Melanotan II
A tanning and libido injection that was never approved: small 1990s trials, rodent data and a trail of case reports
Melanotan II is a cyclic, seven-amino-acid version of the hormone α-MSH that switches on melanocortin receptors across the body. In small 1990s trials it darkened the skin of two of three volunteers after five doses and caused erections in most men who took it, with frequent nausea. It was never approved. Sold now as an unregulated tanning injection, it comes with case reports of melanoma, priapism and kidney injury, and with vials that tested short of their label.
What is it?
Melanotan II is a shortened, ring-shaped copy of α-melanocyte-stimulating hormone: residues 4 to 10 of the natural hormone, with norleucine swapped in and a lactam bridge closing the ring. The changes make it far more potent than the hormone at melanocortin receptors, and it acts on several of them, including MC1R in pigment cells and MC3R and MC4R, which are tied to appetite and sexual function. That lack of selectivity explains both why people take it and most of what goes wrong.
The human data are small and old. In a 1996 pilot, three healthy men took it on alternate days for two weeks; two tanned visibly on the face, upper body and buttocks, and the men had spontaneous erections that came and went for one to five hours after doses, along with yawning and stretching. In erectile-dysfunction trials, 8 of 10 men with psychogenic dysfunction developed erections, and across 20 men, 17 had erections without sexual stimulation. Nausea was the price: severe after 12.9% of doses at the standard 0.025 mg/kg.
It was never approved, though two relatives were. Afamelanotide, once called melanotan I, is approved as Scenesse for a rare light-sensitivity disorder; bremelanotide (PT-141), which differs from melanotan II only at its tail end, is approved as Vyleesi for low sexual desire in premenopausal women. Melanotan II itself is sold as an unregulated injection, mostly for tanning. Users on UK and Irish forums described taking it before holidays and bodybuilding shows, often alongside sunbeds, and vials bought from three online shops held 4.32 to 8.84 mg of drug against 10 mg on the label.
The safety record is case reports and warnings rather than trials. A 2017 review counted four reports of melanoma emerging from existing moles during or shortly after melanotan use, alongside changing moles and new atypical ones, while stressing that conclusive evidence is lacking. Other reports describe priapism after an overdose and a renal infarction attributed to melanotan II. In the US its nomination left FDA's Category 2 in April 2026 only because it was withdrawn, and it waits on an advisory-committee review slated before the end of February 2027.
Mechanism of Action
Melanotan II binds all the human melanocortin receptors it has been tested against, which is why one injection can tan the skin, trigger an erection and blunt appetite at the same time. The pathways below come from human trials for the first two and from rodents for the rest.
Tanning and erections were seen in a handful of men in the 1990s; the appetite effects come from rodents. It was never developed into an approved product, and what is sold online is untested.
Each step is tagged with where it was shown. A dashed red arrow marks a link the evidence does not establish.
The pathway in words
- Melanotan II. A cyclic analogue of alpha-MSH and a potent but unselective agonist of human melanocortin receptors. Shown in: lab. Source: PubMed 35188390.
- Darker skin. In a pilot in three healthy men, two developed increased pigmentation of the face, upper body and buttocks, still measurable a week after the last dose. Shown in: people. Source: PubMed 8637402.
- Erections and desire. In crossover trials in 20 men with erectile dysfunction, 17 had erections without stimulation, and desire rose after 68% of doses against 19% of placebo. Shown in: people. Source: PubMed 11035391.
- Appetite and fat. In rats, a brain infusion stopped eating for one to two days and halved fat against pair-fed rats; obese mice lost more fat than eating less explained. Shown in: animals. Source: PubMed 12535159, 17567964.
- never tested; harms reported. Safe as a tanning product. Online vials labelled 10 mg held 4.3 to 8.8 mg with impurities, and case reports describe kidney infarction; no trial has tested this use. Shown in: review. Source: PubMed 24771717, 31953620.
