Melanotan II (MT-II)
Melanotan II: What The Studies Actually Say
It was made to tan skin. The tan was tested in people once, on 3 men. The other trials involved 20 men with erection problems, each watched for a few hours at a time. It is not approved anywhere we checked, and the serious harms on record come from case reports. Here is what the research actually found.
Updated 22 September 2026
Before you read this
This page explains what published studies found. That is all it is. It is not medical advice, and it is not instructions for using anything. Nothing here is meant to find, treat, cure or stop any illness. The compounds discussed on this site, retatrutide included, are not approved by the FDA for use in people. Research compounds are sold for laboratory use only — not for use in humans or animals. A study tells you what happened to the people in it. It does not tell you what would happen to you. What you do with what you read here is your responsibility, so talk to a doctor first. This page is published by Ascend Vials, which sells research compounds.
Read the full guide
Confirm you have read the notice above and enter an email address. We will send you a link back to this guide, and sometimes an email when we publish a new one. You can unsubscribe any time.
You may know it as the tanning jab, or the Barbie drug. It was built to darken skin. In its very first test in people, the volunteers also got erections.
Here is what the research actually found. Every claim has a link. Read them yourself.
The 30-second version
- Melanotan II is a lab-made copy of the body's own signal for skin pigment. It was first tested as a tanning drug that needs no sun.
- The tan was tested in people once, on 3 men. Two of them got darker.
- It also caused erections. In two small placebo-controlled trials of 10 men each, most men with erection problems got one after the shot.
- The fat-loss results come from rats and mice. We found no human weight-loss data.
- The serious harms on record, from melanomas to a 30-hour erection that needed surgery, come from case reports. They cannot say how often it happens or prove the drug did it.
- It is not approved anywhere we checked. Two approved drugs with similar names are different molecules.
- Nothing sold online has been shown to match what the studies used. No study has checked. When labs tested online products against their own labels, the amounts were off.
What it is
Melanotan II, or MT-II, is a lab-made peptide shaped like a ring. It is a shortened, sturdier copy of alpha-MSH, the hormone that tells skin to make pigment. Researchers at the University of Arizona designed it. ACS Pharmacol Transl Sci, 2024
In the 1990s they tested it in people as a way to tan without sun. It also caused erections, so they went on to test it for erectile dysfunction. Life Sci, 1996 · Int J Impot Res, 2000
Today people buy it illegally online for tanning, as nasal sprays and injections. TGA, 2025 It is also used as a sexual stimulant. Clin Toxicol, 2012 Medical journals have called it the "Barbie drug" and the "tanning jab." J Forensic Sci, 2024 · Ir Med J, 2013
The tan: one study, three men
The first human test was a pilot study in 3 healthy men. For two weeks their shots switched between MT-II and salt water, and they were not told which was which. Two of the 3 men got darker on the face, upper body and buttocks, measured one week after the last shot. Life Sci, 1996
They also had erections that came and went for 1 to 5 hours after a shot, with bouts of stretching and yawning. Mild nausea showed up at most dose levels. At the highest dose, 1 of 2 men had moderate sleepiness and tiredness. Life Sci, 1996
Three people cannot tell anyone whether a drug is safe or whether it works. That is all the human tanning data we found. A 2024 review says plans to sell MT-II for tanning were shelved because it switches on so much else in the body. ACS Pharmacol Transl Sci, 2024
And the tan is not sunscreen. No human study has shown it protects skin. Australia's drug regulator says a melanotan tan "will not protect against UV exposure the way a suitable sunscreen will." TGA, 2025
The erection trials
Next the team tested MT-II in men with erectile dysfunction. Apart from the pilot, these are the only controlled human trials we found. Each had 10 men. Each man got MT-II on some visits and a dummy shot on others, and neither he nor the researchers knew which. A monitor measured erections for 6 hours. J Urol, 1998 · Urology, 2000
The first trial tested men whose problem had no known physical cause. On MT-II, 8 of 10 got a clearly visible erection. J Urol, 1998
"Firm" means the tip was more than 80% rigid. The gap was statistically significant. J Urol, 1998
The second trial tested men with physical risk factors. They reported an erection after 12 of 19 MT-II shots, against 1 of 21 dummy shots. Firm time averaged 45.3 minutes on MT-II and 1.9 on the dummy. Sexual desire was higher after MT-II. Urology, 2000
Across both groups, the team reported that 17 of 20 men got an erection with no sexual stimulation. Int J Impot Res, 2000
The fine print: that is 20 men in total, each watched a few hours at a time. Nobody was followed for months. The scientists who designed the molecule co-wrote the 2000 papers. And we found no placebo-controlled MT-II trial in women. Urology, 2000
Three drugs people mix up
Two approved drugs are often confused with MT-II. They are not the same thing.
