Melanotan 2 is an injectable peptide that makes your skin tan without sun exposure. People take it to get darker, faster, with less time in the sun or on a sunbed. It works, and that's why it has a following. A few weeks of small subcutaneous injections will visibly darken most skin, and the effect holds as long as you keep dosing.
The catch is that it doesn't only hit the receptor that controls pigment. The same molecule also triggers spontaneous erections, appetite suppression, nausea, and facial flushing, and over time it darkens moles and freckles along with the rest of you. It's a research chemical with no approved version for tanning anywhere, so everything sold is grey-market. Most of what we know about real-world effects comes from user reports and case studies in dermatology clinics, not clean trials.
Deep-dive
Melanotan 2 (MT-2) is a synthetic cyclic analog of alpha-melanocyte-stimulating hormone (alpha-MSH), the natural hormone your body releases to drive pigmentation. The synthetic version is more potent than the natural peptide and resists being broken down, so a small dose does a lot. It was first developed at the University of Arizona in the 1980s and 90s as a way to induce a protective tan without UV exposure, and an early phase I study in three volunteers confirmed that subcutaneous injection darkened the skin. It was never developed into an approved drug. A more selective cousin, melanotan 1 (afamelanotide), went through proper trials and is approved for a rare light-sensitivity disorder. MT-2 itself stayed in the grey market.
How the tan actually happens. MT-2 binds the melanocortin-1 receptor (MC1R) on melanocytes, the pigment-producing cells in your skin. That switches on the cAMP pathway inside the cell, which ramps up tyrosinase, the rate-limiting enzyme for making melanin, and shifts production toward eumelanin, the darker, more photoprotective pigment. The result looks like a UV tan but is driven chemically from the inside rather than by sun damage on the outside. Worth being precise here: MT-2 also stimulates melanocytes to proliferate, not just to make more pigment. That is the same cell population that turns malignant in melanoma, which is the mechanistic root of the safety concern further down.
Why it does so much more than tan. MT-2 is non-selective. It activates not just MC1R but also MC3R, MC4R, and MC5R. MC4R in the hypothalamus is the one responsible for the sexual effects, MT-2 is a potent initiator of erections and increases sexual desire, and MC4R activation also drives the appetite suppression and nausea. 
PT-141 (Bremelanotide), the FDA-approved libido drug, was created by chemically modifying MT-2 to keep the MC4R activity and strip out most of the MC1R pigment activity. So MT-2 is essentially "PT-141 plus a tan" from the user's point of view, but with the full melanocyte-stimulating risk profile attached. If sexual effect is what you're after and tanning isn't, PT-141 is the more targeted tool and is covered on its own page.
What the human evidence actually consists of. This is important context. There are no completed modern phase 3 trials for cosmetic tanning. The clinical evidence is a handful of small phase I pharmacology studies from the 1990s, plus the erectile-dysfunction crossover studies, plus a large and growing pile of case reports documenting harms. The original phase I tanning study used only three men. The erectile dysfunction crossover study used 20 men and found MT-2 produced erections in 17 of 20 without any sexual stimulation, with nausea and yawning as the standout side effects. Everything about long-term tanning use, the dose people actually run, the cycling patterns, comes from community practice, not from data. That's the honest state of the evidence: the tanning works and the acute side effects are well documented, but nobody has run the long study that would tell you whether years of use is safe.
Women. MT-2's pigment mechanism works the same way in women, MC1R biology isn't sex-specific, and women make up a large share of real-world tanning users. The sexual effects also apply: MT-2 increases sexual desire and genital arousal in women, not just men. This isn't a footnote, it's the basis of an entire drug class. The discovery that melanocortins drive female desire led directly to PT-141 being developed and FDA-approved for hypoactive sexual desire disorder in premenopausal women. A randomised neuroimaging study in 31 premenopausal women with HSDD found MC4R agonism increased sexual desire for up to 24 hours and changed how the brain processed erotic stimuli. Practically, women report the same flushing, nausea and appetite drop as men, and the same mole-darkening concern applies equally. Women considering it should know the libido effect is real and can be unwanted, not just a male side effect. There is no safety data in pregnancy or breastfeeding, so it should be avoided there outright.
The mole problem, in detail. Because MT-2 stimulates melanocytes everywhere, existing moles and freckles get darker, and case reports describe new moles appearing during use. Dermatology journals have documented eruptive new moles and darkening of existing ones within 24 hours of a single injection, atypical (dysplastic) moles appearing after a course of MT-2, and at least four published cases of melanoma diagnosed during or shortly after MT-2 use. A causal link to melanoma is not proven, the cases are too few and people who tan chemically also tend to tan in other risky ways, but the mechanism is real and the signal is consistent enough that this is the single most important downside to take seriously. The practical problem is also diagnostic: MT-2 changes the appearance of moles, which makes it harder for you or a dermatologist to spot a genuinely dangerous lesion against the noise of drug-induced changes.