MC1R: pigment
Melanocortin-1 receptors on pigment cells drive melanin production. Two of three men in the 1996 pilot tanned after five low doses, confirmed by reflectance measurements a week after dosing ended. Dermatologists writing about users flag moles for the same reason: the drug acts on melanocytes wherever they are.
Erection and desire
Melanocortin signalling produced erections without sexual stimulation in most men tested, with a yawning-and-stretching complex, and raised reported desire after 68% of doses against 19% on placebo. In conscious rats, 1 mg/kg intravenously raised erectile activity measured by telemetry.
Appetite and fat
A week-long brain infusion stopped rats eating for a day or two before intake returned to normal despite continued dosing, halved fat compared with pair-fed rats and cancelled the overeating driven by neuropeptide Y. Under the skin, it improved insulin sensitivity in diabetes-prone rats and cut fat in obese mice beyond what eating less explained.
Kidneys
A 2020 case report and review attributes a renal infarction to melanotan II and notes earlier reports of rhabdomyolysis and kidney failure. The authors raise a clotting effect and direct toxicity to kidney tissue as possible mechanisms; neither has been shown.
Published Research
Our evidence set returned 44 papers for melanotan II, but 17 are about other things abbreviated MT2: melatonin receptors, metallothionein and an HIV cell line. Of the rest, 16 name melanotan II in their titles, and 14 are carded below: two human studies, a forum study of users, a vial analysis, a case report with review, rodent pharmacology and receptor chemistry. Five more appear in References without a card: the two original erectile-dysfunction trials and a risk review, which PubMed indexes under melanotan-II but whose titles do not name it, and two letters with no abstract, on priapism after an overdose and on melanoma.
Phase I pilot: tanning and erections
Three healthy men took subcutaneous melanotan II on alternate days for two weeks, from 0.01 mg/kg up to 0.025–0.03 mg/kg. Two developed increased pigmentation of the face, upper body and buttocks, still measurable a week after the last dose. Spontaneous erections came and went for one to five hours after doses, with yawning and stretching; mild nausea occurred at most doses, and 0.03 mg/kg caused grade II sleepiness and fatigue in one of two men.
Erections and desire in 20 men with ED
Summarising crossover trials in 20 men with psychogenic or organic erectile dysfunction, the authors report erections without sexual stimulation in 17 of 20, a mean of 41 minutes of strong tip rigidity, and more desire after 13 of 19 melanotan doses (68%) than after 4 of 21 placebo doses (19%, p < 0.01). Nausea and yawning were common, and at 0.025 mg/kg 12.9% had severe nausea.
What users say on forums
Researchers analysed 623 posts from 205 people on UK and Irish forums between January 2016 and October 2017. Users took melanotan II to tan before holidays and fitness or bodybuilding competitions, traded misinformation about an unregulated product, and often combined it with sunbeds. The authors flag pigmented skin lesions, infection from injecting, contaminated products and polypharmacy as risks clinicians should know.
What was actually in the vials
Vials sold by three online shops as 10 mg melanotan II injections contained between 4.32 and 8.84 mg of the drug. Vials from two of the shops carried unknown impurities of 4.1% to 5.9%; the third shop's were below the quantification limit.
Renal infarction: case report and review
The authors describe a renal infarction they consider most likely caused by melanotan II and review earlier reports of rhabdomyolysis and kidney failure with the drug. They propose a clotting-related effect and direct kidney toxicity as possible mechanisms, without establishing either.
Erections in rats, measured by telemetry
Pressure sensors implanted in rats' penile tissue showed that 1 mg/kg melanotan II given intravenously significantly raised erectile activity in freely moving animals. In anaesthetised rats the rise followed the same pattern but was not statistically significant.
Appetite, fat and neuropeptide Y
A week-long infusion into rats' brains (15 nmol a day) caused almost complete loss of appetite for one to two days, after which eating returned to normal despite continued infusion. Fat mass fell to half that of pair-fed rats, and melanotan II cancelled the overeating and fat gain driven by co-infused neuropeptide Y.
