A synthetic melanocortin agonist sold online as an unregulated tanning peptide. Public health agencies in multiple countries have warned consumers against it. We cover it because it's widely searched, not because the use case is supported.
Important: Melanotan II carries documented safety concerns
Public health agencies including the UK Medicines and Healthcare products Regulatory Agency (MHRA), Australia's Therapeutic Goods Administration (TGA), and the U.S. Food and Drug Administration have issued consumer warnings against Melanotan II products. Reported adverse events include priapism (prolonged painful erection requiring emergency care), severe nausea, blood-pressure changes, and case reports of melanoma occurring in users. The compound has not gone through the clinical-development process that would establish a safe-use profile.
This page exists for educational completeness. Anyone considering Melanotan II should be aware that it operates entirely outside any regulatory framework, that the products sold online are not quality-controlled, and that the safety literature is meaningfully concerning. If you have any of the conditions discussed on this page, talk to a licensed clinician.
The 30-second read
Melanotan II is a synthetic peptide that activates melanocortin receptors, especially MC1R (which controls skin pigmentation) and MC4R (which affects appetite and sexual response). It produces tanning without UV exposure and was originally developed as a research compound at the University of Arizona in the 1980s. It was never approved as a drug. The compound is sold online in unregulated channels for tanning, and is also informally used for sexual-response effects (which led to the development of bremelanotide / PT-141, the FDA-approved descendant). The safety record is concerning: documented reports of priapism, nausea, blood-pressure spikes, melanoma cases in users, and the compounded products themselves vary in identity and purity.
Why this is on people's radar
Melanotan II has been in informal use for nearly twenty years. The original research at the University of Arizona explored it as a potential treatment for skin conditions and as a way to induce protective tanning in fair-skinned people at high skin-cancer risk. Clinical development for those medical applications was abandoned, but the compound, easy to synthesize and easy to use, moved into informal "research peptide" channels and online tanning-product markets.
The cultural footprint expanded beyond tanning when users noticed prominent sexual-response effects (libido and erection). That observation led to clinical development of a related compound, bremelanotide (PT-141), which was eventually FDA-approved in 2019 for hypoactive sexual desire disorder in premenopausal women. Bremelanotide is the regulated, approved descendant of the Melanotan II line of research; Melanotan II itself never went through that process.
Public-health agencies in the UK, Australia, Norway, and other countries have repeatedly warned consumers against Melanotan II products, citing safety concerns and the unregulated nature of the supply. The FDA in the U.S. has also issued warnings. Despite this, the compound has remained in informal use, and is what most readers are searching for when they look up "melanotan."
A note on framing this page
For most peptides on this site, we have a "what people are usually trying to do with it" section, three or four plain-language goals readers might recognize. We're handling Melanotan II differently. The implied use cases (tanning without sun, sexual-response effects) are not supported by clinical-grade evidence, and framing them as plausible goals would understate how unsettled the safety picture is.
What we will say: people search for this compound for tanning effects and for sexual-response effects. Both have been documented in users. Neither has been studied in a clinical-trial framework that would establish a safe-use profile, and both come with documented adverse events. The clinical development that did continue, bremelanotide / PT-141 for sexual desire, is the regulated path forward in this corner of pharmacology.
What the science actually shows
Plain-English summary of the literature:
Tanning effects are real, mechanism is established
Melanotan II activates MC1R on melanocytes, stimulating melanin production. Skin darkening following injection has been reported consistently in users and in early clinical work. The mechanism is well understood.1
Sexual-response effects led to a different drug
The libido and erection effects reported in early Melanotan II work led to clinical development of bremelanotide (PT-141), which was FDA-approved in 2019 (Vyleesi) for premenopausal HSDD. Bremelanotide is the regulated, studied successor to this line of compounds.2
Priapism is a documented adverse event
Multiple case reports describe priapism (sustained painful erection requiring emergency intervention) in Melanotan II users. This is a recognized risk of melanocortin-receptor agonism in this dose range.3
Melanoma case reports are concerning
The medical literature contains case reports of new melanomas and changing nevi in Melanotan II users. Whether the compound is causally linked to these events or selecting for a population already at higher risk hasn't been definitively established, but the case-report signal exists.4
Other adverse events are common
Nausea, flushing, blood-pressure fluctuations, GI upset, spontaneous erections, and changes in appetite are reported regularly. Severe reactions including kidney injury and rhabdomyolysis have been reported in case literature.5
Product identity and purity are not regulated
Products sold as Melanotan II in online channels are not subject to identity or purity testing. Several published analyses of online-sourced products have found variable peptide content, contaminants, or different compounds entirely.6
The honest read
What's solid:
The mechanism of Melanotan II at melanocortin receptors is well characterized. Tanning effects in users are real. The line of research did produce a legitimate, FDA-approved drug, bremelanotide / PT-141, for sexual desire disorder.