| Melanotan II | Bremelanotide (Vyleesi) | Afamelanotide (Scenesse) | |
|---|---|---|---|
| Shape | Ring | Same ring, one end different | Straight chain, 13 amino acids |
| Also called | MT-II, MT2 | — | Once called "melanotan I" |
| Approved | No, nowhere we checked | Yes: US, 2019 | Yes: EU 2014, US 2019 |
| Approved for | Nothing | Low sexual desire in women before menopause | A disease called EPP |
| Its results count for MT-II? | — | No | No |
Bremelanotide has MT-II's ring, but one end is an acid where MT-II's is an amide. A 2024 review calls it a breakdown product of MT-II. FDA's 2019 approval does not cover MT-II. Vyleesi label · FDA approval letter · ACS Pharmacol Transl Sci, 2024
Afamelanotide is a different molecule: a straight chain, not a ring. It is approved for erythropoietic protoporphyria (EPP). EMA · FDA
Read that last row again. The evidence and approvals for these two drugs do not transfer to Melanotan II.
How it is supposed to work
Your body has a family of switches called melanocortin receptors. In lab tests, MT-II turns on at least four of them at tiny amounts, and it does not favor one. ACS Pharmacol Transl Sci, 2024
One, MC1R, sits on pigment cells and makes them produce more melanin. That is the tan. Vyleesi label Others sit in the brain, gut and nerves. Peters, 2020 Those play a part in sexual arousal and erections, and in appetite and energy use. Mallory, 2021 · ACS Pharmacol Transl Sci, 2024
That fits what the trials saw: erections, yawning and stretching, nausea and less appetite. J Urol, 1998 In rats, it set off erections through the brain and the nerves outside it. Injected straight into the penis, it added nothing. Neuroscience, 2006
The fat-loss results are from rats
Any claim that MT-II burns fat comes from animals. We found no human weight-loss data.
- Obese mice lost weight and fat on MT-II. Mice fed the same amount without the drug lost as much weight but kept more fat. J Pharmacol Exp Ther, 2007
- The catch: rats learned to avoid a flavor paired with MT-II, the way they avoid one paired with a chemical that makes them sick. The authors say eating less on MT-II comes with unpleasant effects. Int J Obes, 2003
- Rats given MT-II into the brain for 10 days had blood pressure 9 points higher and hearts beating 27 times a minute faster. Hypertension, 2011
We found no controlled human trial of MT-II that reported blood pressure. A rat result is a reason to run a human study. It is not a human result.
Side effects in the trials
Nausea, stretching, yawning and less appetite were more common after MT-II than after the dummy shot. J Urol, 1998 In the second trial, 4 of 19 MT-II shots were followed by severe nausea. Urology, 2000 Looking back, the team put severe nausea at 12.9% of the men. Int J Impot Res, 2000 The researchers called the side effects manageable. J Urol, 1998 That verdict rests on about 20 men, each watched for a few hours.
Australia's regulator lists headache, nausea, vomiting, loss of appetite and facial redness as the most common side effects of melanotan. It calls skin cancer "the most concerning one." TGA, 2025 FDA warns that compounded MT-II may set off an immune reaction. FDA, 2026
The serious harms come from case reports
A case report is one doctor writing up one patient. It shows that something happened. It cannot show how often, and it often cannot prove the drug caused it.
Moles. Doctors in Germany reported new moles, and old ones darkening, 24 hours after a single MT-II shot. Case report, 2014 In Ireland, a patient had several new irregular moles within a week of two "Melanotan" shots of unstated type. Ir Med J, 2013
Melanoma. A 2017 review counted four reports of melanoma growing from existing moles during or soon after melanotan use. It said conclusive evidence linking the two "is lacking." Review, 2017 In a 2026 report, a 49-year-old man had five early-stage melanomas found about 2 to 3 weeks after starting melanotan: MT-II first, then melanotan I. He was also using tanning beds and unregulated testosterone. The melanomas may have been there already, and the authors say they cannot prove the drug caused them. Case report, 2026 A 22-year-old woman who used an MT-II nasal spray developed a melanoma in the lining at the front of her upper jaw. One case cannot prove the spray caused it. Case report, 2025
An erection that would not stop. A 55-year-old man had a painful erection for 30 hours after one MT-II shot. Drugs and draining failed, and he needed surgery. Fifteen weeks later he had erection problems he did not have before. Mallory, 2021
Intensive care. A 39-year-old man injected MT-II bought online, confirmed by a lab. His heart raced to 146 beats a minute, his muscles broke down and his kidneys struggled. He spent 3 days in intensive care. He had also tested positive for opiates. Clin Toxicol, 2012
Kidney. After 6 months of MT-II, with no other substances found, a healthy 45-year-old man lost blood supply to about half of his right kidney, and had new high blood pressure. The authors call MT-II a possible cause. Peters, 2020
Brain. A 2013 medical letter is titled "Melanotan and the posterior reversible encephalopathy syndrome." That syndrome, PRES, involves brain swelling. We could not read the details. Ann Intern Med, 2013 FDA also lists PRES among the harms in published case reports. FDA, 2026
How often does any of this happen? Nobody knows. The UK regulator received 13 suspected side-effect reports for MT-II from 2011 to 2021. It says a report does not prove the drug caused the problem, and that under-reporting is "unknown and variable." MHRA, 2021
Is it approved?