Insulin sensitivity in diabetes-prone rats
Given under the skin by osmotic pump, melanotan II cut food intake and body weight in OLETF rats, a model of type 2 diabetes. Treated rats were more insulin-sensitive than both freely fed and pair-fed rats, and had lower glucose on tolerance tests than freely fed rats.
Fat loss beyond eating less
Obese mice on a high-fat diet lost weight and body fat on melanotan II, while mice on a low-fat diet held their weight. Pair-fed obese mice lost as much weight but kept more fat, so the drug's effect on fat went beyond reduced eating. The result was repeated in rats.
Appetite without aversion in mice
Injected into the nucleus accumbens of mice at 0.1 to 1 nmol, melanotan II reduced food intake and the effort animals would make to earn food, without producing taste aversion or changing metabolic rate.
No protection from cisplatin hearing damage
In guinea pigs given the chemotherapy drug cisplatin, melanotan II at 3 or 30 µg/kg a day did not delay hearing damage or speed recovery, unlike other melanocortins the same group had tested.
Heat production in PACAP-deficient mice
Three weeks of daily melanotan II injections during cold exposure partly restored the impaired heat-producing capacity of female mice lacking the neuropeptide PACAP and corrected their fat-mobilisation deficit, which suggests PACAP acts upstream of melanocortin receptors.
Memory in zebrafish on a high-fat diet
Zebrafish fed a high-fat diet for three weeks showed impaired recognition memory, more anxiety and less exploration. Fish treated with melanotan II on the same diet behaved like fish on the control diet on all three measures.
A non-selective agonist, re-engineered
Describing melanotan II as a potent but unselective agonist of human melanocortin receptors, chemists replaced its lactam ring with xylene-based links. The new peptides bound the receptors at low-nanomolar to sub-micromolar affinity, and one was markedly selective for MC1R, the pigment receptor.
What people say, and what was measured
Melanotan II is unusual: what its users say has itself been studied. A 2021 analysis of online forums, read by dermatologists, records the motivations and practices of 205 users, so the claims below can be quoted from the literature rather than from anyone selling it.
A few injections give you a deep tan before a holiday or a competition.
Heard in: Dermatology, Melanotan II User Experience: A Qualitative Study of Online Discussion Forums, which found the pursuit of a tanned appearance, often before sun holidays and fitness or bodybuilding competitions, was the main motivation among 205 users (read October 1, 2026). Source
The tanning effect is real in people, though measured in very few. In a pilot study of three men given five low doses every other day, two had increased pigmentation of the face, upper body and buttocks a week after dosing ended, measured by reflectance. The study recommended 0.025 mg/kg as the dose for further trials, and nausea occurred at most dose levels. PMID: 8637402
Tested in people; supportedIt raises libido and causes erections.
Heard in: CEN Case Reports, Melanotan II: a possible cause of renal infarction, which describes its effects in people as increased skin pigmentation, spontaneous penile erection and sexual stimulation (read October 1, 2026). Source
This was measured in a controlled study. In 20 men with erectile dysfunction, melanotan II produced erections without sexual stimulation in 17, and increased sexual desire after 68% of doses against 19% of placebo doses. It is the observation that led to bremelanotide, the approved drug for low sexual desire. At 0.025 mg/kg, 12.9% of men had severe nausea. PMID: 11035391
Tested in people; supportedIt is safe; the only side effects are a bit of nausea and flushing.
Heard in: Dermatology, Melanotan II User Experience, which records misinformation in the context of using an unregulated product and concerning practices among forum users (read October 1, 2026). Source
The trials were tiny and short, and still found more than flushing: severe nausea in 12.9% of men at the effective dose, somnolence and fatigue, and stretching and yawning before erections. Beyond the trials, a 2020 case report attributes a kidney infarction most likely to melanotan II and reviews earlier reports of muscle breakdown and kidney failure. The forum study's authors warn about pigmented skin lesions, infections from shared equipment, contaminated products and sunbed use. PMID: 11035391, 8637402, 31953620, 34464955
Tested in people; not shownA 10 mg vial contains 10 mg of melanotan II.