The systemic toxicity case reports. Beyond the skin, the non-selective receptor activity has been linked in case reports to serious events, mostly at higher or contaminated doses. These include rhabdomyolysis and renal dysfunction with sympathomimetic toxicity, ischemic priapism requiring surgical intervention, posterior reversible encephalopathy syndrome, and renal infarction. These are rare and individually they're single cases, not population-level risk estimates. But they share a theme: a peptide hitting multiple receptor systems at once, often combined with unregulated product of unknown purity and dose. The grey-market supply chain is part of the risk here, not separate from it.
Dosage:
- MT-2 comes as a lyophilised powder that you reconstitute with bacteriostatic water and inject subcutaneously. Dosing below is what the user community converges on, not trial-validated protocol
- Loading phase: roughly 0.25 mg per day to start, building toward your visible tan over 1 to 3 weeks. Many people start lower, around 0.1 mg, to gauge nausea tolerance before going up
- Maintenance phase: once you've reached the colour you want, roughly 0.5 to 1 mg once or twice per week is enough to hold it. The tan fades over weeks if you stop
- Start low regardless of sex or size. Nausea, flushing and appetite suppression are dose-dependent, and the lowest effective dose is the goal, more is not better and does not tan you faster in any way worth the side effects. Smaller individuals and anyone sensitive to nausea should sit at the bottom of the range
- Timing: evening dosing is common because it lets you sleep through the nausea and flushing peak. Some sun or sunbed exposure speeds visible results, but it is not required for the tan to develop, and stacking heavy UV on top of a melanocyte-stimulating drug compounds the risk
- Women: same dosing logic, no separate dose scale, but be aware the libido effect tracks with dose too, so a lower maintenance dose also keeps that milder if it's unwanted
- Reconstitution and storage: keep reconstituted peptide refrigerated and use clean technique. Product purity is unverifiable on the grey market, which is itself a dosing problem, you don't truly know what's in the vial
Here's what you can expect:
The tan builds gradually. Most people see noticeable colour within 1 to 2 weeks of daily low dosing and a full tan over 3 to 4 weeks, then hold it with occasional maintenance doses. The colour fades over several weeks once you stop. Fair-skinned people see the biggest visible change.
The side effects show up faster than the tan. On the first few injections, expect facial flushing, mild nausea, and spontaneous yawning or stretching within an hour or two of the dose, this is the most consistent thing users report. Appetite often drops. Men frequently get spontaneous erections, especially early on, and women often report increased libido, both can be stronger than expected. These acute effects usually settle as your body adjusts over the first week or two, which is the main reason people push through.
Moles and freckles darkening is the change to actually watch. It is common, often partly permanent for moles, and it is the reason a baseline skin check matters.
Side effects & risks:
- Nausea, facial flushing, and spontaneous yawning or stretching are the near-universal acute effects, worst in the first few doses and after each dose increase. Usually settle with time and lower doses
- Appetite suppression via MC4R. Some people consider this a bonus, but unintended weight loss happens
- Spontaneous erections in men, increased libido in both sexes. Driven by MC4R. Can be unwanted or come at inconvenient times. In rare case reports, MT-2 has caused priapism, a prolonged painful erection that is a medical emergency
- Darkening of moles and freckles, and new moles appearing. Documented across multiple dermatology case reports. Often partly permanent. This also makes genuine skin cancer harder to spot against the background of drug-induced changes
- Melanoma concern. MT-2 stimulates melanocytes to proliferate, the same cells involved in melanoma, and at least four published cases describe melanoma during or after MT-2 use. Causation is not established, but the mechanism is plausible and this is the most serious theoretical risk. A personal or family history of melanoma or dysplastic naevi is a strong reason not to use it
- Melanonychia, brown to black pigment bands appearing in the nails
- Rare serious systemic events. Case reports link MT-2, usually at higher or contaminated doses, to rhabdomyolysis and renal dysfunction, posterior reversible encephalopathy syndrome, and renal infarction
- Contamination and dosing uncertainty. Everything sold is unregulated. Purity, sterility, and actual peptide content are unverifiable, and shared or non-sterile needles add infection risk on top of the drug itself
- Blood pressure. Melanocortin agonists can affect blood pressure and heart rate, worth a baseline reading if you have any cardiovascular history
- Pregnancy and breastfeeding: avoid. No safety data
Blood markers
Full-body skin check by a dermatologist, baseline before you start. This isn't bloodwork but it's the single most important test here. You want a documented map of your moles before MT-2 changes how they look, so that future changes can be judged against a real reference. Recheck every 3 to 6 months while using, and have anything genuinely changing in size or shape assessed properly.
Blood pressure and heart rate, baseline. Melanocortin agonists can shift both. Get a reference point before starting, especially with any cardiovascular history.
Kidney function (creatinine, eGFR) and CK, baseline if you plan to run higher doses or use it long-term. The serious case reports cluster around renal injury and rhabdomyolysis, so a baseline gives you something to compare against if you ever feel unwell on it.
Who actually needs what: everyone using MT-2 should get the baseline skin check, it's non-negotiable given the mechanism. Blood pressure is a quick, cheap baseline worth having. Kidney and CK testing matters most for higher-dose or long-term users and anyone with existing kidney or cardiovascular issues. Anyone with a personal or family history of melanoma or atypical moles should treat that as a reason not to use it at all rather than something to monitor around.
Sold as an unregulated research chemical.
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