What's still being worked out:
Whether the melanoma case reports reflect a causal relationship with the compound or selection of an already at-risk population. Whether long-term use carries cumulative risks beyond what acute case reports suggest. The absence of clinical-grade trials means many basic safety questions remain unanswered.
What's hyped beyond the evidence:
The framing of Melanotan II as a "safe sunless tan." The compound has not gone through the clinical-development pathway that would establish that profile, agencies in multiple countries have warned against it, and the documented adverse-event list is meaningfully concerning. The regulated successor compound for the sexual-response use case (bremelanotide) exists and went through FDA review for a reason.
Things to know if you're researching this compound
Public-health warnings exist: the UK MHRA, Australia TGA, Norwegian Medicines Agency, and FDA have all issued warnings against Melanotan II products.
Distinct from Melanotan I: Melanotan I (afamelanotide / Scenesse) is FDA-approved for the rare condition erythropoietic protoporphyria. Melanotan II is a different molecule and is not approved.
Distinct from PT-141 / bremelanotide: Bremelanotide (Vyleesi) is the FDA-approved descendant peptide for sexual desire disorder in premenopausal women. It is the regulated path forward in this molecular family.
Priapism is a recognized risk: sustained erection beyond a few hours is a urological emergency. This adverse event is documented in users.
Melanoma surveillance: any new or changing pigmented skin lesion warrants prompt dermatology evaluation. Users should be especially cautious here.
Product identity is uncontrolled: what's actually in vials sold as Melanotan II varies. Independent analyses have found inconsistent content.
Mechanism, dosing, and references: in the "Want to go deeper?" section below.
Reconstitution & dose reference
Read this before going further.
Melanotan II is the most safety-concerning peptide on this site. Documented serious adverse events in actual users include priapism (sustained painful erection requiring emergency care), case reports of new or changing melanomas, severe nausea, blood-pressure spikes, kidney injury and rhabdomyolysis, spontaneous yawning and stretching reactions, and inconsistent product identity in unregulated supply. The FDA, UK MHRA, Australia TGA, and Norwegian Medicines Agency have all issued consumer warnings against Melanotan II products. This is not a peptide where the dose math is the main risk — the compound itself is.
The dose math below is provided for harm-reduction reference only — not as a recommendation. The numbers reflect what's circulating in research-peptide community sources, not validated clinical doses (no clinical-development program ever completed). The deeper dosing section on this page deliberately does not provide a protocol for the same reasons. We're including the math here so people who are going to use this anyway have access to the numbers and the safety information together rather than separately. We do not endorse using Melanotan II.
Stop immediately and seek emergency care if:
Sustained painful erection lasting more than 2 hours — this is priapism. Urology emergency. Tissue damage starts within hours; permanent erectile dysfunction is a real risk.
New or changing moles, dark spots, or pigmented lesions — stop and see a dermatologist promptly. Get a baseline full-body skin check before any use; recheck after any cycle.
Severe persistent nausea, vomiting, or fainting — especially if accompanied by blood-pressure changes.
Dark or reduced urine, severe muscle pain, fatigue — signs of rhabdomyolysis or kidney injury, both documented in user case reports.
Severe headache, vision changes, or chest pain — cardiovascular adverse events are documented.
Community loading start
200 mcg/day
Lowest entry; assess tolerance carefully
Community loading range
250–500 mcg/day
Daily until target pigmentation reached
Community max
1000 mcg/day
Side-effect risk increases sharply above this
Maintenance
500–1000 mcg
1–2× weekly after loading
mL
Defaults to 5 mg/mL (2 mL into the 10 mg vial), the standard community reconstitution. Standard 200 mcg loading dose lands at 4 syringe units; 500 mcg at 10 units. For better small-dose precision, reconstitute with 4 mL water (2.5 mg/mL) and the units roughly double.
mcg
Subcutaneous injection. Loading phase is daily for 4–8 weeks; maintenance is 1–2× weekly. This is not a recommendation. The duration estimate below assumes daily loading. Inject in the evening after eating — severe nausea is the most common acute side effect and is worse on an empty stomach.
