03 Selective tissue activity reduces androgenic side effects compared to anabolic steroids
04 Oral bioavailability eliminates the need for injections
05 Does not aromatize to estrogen, avoiding gynecomastia and water retention
06 Improves physical function and stair-climbing power in clinical populations
07 Long 24-hour half-life allows convenient once-daily dosing
08 Mild side effect profile at commonly studied doses
Proviron
01 Strong SHBG binding frees more circulating testosterone, enhancing TRT efficacy
02 Improved mood, motivation, confidence, and overall sense of well-being
03 Significant enhancement of libido and sexual function
04 Anti-estrogenic effect reduces the need for dedicated aromatase inhibitors
05 Harder, drier, more defined physical appearance without water retention
06 Minimal hepatotoxicity due to absence of 17-alpha alkylation
07 May improve sperm quality at low doses in subfertile men
08 Rapid onset of subjective well-being effects (often within days)
Side Effects
MK-2866
Mild testosterone suppression (dose-dependent, typically 10-30% reduction at 25 mg)
HDL cholesterol reduction (10-20% suppression observed in clinical trials)
Headaches, particularly during the first 1-2 weeks
Mild back pain or muscle cramps
Transient fatigue toward the end of longer cycles
Slight reduction in libido at higher doses or extended cycle lengths
Proviron
Accelerated hair thinning or loss in those predisposed to male pattern baldness (DHT-mediated)
Mild suppression of endogenous testosterone at higher doses (though less suppressive than most AAS)
Oily skin and increased sebum production
Mild HDL cholesterol suppression with extended use
Increased body hair growth
Contraindications
Active liver disease or significantly elevated liver enzymes
Hormone-sensitive cancers (breast, prostate) without oncologist clearance
Pregnancy or breastfeeding (potential endocrine disruption to fetus/infant)
Individuals under 21 years of age (risk of premature HPTA disruption during development)
Concurrent use of hepatotoxic medications without liver function monitoring
Known hypersensitivity to MK-2866 or any formulation excipients
Competitive athletes subject to WADA or USADA anti-doping testing
Prostate cancer (active or history of androgen-sensitive prostate cancer)
Severe liver impairment (though hepatotoxicity risk is minimal)
Breast cancer in males
Hypersensitivity to mesterolone or any excipients
Women who are pregnant or may become pregnant (androgenic effects on fetus)
Research Evidence
MK-2866 Proviron
Status Moderate Research Well Studied
References 5 studies 5 studies
FDA Approved No No
This comparison is for educational and research purposes only. Consult a healthcare professional before use.