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Melanotan II (MT-2) is a synthetic peptide analogue of a natural hormone involved in skin pigmentation, sexual function, and energy regulation. It was developed as a research tool to explore the melanocortin system and has been studied in early-phase human trials, though it has never been approved for medical use. All commercial and informal supply of MT-2 exists entirely outside regulated pharmaceutical channels.
What is Melanotan II
Melanotan II is a cyclic, seven-amino-acid peptide that mimics alpha-melanocyte-stimulating hormone (alpha-MSH), a signaling molecule produced naturally in the pituitary gland from the precursor protein pro-opiomelanocortin (POMC). It was synthesized in the late 1980s and 1990s at the University of Arizona as part of a tanning agent development program. The goal was to reduce skin cancer risk by inducing melanin production without requiring heavy UV exposure.
MT-2 is not a vitamin, supplement, or approved pharmaceutical. It is an investigational peptide that is not authorized for human use by any major regulatory agency, including the FDA, EMA, or TGA. Products sold as "Melanotan II" in online or gray markets have not been reviewed for safety, purity, or accurate dosing.
How it works
MT-2 is a non-selective agonist of the melanocortin receptor family. It binds to multiple receptor subtypes with different downstream effects:
| Receptor | Primary location | Associated effects |
|---|---|---|
| MC1R | Skin melanocytes | Melanin synthesis, skin darkening |
| MC3R | Hypothalamus, adipose tissue | Energy balance, appetite modulation |
| MC4R | Hypothalamus, spinal cord | Sexual arousal, erectile function, appetite suppression |
| MC5R | Exocrine glands | Sebaceous and sweat gland activity |
The broad receptor binding profile is what drives MT-2's range of reported effects, and also what underlies its side effect profile. Unlike a selective drug designed to hit one target cleanly, MT-2 activates several systems simultaneously. This lack of selectivity distinguishes it from later compounds derived from similar research, including bremelanotide (PT-141), which was engineered to be more selective for MC3R and MC4R and ultimately received FDA approval in 2019 for a specific indication (hypoactive sexual desire disorder in premenopausal women under the brand name Vyleesi).
What the research says
The most substantive human data on MT-2 comes from a series of small clinical trials conducted at the University of Arizona in the 1990s and early 2000s. These trials reported:
- Skin tanning: Subcutaneous MT-2 produced dose-dependent increases in skin pigmentation in fair-skinned participants, with significant darkening observed even with minimal UV exposure compared to placebo controls.
- Sexual function: Separate trials in men with psychogenic erectile dysfunction reported that MT-2 produced spontaneous erections at doses as low as 0.025 mg/kg, a finding that redirected some of the research toward sexual medicine.
- Appetite effects: Participants in tanning trials sometimes reported reduced appetite, consistent with MC4R activation in hypothalamic circuits that regulate feeding behavior.
These findings were notable enough to prompt further drug development. However, the development trajectory split: the tanning indication was not pursued commercially to approval stage, while the sexual function work eventually led (through a different compound) to the approved drug Vyleesi. MT-2 itself has no approved medical use.
Independent case reports and post-market surveillance have flagged concerns about mole changes and potential melanoma risk associated with informal MT-2 use, particularly when combined with UV tanning sessions. Regulatory agencies in several countries have issued public warnings specifically about these risks. The evidence is not sufficient to establish a definitive causal link, but the concern is taken seriously in the dermatology literature.
For context on how MT-2 compares to peptides in adjacent research areas, the best peptides for fat loss guide covers melanocortin system compounds alongside GLP-1 class agents.
Typical dosing
There is no standardized, clinically validated dosing protocol for MT-2 in humans. The numbers below are ranges reported in published research and informal protocols, provided as reference information only, not as dosing instructions.
| Context | Reported route | Reported dose range | Notes |
|---|---|---|---|
| Skin tanning (research) | Subcutaneous | 0.025 mg/kg to 0.1 mg/kg per dose | Once daily or several times per week |
| Erectile function (research) | Subcutaneous | 0.025 mg/kg (approx. 1.75 mg for 70 kg) | Single dose in trial settings |
| Informal protocols (community-reported) | Subcutaneous | 0.1-0.5 mg per dose | Variable; not from clinical studies |
The very wide range reflects the absence of agreed clinical guidance. Community protocols often describe a "loading phase" with daily low doses followed by "maintenance" doses, but this framing is not drawn from peer-reviewed research and has not been evaluated for safety.
Reconstitution math matters here: MT-2 typically comes as a lyophilized powder and requires mixing with bacteriostatic water before injection. The reconstitution guide walks through the concentration calculations. Subcutaneous injection technique, including site rotation to avoid lipodystrophy, is covered in the injection site rotation guide.
Anyone considering use of MT-2 should understand that the unregulated supply chain means product concentration, purity, and sterility cannot be assumed.
Side effects and safety
The side effect profile of MT-2 is well established from clinical trials and consistent with its broad melanocortin receptor activity:
Common (reported in clinical trials and informal use):
- Nausea and facial flushing, often appearing within 30-60 minutes of injection
- Fatigue or tiredness in the hours following a dose
- Spontaneous erections in males (considered an adverse event in tanning trials, a desired effect in sexual function trials)
- Yawning, stretching, and increased libido
- Darkening of existing moles or appearance of new pigmented lesions
Serious concerns:
- Case reports describe development of atypical nevi and melanoma in individuals using MT-2 with UV exposure, though causality has not been proven
- The FDA has warned that unregulated MT-2 products may be contaminated or mislabeled, creating additional safety risks beyond the compound itself
- No long-term human safety data exists; chronic effects on the cardiovascular system, hormonal axes, or skin biology are unknown
The nausea effect is strongly dose-dependent and was one of the primary reasons the tanning development program faced challenges. Some informal protocols describe using antiemetic medications alongside MT-2, which carries its own risks and is not medically endorsed.
MT-2 is on the WADA prohibited list and is therefore off-limits for any athlete subject to drug testing. It is also not available as a legally compounded medication in the United States.
Tracking Melanotan II with Redose
If you are using MT-2 in a supervised research or clinical context, Redose takes the friction out of protocol management. Log each injection with a single tap, track exactly how much peptide remains in each vial, rotate subcutaneous injection sites automatically so no area gets over-used, and let the app send discreet reminders when your next dose is due. The free reconstitution calculator at /calculators handles the concentration math for any combination of powder mass and BAC water volume. Download Redose at /#download for iPhone and Android.
This profile is educational information, not medical advice. Talk to a qualified healthcare provider before starting any protocol.