No. Not anywhere we checked.
United States. MT-II is not an FDA-approved drug. FDA treated it as an "unapproved new drug" and sent a warning letter to a US online seller in 2007. The seller's owner later pleaded guilty to two counts of conspiracy. FDA notice
FDA's list of compounding ingredients that "may present significant safety risks" shows MT-II's nomination as withdrawn. FDA, 2026 Its May 2026 list of compounding categories leaves MT-II out entirely. FDA, 2026 Neither makes it approved, and FDA has published no final decision.
Australia. It is prescription-only, not approved as a tanning agent, and not on the national register of medicines. In May 2026 a person in New South Wales paid fines totaling $101,412 (Australian) for alleged illegal supply. TGA, 2026
UK. The regulator decides case by case whether an MT-II product is a medicine, and has been removing melanotan products from sale for over 10 years. MHRA, 2021
Europe. It is not on the list of medicines authorized across the EU. EMA
What is still unknown
- Long-term safety, at any amount. No trial has followed users for months.
- Whether it causes melanoma, or speeds it up. There are only case reports.
- Whether the tan protects skin from UV at all.
- How often harms happen in the people using it.
- What it does in women, or to the heart in people.
- Whether mole changes fully go away after stopping.
- Whether it has any medical use. A vitiligo trial in China is listed as recruiting. It has no results, and its registry entry oddly calls itself an "example." Trial record
What is in the bottle is not what was studied
One more thing.
Every trial result on this page came from a few small studies in the 1990s, run by the university group that designed the molecule.
No study has ever shown that a product sold online as "Melanotan II" is the same thing those studies used. Not the same purity. Not the same strength. Not even proof it is the same molecule.
When labs tested what is sold, the labels were wrong. Vials from three online shops, each sold as 10 mg, held 4.32 to 8.84 mg. Two shops' vials held unknown impurities. Vial test Australia's regulator tested 5 nasal sprays, all labeled "30 MG." They held an estimated 22 to 54 mg. TGA, 2026
So take every number on this page for what it is. It describes one research team's MT-II in 23 men, plus case reports. It describes nothing else.
How to check a number yourself
You are going to see more claims about Melanotan II. In a reel. In a comment. On somebody's store page.
Here is how to tell a real one from a marketing one. Five questions. About ten seconds each.
1. Is there a link to a study?
A real number comes from a paper you can open. No link means it is a claim, not a result. Search the name on pubmed.gov yourself. If nothing comes back, nothing was published.
2. How many people, and for how long?
Small studies swing. The tan result is 3 men over 2 weeks. The erection results are 20 men, watched a few hours at a time.
3. Was there a group that got nothing?
In the erection trials every man also got a dummy shot. That is why 38 minutes against 3 means something. Without that comparison, nobody can tell what came from the drug.
4. Is it the same molecule?
Bremelanotide, afamelanotide, melanotan I and "melanotan" of unknown type are not MT-II. Their results are not MT-II results.
5. Is it a trial, a case report, or a rat?
A case report shows something happened to one person. A rat result is a reason to test people. Only a trial with a comparison group can start to tell you how often, and whether the drug did it.
Now run those five on this page
Every number above links to its paper. The study sizes are in the text. The dummy-shot result is in the chart. The case reports and rat studies are labeled as such.
Whatever a seller claims MT-II does for fat, sun protection or women, there is no human trial to link to, because we found none.
That is the whole difference: a number you can check, and a number you are asked to believe.
This page has a date on it, near the top. If a real trial of MT-II is ever published, this page changes.
Read the studies yourself
- Human trials: Dorr, Life Sci 1996 — the tan pilot · Wessells, J Urol 1998 · Wessells, Urology 2000 · Wessells, Int J Impot Res 2000
- Nicknames: J Forensic Sci 2024
- How it works: Weirath & Haskell-Luevano, ACS Pharmacol Transl Sci 2024 — free to read · Giuliano, Neuroscience 2006
- Rats and mice: Strader 2007 · Benoit 2003 · do Carmo 2011
- Case reports: Germany 2014 · Ir Med J 2013 · Review 2017 · Case report 2026 · UK 2025 · Mallory 2021 · Nelson, Clin Toxicol 2012 · Peters 2020 · Ann Intern Med 2013
- What is in the bottle: Vial test · TGA spray test, 2026
- Rules: FDA safety-risk list · FDA compounding categories · FDA notice · TGA, 2025 · MHRA, 2021 · EMA medicines list · Vitiligo trial record
- The approved look-alikes: Vyleesi label · Vyleesi approval letter · Scenesse, EMA · Scenesse, FDA
The amounts above describe what labs and regulators found in products for sale, not what anyone should take. This is not advice, a plan, or instructions. Melanotan II is not an approved medicine. Research compounds are not for human or animal use.