Above community-reported use. Daily doses above 1000 mcg sharply increase side-effect risk — nausea, blood pressure changes, and the priapism risk all scale with dose. There is no clinical evidence supporting any benefit from higher doses; the original University of Arizona research that established a dose range topped out around 1 mg.
Concentration
5.0 mg/mL
Per dose
0.04 mL
4 units on insulin syringe
Doses per vial
~50
~50 days (~7.1 weeks) of daily loading
Harm-reduction guidance — the most important section on this calculator
Get a full-body skin check from a dermatologist before any use. Establish a baseline of every existing mole and pigmented lesion you have. Photograph any concerning ones. The case-report literature on melanoma in MT-2 users is the single most-concerning safety signal, and you cannot detect a "new or changing lesion" later if you don't know what your skin looked like first. This step is non-negotiable for anyone going forward.
Start at 200 mcg, not 500 mcg or 1 mg. The first doses are when nausea, blood-pressure changes, and priapism are most likely. Most acute adverse events happen during loading. The lowest community starting dose exists for a reason.
Inject in the evening after a full meal. Severe nausea is the most common acute side effect. Empty-stomach injection makes it worse. Evening timing also lets you sleep through the worst of the acute response if it hits.
Do not increase the dose just because you don't see tan results yet. Pigmentation builds slowly — weeks, not days. Side effects scale with dose. Pushing the dose up early in pursuit of faster results is the most reliable way to hit a serious adverse event without proportional benefit.
Stop loading at 4–8 weeks regardless of result. Continuous high-dose loading isn't supported by the original research and increases the cumulative-exposure question that underlies the cancer-biology concern. Move to maintenance (500–1000 mcg, 1–2× weekly) once tan develops, or stop entirely if it doesn't.
Do not use if you have: personal or strong family history of melanoma or other skin cancers, history of priapism or other erection-related conditions, uncontrolled blood pressure, kidney disease, pregnancy or trying to conceive, or any new pigmented lesion you haven't shown a dermatologist. Each of these is a hard contraindication, not a "use with caution."
If you choose to use, use the FDA-approved descendants instead where possible.PT-141 / bremelanotide (Vyleesi) is the FDA-approved descendant for the sexual-response use case. Melanotan I / afamelanotide (Scenesse) is the FDA-approved descendant for protected pigmentation in a specific medical condition. Neither is a perfect substitute for what MT-2 users typically want, but both have actual clinical-development evidence and quality-controlled supply.
The honest read. MT-2 is the only peptide on this site where the dose math is genuinely secondary to the compound's safety profile. Calculating the "right" dose doesn't make MT-2 safer; it just makes the dosing unit smaller. The case reports of priapism, melanoma, rhabdomyolysis, and cardiovascular events are documented in actual users, not theoretical concerns from animal studies. Multiple national health agencies have warned against the compound. The original academic work was discontinued. The dose math is included on this calculator only because the alternative — people doing the math without the safety information — is worse, not because we think the dose math itself is the protective factor.
For educational and harm-reduction purposes only. This is not medical advice and is not dosing guidance. Melanotan II is not FDA-approved for any indication and has documented serious adverse events including priapism, melanoma case reports, kidney injury, and cardiovascular effects. The FDA, UK MHRA, Australia TGA, and Norwegian Medicines Agency have issued consumer warnings against Melanotan II products. We include this calculator so the dose math is at least clear and paired with safety information for people determined to use this compound anyway; we do not endorse using it. Consult a licensed healthcare provider before any health decision, and a dermatologist for skin surveillance baseline.
What people often ask
What's the difference between Melanotan I and Melanotan II?
They're different molecules with different receptor selectivity. Melanotan I (afamelanotide / Scenesse) is FDA-approved for erythropoietic protoporphyria, a rare light-sensitivity disorder. Melanotan II is structurally different, not FDA-approved, and has a broader receptor activation profile that drives the sexual-response and adverse-event side. Melanotan II is what most people mean when they search for "melanotan."