Heard in: Grey Peptides listing review, October 1, 2026: melanotan II is sold online in vials labelled 10 mg. Sellers are not named.
When vials bought from online shops were analysed by liquid chromatography and mass spectrometry, each shop having claimed 10 mg a vial, the vials held between 4.32 and 8.84 mg. Vials from two shops also contained unknown impurities at 4.1 to 5.9%. PMID: 24771717
Tested in products; not trueEach claim is quoted from where it is said, never from a seller, and checked as of October 1, 2026 against the studies listed below.
Dosing Data
Melanotan II has no approved dose. The human doses on record are per-kilogram doses from trials in 23 men in the 1990s; the figures in circulation now are flat milligram doses with no trial behind them.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
→ Full Melanotan II dosage guide — the per-kilogram trial doses, the flat doses in circulation, and why the two are hard to compare.
→ Blend & Stack Calculator — Melanotan II is also sold in multi-peptide vials; the calculator shows what each draw delivers of every component; our blends and stacks hub sets out what each mix contains and what has been studied.
Side Effects & Contraindications
Reported Side Effects
These come from the small trials, the forum study and published case reports. A case report shows that something happened, not how often it happens.
Contraindications & Cautions
No trial defined who should avoid melanotan II. These cautions follow from the reports above and from how the drug is used.
Legal Status
Melanotan II is not approved as a medicine in any of the jurisdictions below, although its relatives afamelanotide and bremelanotide are. In the US it waits on FDA's compounding advisory committee, slated to review it by the end of February 2027. Status as of September 26, 2026.
Frequently Asked Questions
?Is melanotan II the same as afamelanotide or PT-141?
No, though all three come from α-MSH. Afamelanotide, once called melanotan I, is FDA-approved as Scenesse for phototoxic reactions in erythropoietic protoporphyria. Bremelanotide (PT-141) differs from melanotan II only at its tail end, a free acid where melanotan II has an amide, and is FDA-approved as Vyleesi for hypoactive sexual desire disorder in premenopausal women. Melanotan II itself is approved nowhere.
?Does melanotan II cause melanoma?
No study can say. By 2017 a review counted four case reports of melanoma emerging from existing moles during or shortly after melanotan use, alongside reports of changing and new atypical moles, and it stressed that conclusive evidence is lacking. The trials were far too small and short to measure cancer risk. The drug acts on moles as well as skin, so new or changing moles need a dermatologist.
?Why does melanotan II cause erections?
It activates melanocortin receptors involved in sexual function as well as pigment. In small trials it produced erections without sexual stimulation in 17 of 20 men with erectile dysfunction, and in healthy volunteers spontaneous erections came and went for up to five hours after a dose. The same effect lies behind the reports of priapism, an erection that will not subside.
?How much melanotan II is in a 10 mg vial?
Possibly much less. A 2015 analysis of vials from three online shops found 4.32 to 8.84 mg against 10 mg on the label, and vials from two of the shops carried 4.1% to 5.9% unknown impurities.
?Can a US pharmacy compound melanotan II?
No. Its nomination left Category 2 in April 2026 because it was withdrawn, and it was not placed in Category 1. FDA's compounding advisory committee is slated to review it by the end of February 2027, with no date set. Status as of September 26, 2026.
?Does melanotan II suppress appetite?
In rodents, at first: a brain infusion stopped rats eating for a day or two before intake returned to normal despite continued dosing, and treated animals lost fat. Men in the erectile-dysfunction trials reported reduced appetite more often than on placebo, but no human trial measured weight. Setmelanotide, which targets MC4R selectively, is the approved drug working through this pathway, for rare genetic forms of obesity.
References
- [pubmed] Dorr RT, et al. "Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study." Life Sci, 1996;58(20):1777-84. PMID: 8637402.
- [pubmed] Wessells H, et al. "Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II." Int J Impot Res, 2000;12 Suppl 4:S74-9. PMID: 11035391.
