MT-2What the studies show

Q: What kind of evidence exists for melanotan II?

Small human studies. A few small, short human studies from one university in the 1990s, plus case reports from unregulated use; no controlled trial of any length and no approved form.

A seven-amino-acid ring that tanned a handful of men in the 1990s, gave them unplanned erections, and was never approved anywhere.

5 min read · Small human studies · Updated November 2026

In short

Name: melanotan II (sold by Progression Labs as MT-2)
Evidence: Small human studies
Bottom line: A few small, short human studies from one university in the 1990s, plus case reports from unregulated use; no controlled trial of any length and no approved form.

Before you read this

This guide explains what published studies found. That is all it is.

It is not medical advice and it is not instructions for using anything. Where a dose appears, we are reporting what a named study gave the people or animals in it — a fact about the study, not an instruction to you.

The compounds here are not approved by the FDA for use in people and are sold for laboratory research only. A study tells you what happened to the subjects in it; it does not tell you what would happen to you. Talk to a doctor first.

What it is

Melanotan II is a ring of seven amino acids, made at the University of Arizona in the late 1980s as a shorter and more stable version of alpha-melanocyte-stimulating hormone, the hormone that tells pigment cells to make melanin ¹. Its sibling melanotan I is a straight 13-amino-acid chain that acts mostly on the pigment receptor in skin. Melanotan II is cyclic, reaches the brain, and binds several melanocortin receptors at once, including the ones that govern appetite and sexual arousal; that spread of targets is why it tans and also why it does other things ¹. It has never been approved as a drug anywhere. Its lasting contribution to medicine is a metabolite, bremelanotide, which was developed separately and became the approved drug Vyleesi ¹.

The studies below call this molecule melanotan II. Progression Labs sells it as MT-2; the guide uses the store's name and the papers use theirs.

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Tanning: the 1996 pilot

The first report in people was a pilot study published in 1996: a small group of healthy men received melanotan II under the skin over several days, their skin darkened without sun exposure, and the investigators recorded nausea, stretching and yawning as side effects — along with spontaneous erections, which no one had set out to study ². The study was designed to see whether the peptide could produce a protective tan in people at high risk of skin cancer; it never went further than early trials for that purpose ¹.

Erections: the 1998 crossover

The side effect became the subject. In 1998, ten men with psychogenic erectile dysfunction — no physical cause found — were given melanotan II or placebo under the skin on separate days in a double-blind crossover; erections were recorded in eight of the ten after the peptide, without sexual stimulation, and nausea and yawning were again the main side effects ³. The same group then saw a response in men whose erectile dysfunction had a physical cause ¹. Those results were carried forward with the metabolite bremelanotide, which kept the sexual effect and lost most of the tanning, rather than with melanotan II itself ¹.

Moles, melanoma reports and unregulated products

Melanotan II stalled as a drug but, from the mid-2000s, was sold on the internet as a tanning injection. A 2009 report in the BMJ described patients whose existing moles darkened and new moles appeared after they used products bought online ⁴. Dermatologists have since published case reports of rapidly changing moles and of melanoma diagnosed in users; a 2017 review in the International Journal of Dermatology collected them and concluded that a causal link to melanoma is unproven but biologically plausible, since the peptide stimulates the same cells melanoma comes from ⁵.

The same review notes that the products are unregulated — content, dose and purity unverified — and that drug regulators in several countries, including the United States and the United Kingdom, have issued public warnings against injectable melanotan sold for tanning ⁵. Other effects reported in users and in the trials include nausea, flushing, loss of appetite and prolonged erections ⁵.

What is not known

No placebo-controlled trial of melanotan II has run longer than a few weeks or in more than a few dozen people, so there is no data on what months or years of exposure do to pigment cells or anything else. The receptors it hits include the one that regulates appetite and energy balance, and none of that was measured in the 1990s studies. It is not an approved drug anywhere, every product sold under the name sits outside any regulator's oversight, and the melanocortin peptide that did get long trials is its metabolite, not melanotan II ⁵.

What these studies are, and aren't

Small human studies. A few small, short human studies from one university in the 1990s, plus case reports from unregulated use; no controlled trial of any length and no approved form.