Is it the same thing as PT-141?
No. PT-141 (bremelanotide / Vyleesi) is a related, FDA-approved peptide developed for sexual desire disorder in premenopausal women. It's a separate molecule that went through clinical development. PT-141 has its own page on this site.
Is Melanotan II legal?
It's not FDA-approved as a drug. Selling it for human use is illegal in many countries. It's often sold online with disclaimers calling it "research-only" or "not for human consumption", these labels are how vendors operate in legal grey zones, but they don't make the products safer or more regulated.
Does it actually cause melanoma?
The medical literature contains case reports of melanoma and changing pigmented lesions in Melanotan II users. Whether the relationship is causal or whether users are a population already at higher melanoma risk hasn't been definitively established. The case-report signal is there and is taken seriously by dermatologists.
Why is this page on the site if you're warning people away from it?
Because people search for it, and a "peptides explained honestly" site that pretends Melanotan II doesn't exist isn't being honest. The right answer to the question "what is this?" is "here's what it is and here's why public-health agencies are concerned about it", not silence.
FDA and regulatory status
Status as of May 5, 2026: Melanotan II is not FDA-approved for any indication. The FDA, the UK MHRA, Australia's TGA, and other national agencies have issued consumer warnings against Melanotan II products. The related compound bremelanotide (Vyleesi / PT-141) is FDA-approved for hypoactive sexual desire disorder in premenopausal women. The other related compound afamelanotide (Scenesse / Melanotan I) is FDA-approved for erythropoietic protoporphyria. Status updates land here when they happen.
Want to go deeper?
Mechanism, the melanocortin receptor system, and references.
Background
Melanotan II is a cyclic heptapeptide synthetic analog of α-melanocyte-stimulating hormone (α-MSH). It was developed at the University of Arizona in the 1980s under the direction of Mac Hadley and Victor Hruby as part of a research program exploring melanocortin-receptor agonists as protective tanning agents and treatments for sexual dysfunction. The compound has the structure Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2.
Mechanism of action
Melanotan II is a non-selective agonist at melanocortin receptors. Its primary clinical-relevant activities are at MC1R (peripheral, on melanocytes, drives melanin production) and MC4R (central, in hypothalamus, drives appetite suppression and sexual response). It also has activity at MC3R and MC5R. The non-selective profile is a key reason adverse events span tanning, GI, sexual-response, and cardiovascular domains. The FDA-approved descendant compound bremelanotide retains MC4R activity for the sexual-desire indication while having a different overall pharmacologic profile.
Adverse-event profile in the literature
The published literature on Melanotan II adverse events includes priapism case reports, dermatologic concerns including new melanomas and changing nevi in users, GI symptoms (severe nausea common), blood-pressure fluctuations, spontaneous yawning and stretching reactions, kidney injury including rhabdomyolysis, and renal failure case reports. Product-quality literature documents inconsistent identity and purity in online-sourced products.
Dosing context
This site does not provide dosing protocols for unregulated compounds with documented safety concerns. Published academic-research dosing existed in the original University of Arizona work, but that work was discontinued and the compound was never approved for human use. Anyone with questions about the compound should consult a licensed clinician.
References
Dorr RT, et al. (1996). "Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study." Life Sci, 58(20), 1777–1784. PubMed
Kingsberg SA, et al. (2019). "Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials." Obstet Gynecol, 134(5), 899–908. PubMed
Brennan R, et al. (2008). "Use of melanotan I and II in the general population." BMJ, 337, a2748. PubMed
Habbema L, et al. (2017). "Risks of unregulated use of alpha-melanocyte-stimulating hormone analogues: a review." Int J Dermatol, 56(10), 975–980. PubMed
Breindahl T, et al. (2015). "Identification of synthetic peptides in counterfeit drug products." Various analytical-chemistry case reports of online-sourced products. PubMed
U.S. Food and Drug Administration. "Tanning Pills." Consumer health information. FDA.gov
UK Medicines and Healthcare products Regulatory Agency. "Melanotan products: warnings to consumers." MHRA
For educational and research purposes only. This is not medical advice. Melanotan II is not FDA-approved and has documented safety concerns including priapism, melanoma case reports, and adverse events affecting multiple organ systems. PeptideLibraryHub is independent and does not sell peptides or accept money from anyone who does.