What it is
Melanotan II (MT-II) is a synthetic cyclic peptide analogue of alpha-melanocyte-stimulating hormone (alpha-MSH). It is a non-selective melanocortin receptor agonist, activating MC1R (skin pigment), MC4R (appetite and sexual function) and others. Acting on MC1R, it drives melanocytes to produce more melanin, which is why it darkens skin. It has never been approved for human use anywhere, and several regulators have specifically warned against it.
That non-selectivity is the core of both its effects and its problems: it does not just tan, it hits appetite, sexual and cardiovascular pathways at the same time.
What people use it for
The main reason people use it is tanning, often a deeper tan with less sun exposure. Secondary effects people notice or seek include appetite suppression and increased libido or spontaneous erections, all downstream of the same broad melanocortin activation. None of these is an approved or quality-controlled use.
Typical dose range
Early human research found tanning effects in the rough range of 1 to 2 mg per day. Community protocols usually split into a lower-dose “loading” phase to build pigment, then a smaller “maintenance” dose once or twice a week, with starting doses kept low specifically to limit nausea and flushing during titration. Larger body mass is sometimes cited as a reason for the higher end of the range.
Be deliberate about this: side effects scale with dose, and the case reports of serious harm (below) involved both single larger doses and ongoing use. Lower and slower is the harm-reduction default. If reconstituting, get the maths right rather than guessing: Peptide Calculator - Reconstitution & Dosage | Buy Peptides UK
Half-life and frequency
The plasma half-life is roughly 1 to 2 hours, so the peptide itself clears the bloodstream quickly. The pigmentation effect, however, lasts far longer (days), because it depends on melanin production rather than the drug staying present. That is why maintenance dosing can drop to once or twice weekly once a base tan is established, rather than daily.
Reconstitution (typical)
Supplied as a lyophilised powder. Standard handling: bring the vial to room temperature, add bacteriostatic water slowly down the inside of the vial, and swirl gently to dissolve rather than shaking. Pick your target concentration before adding water so each dose is a sane, measurable volume: Peptide Calculator - Reconstitution & Dosage | Buy Peptides UK. Avoid nasal-spray preparations; dosing through a spray is imprecise and several of the worst case reports involved unregulated sprays.
Storage
Lyophilised vial: store cold and dark, frozen at around -20 C for long-term storage. Reconstituted solution: refrigerate at 2 to 8 C, keep out of light, use within about 28 days, and do not freeze it (freeze-thaw cycles degrade the peptide).
Common side effects
The frequent, dose-titration effects are:
- Nausea (often the limiting factor early on)
- Facial flushing
- Appetite suppression
- Yawning and stretching, sometimes with spontaneous erections
- Fatigue or light-headedness
Skin and mole changes deserve their own emphasis, because they are the reason careful skin watching matters with this compound. MT-II activates melanocytes everywhere, not just where you want a tan. Expect existing moles and freckles to darken, freckles to multiply, and new pigmented spots to appear, sometimes within a day of dosing. Any mole that changes shape, grows, develops irregular borders or uneven colour, itches or bleeds should be assessed by a clinician promptly. Because MT-II makes pigmented lesions change, it can both mimic and mask the warning signs of skin cancer, so a baseline mole check and ongoing self-monitoring are sensible, and a dermatologist skin review is the cautious move.
Serious adverse effects have been reported in the medical literature, generally with higher doses, prolonged use, or unregulated product. These include refractory priapism (a painful, prolonged erection that is a medical emergency), marked blood-pressure elevation, rhabdomyolysis (muscle breakdown) with acute kidney injury, renal infarction, and posterior reversible encephalopathy syndrome. There are also case reports of melanoma in users, including a mucosal melanoma after nasal-spray use. The evidence that MT-II directly causes melanoma is not conclusive, and some of the excess may reflect more UV exposure in users, but the combination of “changes your moles” and “encourages more sun” is exactly the wrong mix for skin cancer risk.
Stacking and co-solubility
MT-II is sometimes stacked with PT-141, since both are melanocortin agonists; note that this compounds the shared side effects (nausea, flushing, blood pressure, priapism risk) rather than offering a clean addition, and there is no human safety data for the combination. Stacking with any other blood-pressure-active or vasoactive substance raises cardiovascular and priapism risk. If combined at all, peptides are drawn from separate vials, not co-mixed. From a harm-reduction view, this is not a compound that rewards aggressive stacking.
Evidence grade (human RCT / small human / animal-only / anecdote)
Weak and unfavourable on balance.
- Tanning effect: small human studies. Early controlled human work did show MT-II and related analogues produce skin darkening, so the core effect is real.
- Safety: dominated by case reports and adverse-event reports rather than controlled safety trials. This is a low tier of evidence, but the pattern of serious case reports across multiple organ systems is itself a meaningful red flag.
- Long-term and melanoma risk: unresolved. Reviews have not proven causation for melanoma, but they have not cleared it either, and the biological plausibility plus case reports keep it an open, serious concern.
- Most user reports of dosing and outcomes: anecdote.
In short, the tanning effect is genuine but the compound is unapproved, the safety data is built largely from things going wrong, and the skin-cancer question is open. That asymmetry matters.
Honest unknowns
- Whether MT-II independently increases melanoma risk is not settled; the honest position is “plausible and not ruled out”, not “proven safe”.
- The long-term cardiovascular and renal consequences of repeated use are not characterised by proper studies.
- Safe long-term dose and frequency are unknown; the popular loading/maintenance scheme is convention, not validated safety.
- Product quality is a major variable. Unregulated supply means contents, dose, purity and sterility vary, and contaminated or mis-dosed product is implicated in some of the serious case reports. Watch your skin, and do not treat “lots of people use it” as evidence of safety.
Research use only. Not medical advice. 18+.