What is Melanotan II? What it does, benefits and what the evidence shows

Melanotan II (MT-II) is a synthetic, ring-shaped peptide modeled on alpha-melanocyte-stimulating hormone, the signal that tells skin cells to make pigment. In small studies published between 1996 and 2000 it darkened skin and caused spontaneous erections and nausea. It has never been approved as a medicine anywhere we could find, there is no large trial of it, and published case reports link unregulated use to changes in moles, melanoma, prolonged painful erections (priapism) and kidney and muscle injury. Most of what is sold online as a tanning shortcut rests on a handful of tiny early studies and a lot of forum experience.

What Melanotan II is and how it works

Melanotan II is a cyclic heptapeptide, meaning seven amino acids joined into a ring. In the first human report it was described as a lactam-bridged analogue of a fragment of alpha-MSH (residues 4 to 10), with a chemical structure that ends in an amide group (Dorr et al., Life Sciences, 1996). It is not selective: it switches on several melanocortin receptors at once, which is why it does more than tan. Activating the skin receptor (MC1R) drives pigment; activating melanocortin receptors in the brain is thought to underlie the erections, and the effect on sexual desire was reported in men (King et al., Current Topics in Medicinal Chemistry, 2007; Wessells et al., International Journal of Impotence Research, 2000).

It is the parent of two better-known relatives. Bremelanotide (PT-141) is described in a 2007 review as the carboxylate derivative of MT-II (King et al., Current Topics in Medicinal Chemistry, 2007); the FDA label for the approved product Vyleesi shows the same ring with a free acid end instead of an amide (Vyleesi label, DailyMed). We cover that one in our PT-141 guide. Melanotan I is a longer, straight-chain analogue that acts mainly on the skin receptor; its story is in the Melanotan I guide. MT-II is the one with the sexual effects, and also the one with the most reported problems.

What people use it for

What the research actually shows

Tanning

The first human study was a pilot in three healthy men, single-blind and placebo-controlled, run for two weeks. Two of the three had visibly and measurably more pigment in the face, upper body and buttocks a week after the last injection, and the authors concluded MT-II has tanning activity in people. Nausea was reported at most dose levels, one participant had significant sleepiness and fatigue at the highest dose reached, and a stretching and yawning pattern showed up alongside spontaneous erections lasting hours (Dorr et al., Life Sciences, 1996).

Three people is a pilot, not proof of how well it works or how safe it is. We did not find a larger controlled tanning trial of MT-II. What the trial does show is that the tan is real but comes bundled with effects you cannot switch off.

Erections and sexual desire

The stronger signal is sexual. In a double-blind, placebo-controlled crossover study of ten men with psychogenic erectile dysfunction, eight developed clinically apparent erections after MT-II, with far longer periods of firm erection than on placebo; nausea, stretching and yawning, and decreased appetite were reported more often on MT-II (Wessells et al., Journal of Urology, 1998). A follow-up review of 20 men with psychogenic and organic erectile dysfunction reported erections without sexual stimulation in 17 of 20, increased desire after 13 of 19 MT-II doses versus 4 of 21 placebo doses, and severe nausea in 12.9% of participants at the dose they tested (Wessells et al., International Journal of Impotence Research, 2000).

These are small, short, single-group-of-volunteers studies from a quarter century ago. They show the effect exists. They do not show MT-II is a safe or reasonable erectile drug. The melanocortin drug that later reached approval for a sexual indication was bremelanotide, not MT-II.

Appetite, fat loss and "sun protection"

Reduced appetite appears in the 1998 study as a transient side effect, not as a weight-loss result. We found no trial of MT-II for fat loss. We also found no study showing that an MT-II tan protects against sunburn or skin cancer. A darker skin is not the same as safer skin, and the reports below concern exactly that.

Side effects and risks

MT-II was never through the trials that produce a label, so there is no official list of expected side effects and no incidence figures. What exists is trial observations, published case reports and analyses of products, and you should read it as a signal, not a statistic.

What the trials saw

Nausea, stretching and yawning, sleepiness and fatigue, decreased appetite and spontaneous erections were all reported in the early studies above. In the 20-man review, severe nausea affected 12.9% of participants at the tested dose (Wessells et al., 2000).

Moles and melanoma

Several case reports describe new or changed moles after melanotan injections, including some that name MT-II. A patient developed multiple new atypical moles within a week of two melanotan injections (the abstract does not say which melanotan) (Reid et al., Irish Medical Journal, 2013), and another report describes eruptive new moles and darkening of existing ones within 24 hours of a single injection (Schulze et al., European Journal of Dermatology, 2014). A 20-year-old woman with fair skin was diagnosed with melanoma after a three-to-four-week course of MT-II used together with sunbed tanning, with the lesion excised about three months after that course; the authors say the combination coincided with the melanoma and stress that the drug is unlicensed and incompletely tested (Hjuler and Lorentzen, Dermatology, 2014). A 2025 report describes a mucosal melanoma in the mouth of a 22-year-old woman who had used an MT-II nasal spray for tanning (Yassin Alsabbagh et al., International Journal of Oral and Maxillofacial Surgery, 2025).

