Halotestin vs MK-2866
Well Studied vs Moderate Research
avoid Mechanism-based · 64% Both Halotestin and MK-2866 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
Halotestin MK-2866
Weight 336.44 Da 389.33 Da
Half-life ~9.5 hours ~24 hours
Type 9-fluoro-11-beta-hydroxy-17-alpha-methyltestosterone (C20H29FO3) Non-steroidal selective androgen receptor modulator (C19H14F3N3O3)
Key Benefits
Halotestin
01 Dramatic increase in strength and power output without water retention
02 Pronounced increase in aggression and competitive drive
03 Does not aromatize to estrogen, producing a hard and dry appearance
04 Enhances red blood cell production and oxygen-carrying capacity
05 Rapid onset of effects, typically noticeable within days
06 Uniquely suited for pre-competition or pre-meet peaking protocols
07 Short cycle duration limits cumulative exposure
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
Side Effects
Halotestin
Severe hepatic stress (elevated ALT, AST, GGT, bilirubin)
Pronounced aggression and irritability
HDL cholesterol suppression and LDL elevation
Elevated blood pressure
Headaches (frequently reported, may be related to blood pressure changes)
Suppression of endogenous testosterone production
Oily skin and acne
Decreased appetite (potentially related to liver stress)
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
Contraindications
Known or suspected prostate cancer
Breast cancer in males
Pregnancy (Category X - causes fetal harm)
Active liver disease or existing hepatic impairment
Severe cardiovascular disease or uncontrolled hypertension
Hypercalcemia
Nephrosis or nephrotic phase of nephritis
History of cholestatic jaundice or hepatic dysfunction from prior anabolic steroid use
Hypersensitivity to fluoxymesterone or any formulation component
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
Research Evidence
Halotestin MK-2866
Status Well Studied Moderate Research
References 5 studies 5 studies
Latest October 2023 —
FDA Approved Yes No
This comparison is for educational and research purposes only. Consult a healthcare professional before use.