The melanocortin peptide used for sunless tanning and libido enhancement — powerful results, but a side-effect profile that demands careful titration.
Melanotan II (MT-II) is a synthetic analog of alpha-melanocyte-stimulating hormone (α-MSH) that non-selectively activates multiple melanocortin receptors — MC1R (pigmentation), MC3R/MC4R (appetite, libido), and MC5R (exocrine).
Originally developed at the University of Arizona to help reduce skin cancer risk by inducing protective pigmentation without UV exposure. It never completed clinical development but became popular as a tanning peptide, with PT-141 (bremelanotide) being a selective MC4R derivative that was eventually approved as Vyleesi.
Not FDA approved. Not WADA prohibited. Banned in several countries; available as research chemical elsewhere.
Activates melanocytes to produce eumelanin (brown/black pigment), darkening skin over 2–4 weeks of regular dosing. Important: UV exposure is still required to trigger the pigmentation response — MT-II amplifies your tan, it doesn’t replace sun/UV entirely.
Same mechanism as PT-141 — suppresses appetite and increases sexual desire/arousal via central nervous system pathways.
Non-selective activation of these receptors accounts for most of the side effect profile (nausea, flushing, darkening of moles and freckles).
| Benefit | Evidence |
|---|---|
| Skin pigmentation | Arizona studies: reliable induction of eumelanin production; dramatic darkening with continued use + UV exposure |
| Libido / sexual arousal | Same MC4R mechanism as PT-141; both male and female effects |
| Appetite suppression | Noticeable reduction in hunger; sometimes used adjunctively for weight loss |
| UV damage reduction | Induced pigmentation offers some photoprotection (but doesn’t replace sunscreen) |
MT-II is the less-selective parent of PT-141. If you want the libido effect without pigmentation changes, PT-141 is the cleaner option.
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeDo not skip the starter dose. First-time nausea can be intense.
10 mg vial + 2 mL BAC water = 5 mg/mL = 5000 mcg/mL
| Dose | Volume | Syringe Units |
|---|---|---|
| 250 mcg (starter) | 0.05 mL | 5 units |
| 500 mcg | 0.10 mL | 10 units |
| 1 mg | 0.20 mL | 20 units |
10 mg vial at 1 mg/day = 10 days; at 1 mg 2×/week maintenance = 5 weeks
Use our free peptide calculator to figure out your reconstitution volume, draw amount, and syringe units.
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MT-II has a notable side-effect profile — often the reason users switch to the more selective PT-141 for libido-only goals.
Case reports document rhabdomyolysis, acute kidney injury, and renal infarction following MT-II use — particularly at high doses. One case (PMID 23121206) reported a single 6 mg SubQ dose producing BP 151/85, HR 146, and rhabdomyolysis. A separate case series (PMID 31953620) documented thrombotic/renal complications.
Doses above the recommended range can trigger severe sympathomimetic toxicity — tachycardia, hypertension, and muscle breakdown. Do not chase faster results with larger doses. If you experience dark urine, severe muscle pain, chest pain, or a racing heart, seek emergency care.
Any new mole, changing mole, or mole with irregular borders while on MT-II warrants immediate dermatologist evaluation. Several case reports link MT-II use to melanoma progression.
MT-II is unregulated and almost exclusively purchased through grey-market online channels (PMID 30142729). Counterfeit and falsified biotechnology peptide drugs are a documented global safety threat (PMID 30165334) — contamination, incorrect potency, and substitution with other compounds are all real risks. Product purity cannot be verified without third-party testing; buy only from suppliers that publish current certificates of analysis, and accept that all use is at your own risk.
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Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeDisclaimer: This guide is for educational and informational purposes only and is not intended as medical advice, diagnosis, or treatment. The compounds discussed are not FDA approved for human use. Always consult a qualified healthcare provider before starting any new supplement or peptide protocol. StackTrax does not sell peptides or supplements directly — purchase links go to third-party vendors. StackTrax is not responsible for the products, quality, or business practices of any third-party vendor. This page contains affiliate links — StackTrax may earn a commission on purchases at no extra cost to you.
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StackTrax guides cover peptides and compounds that are not FDA-approved for the uses discussed. The dosing, reconstitution, and safety information is compiled from published research and community protocols for educational purposes only.
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