- [pubmed] Gilhooley E, et al. "Melanotan II User Experience: A Qualitative Study of Online Discussion Forums." Dermatology, 2021;237(6):995-999. PMID: 34464955.
- [pubmed] Breindahl T, et al. "Identification and characterization by LC-UV-MS/MS of melanotan II skin-tanning products sold illegally on the Internet." Drug Test Anal, 2015;7(2):164-72. PMID: 24771717.
- [review] Peters B, et al. "Melanotan II: a possible cause of renal infarction: review of the literature and case report." CEN Case Rep, 2020;9(2):159-161. PMID: 31953620.
- [pubmed] Giuliano F, et al. "The use of telemetry technology to test the proerectile effect of melanotan-II (MT-II) in conscious rats." Eur Urol, 2005;48(1):145-51; discussion 151-2. PMID: 15967265.
- [pubmed] Raposinho PD, et al. "The melanocortin agonist Melanotan-II reduces the orexigenic and adipogenic effects of neuropeptide Y (NPY) but does not affect the NPY-driven suppressive effects on the gonadotropic and somatotropic axes in the male rat." J Neuroendocrinol, 2003;15(2):173-81. PMID: 12535159.
- [pubmed] Banno R, et al. "The melanocortin agonist melanotan II increases insulin sensitivity in OLETF rats." Peptides, 2004;25(8):1279-86. PMID: 15350695.
- [pubmed] Strader AD, et al. "The effects of the melanocortin agonist (MT-II) on subcutaneous and visceral adipose tissue in rodents." J Pharmacol Exp Ther, 2007;322(3):1153-61. PMID: 17567964.
- [pubmed] Eliason NL, et al. "Melanocortin receptor agonist melanotan-II microinjected in the nucleus accumbens decreases appetitive and consumptive responding for food." Neuropeptides, 2022;96:102289. PMID: 36155088.
- [pubmed] Wolters FL, et al. "Co-treatment with melanotan-II, a potent melanocortin, does not protect against cisplatin ototoxicity." Hear Res, 2002;172(1-2):110-7. PMID: 12361873.
- [pubmed] McMillan TR, et al. "Melanotan II, a melanocortin agonist, partially rescues the impaired thermogenic capacity of pituitary adenylate cyclase-activating polypeptide deficient mice." Exp Physiol, 2021;106(2):427-437. PMID: 33332767.
- [pubmed] Wekwejt P, et al. "Melanotan-II reverses memory impairment induced by a short-term HF diet." Biomed Pharmacother, 2023;165:115129. PMID: 37478579.
- [pubmed] Tomassi S, et al. "CLIPSing Melanotan-II to Discover Multiple Functionally Selective hMCR Agonists." J Med Chem, 2022;65(5):4007-4017. PMID: 35188390.
- [pubmed] Wessells H, et al. "Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study." J Urol, 1998;160(2):389-93. PMID: 9679884.
- [pubmed] Wessells H, et al. "Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction." Urology, 2000;56(4):641-6. PMID: 11018622.
- [review] Habbema L, et al. "Risks of unregulated use of alpha-melanocyte-stimulating hormone analogues: a review." Int J Dermatol, 2017;56:975-980. PMID: 28266027.
- [pubmed] Paurobally D, et al. "Melanotan-associated melanoma." Br J Dermatol, 2011;164:1403-1405. PMID: 21564053.
- [pubmed] Devlin J, et al. "Melanotan II overdose associated with priapism." Clin Toxicol (Phila), 2013;51(4):383. PMID: 23537392.
- [pubmed] Langan EA, et al. "Melanotropic peptides: more than just 'Barbie drugs' and 'sun-tan jabs'?." Br J Dermatol, 2010;163(3):451-5. PMID: 20545686.
Sources & Citations
Every citation on this page is PubMed-indexed and has been checked against its record, except a 2010 commentary we could not match to a PubMed record. Five References entries carry no card: two original erectile-dysfunction trials and a risk review, indexed by PubMed under melanotan-II but not naming it in their titles, and two letters with no abstract, for which this page states nothing beyond their titles. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.