The honest reading: a 2017 dermatology review counted four case reports of melanomas emerging from existing moles during or shortly after melanotan use and said conclusive evidence linking the two is lacking, while noting that multiple national health organizations have issued safety warnings (Habbema et al., International Journal of Dermatology, 2017). Case reports cannot prove cause. Several of the reports also involve sunbed use, which muddies the picture. Still, the drug's whole purpose is to push pigment cells to darken, so the signal is one to take seriously, especially if you have many moles, a history of melanoma or fair skin.

Priapism

Prolonged, painful erections have been reported. One patient presented with low-flow priapism after a melanotan injection (the abstract doesn't say which melanotan), needed drainage and an injected drug to treat it, and had not regained erectile function at four weeks (Dreyer et al., BMJ Case Reports, 2019). Another needed surgical decompression after ischemic priapism from MT-II, and the authors noted that priapism after MT-II had only been reported twice before (Mallory et al., Sexual Medicine, 2021). The authors of the earlier BMJ Case Reports paper are the ones who call priapism a potentially life-altering complication.

Muscle, kidney and other reports

A man developed a fast heart rate, anxiety, tremors, muscle breakdown (rhabdomyolysis) and kidney injury after an MT-II injection, and the substance he used was confirmed by mass spectrometry to be MT-II (Nelson et al., Clinical Toxicology, 2012). A 2020 report and literature review discussed a renal infarction most likely attributed to MT-II (Peters et al., CEN Case Reports, 2020). An analysis of UK and Irish online forum discussions flagged infectious disease transmission, potentially contaminated products, polypharmacy and sunbed use alongside the skin-lesion concern (Gilhooley et al., Dermatology, 2021).

Regulators

An FDA notice of opportunity for hearing is a 2016 proposal to debar an individual seller after a federal conviction, and it recounts a warning letter FDA sent his company on August 30, 2007, saying MT-II was a new drug that could not be introduced into interstate commerce without an approved application and that selling it without one violated federal law (FDA notice of opportunity for hearing). It is a proceeding against a person, not a safety review of the peptide. FDA's page on bulk substances flagged for compounding safety concerns also lists Melanotan II among those "nominated but withdrawn," noting a possible immunogenicity risk and published case reports of serious adverse events including melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome and priapism (FDA, content current as of 04/22/2026).

What's in the vial

Independent analysis of injectable MT-II bought from three online shops found impurities of about 4% to 6% in vials from two of them, and total peptide content between 4.32 and 8.84 milligrams where each shop claimed 10 (Breindahl et al., Drug Testing and Analysis, 2015). Police-seized samples sold alongside anabolic steroids and other bodybuilding drugs included both MT-II and bremelanotide (Mestria et al., Drug Testing and Analysis, 2021). Two datasets are not a market survey, but they tell you that the label is not a guarantee.

What the lab tests show

As of September 29, 2026, VendorVerify's database has one Melanotan II vial, from April 2026: 99.93% pure and about 13% over its labelled amount. That vial did not meet our failure definition (empty, under 95% pure, more than 20% under label or more than 50% over). One vial says almost nothing about the market and nothing about any vendor, and purity and amount say nothing about sterility, about endotoxin, or about the safety concerns above. If you have had an MT-II vial tested, submitting the report adds to a dataset that is currently one data point. Compound-level results are on the Melanotan II results page.

Because we don't have enough lab data on this compound to rank vendors for it, here are the highest-ranked vendors across all compounds right now. A vendor's overall record is a signal, not a guarantee for a compound they have never had tested.

Buying smarter

With one vial in the database, general checks matter more than any compound-specific ranking. Look at each vendor's full record and how many reports sit behind the score. Treat a vendor-posted COA as a starting point (how to read a peptide COA, fake peptide COAs). Because an unlicensed injectable is the higher-risk category, paying for identity, purity and quantity testing on your own vial is worth considering, and endotoxin testing is worth adding; how to get a peptide tested walks through it. The quantity gap between labels and contents is covered in underdosed peptides.

If a report comes back with a fail, stop using that batch, tell anyone who bought from the same run, bring the report to the vendor, and submit it to VendorVerify. Related reading: the approved sibling PT-141, the Melanotan I guide, and the peptide hub.

Database figures are from VendorVerify as of September 29, 2026. This isn't medical advice; Melanotan II is unapproved, sold for research use only, and the safety information above comes from case reports and small early studies.