Melanotan 1 vs 2: How the Two Tanning Peptides Compare (2026)

Melanotan 1 and Melanotan 2 come as the same white powder in the same 10mg vial, carry almost the same name and are bought for the same reason: a tan. Both were made by one University of Arizona research group in the 1980s, as long-lasting copies of the hormone that darkens skin. Then they went separate ways. One became an approved drug for a rare light-sensitivity disorder; the other became the tanning peptide most buyers know by name, and the starting point for a libido drug.

Simms Research sells both, Melanotan I and Melanotan II, as 10mg vials for $55 each. The choice rests on how fast and how deep a tan the research needs, and how much of Melanotan 2’s extra activity it can carry.

What are Melanotan 1 and Melanotan 2?

Both are synthetic versions of alpha-MSH, the hormone that tells pigment cells in the skin to make melanin, built to outlast the natural hormone and bind harder.

Melanotan 1, also called afamelanotide or MT-1, keeps the full 13-amino-acid chain of alpha-MSH with two swaps: norleucine at position 4 and D-phenylalanine at position 7. Those changes make it far more stable and potent at MC1R, the pigment receptor. As a 16mg implant placed under the skin every two months, afamelanotide is the drug Scenesse, approved in Europe in 2014 and in the US in October 2019 for erythropoietic protoporphyria, an inherited condition that makes sunlight painful.

Melanotan 2, or MT-2, is shorter and closed into a ring: seven amino acids, two of them bridged. The ring keeps it compact and stable and lets it act on melanocortin receptors 1, 3, 4 and 5, not mainly the pigment receptor. It went through small human trials for tanning and for erectile dysfunction in the 1990s but never reached an approval of its own.

What is the difference between Melanotan 1 and 2?

Receptor reach. Both switch on MC1R, the receptor on pigment cells that drives melanin. Afamelanotide “binds predominantly to MC1-R”, in the words of its US label, and in its trials what it did showed up in the skin. Melanotan 2 also acts strongly on MC3R and MC4R, the melanocortin receptors that help set appetite and sexual response, so its effects reach well beyond the skin.

That one difference explains nearly everything buyers notice. Melanotan 2 is the stronger tanner per microgram: in the Arizona trials it darkened skin at a fraction of Melanotan 1’s dose, and five doses were enough. It also reaches further. Nausea and flushing come more often, and yawning, lower appetite and spontaneous erections come with them, the last of which led to PT-141. Melanotan 1 is the quieter of the two. It needs more peptide and more time, and its record shows little beyond the tan, some nausea and flushing.

Melanotan 1 vs 2 side by side

How the pair compares line by line, down to the Simms Research vials:

Melanotan 1 vs 2 results: how fast each one tans

Melanotan 2 tans faster and darker; Melanotan 1 builds a lighter, more even tan over more weeks.

In the first Melanotan 1 tanning trial, published in JAMA in 1991, 28 men took ten injections over 12 days and wore high-potency sunscreen the whole time. Skin darkened in fair men who burn easily and in olive-skinned men who tan well, kept darkening after the last dose and peaked one to three weeks later, three to five weeks from the start. Melanotan 2 got there on less. In its 1996 pilot, five low doses given every other day darkened the face, upper body and buttocks of two of three men, measured a week after the course ended.

Melanotan 2 before-and-after reports follow a set order. Freckles and existing moles darken first, sometimes within a day or two of the first dose, then the face, shoulders and arms, with the overall tone deepening across the first two to three weeks. Melanotan 1 follows the same order more slowly, which is why its before-and-after sets are usually a month or more apart.

Does Melanotan 1 or 2 work without sun?

Both tan without sun, and both tan more with it. Afamelanotide raises eumelanin “independently of exposure to sunlight or artificial UV light sources”, its US label states, and the 1991 trial darkened men who wore sunscreen throughout.

Sunlight multiplies the effect. In a 2004 University of Arizona study, people given Melanotan 1 with sunlight tanned more deeply than a sun-only group, held the tan at least three weeks longer, and the sun-only group needed 50% more time in the sun to match them. In the same program, Melanotan 1 cut sunburn cells at the exposed skin by 47%.

Melanotan 2 darkened the buttocks in its 1996 pilot, skin that rarely sees the sun, so it works without it too. It still shows color fastest with some UV, which is why Melanotan 2 protocols pair the loading weeks with short sun sessions; the Melanotan 2 dosage guide covers how.

Melanotan 1 vs 2 for libido and appetite

Only Melanotan 2 has libido and appetite effects on record. In a 1998 crossover trial at the University of Arizona, 8 of 10 men with erectile dysfunction of no physical cause developed erections after Melanotan 2, and firm erections lasted 38 minutes on average against 3 on placebo. A 2000 follow-up in men with physical causes found raised sexual desire as well, and the 1998 trial recorded lower appetite, nausea, stretching and yawning more often than placebo. These are MC4R effects, and none of them appears in Melanotan 1’s trials.

PT-141, bremelanotide, was developed from Melanotan 2 for the libido effect and became its own approved drug in 2019, for low sexual desire in premenopausal women. Simms Research sells PT-141 as a separate 10mg vial for $64, a different molecule from the Melanotan 2 vial.

Lower appetite is where the Melanotan 2 weight-loss question comes from. In rats it cuts food intake sharply through MC4R, but no human study has measured weight loss on it.

Melanotan 1 vs 2 side effects

Most effects from either are mild and pass within hours: nausea and facial flushing after a dose. The difference is how often they come, and how much is on record.

Melanotan 1 has the larger and cleaner record. In the three placebo-controlled trials behind its US approval, 244 adults over six months, four in five people on afamelanotide had no nausea at all: it reached 19%, against 14% on placebo. Implant-site reactions ran 21% against 10%, and nothing else passed 7%. The Arizona tanning trials of the injected peptide recorded only nausea and passing facial flushing.

Melanotan 2’s record is small trials, and nausea runs through them: mild nausea at most dose levels in the 1996 pilot, none needing treatment, and severe nausea after 4 of 19 injections in the 2000 trial, at a dose several times the draws protocols use now. Flushing, yawning and stretching, lower appetite and spontaneous erections make up the rest.

Moles and freckles

Both darken freckles and existing moles; that is the pigment response, and afamelanotide’s label lists it. New moles are where they part. Afamelanotide’s trials reported moles as a side effect in 4% against 2% on placebo. Melanotan 2 has case reports of small new moles appearing during use, and a 2019 review of 179 cases of these eruptive moles lists melanotan among the drugs behind them. Darkening fades after the peptide stops, as the tan does; brand-new moles mostly stay, though some fade too.

On the record, then, Melanotan 1 is the better-documented of the two: an approved drug’s trials against Melanotan 2’s pilots and case reports.

Melanotan 1 vs 2 dosage

Both mix the same way: 2mL of bac water in the 10mg vial puts 500mcg behind every 10 units of a U-100 syringe. What differs is the draw. Melanotan 1 protocols take up to twice as much per dose, so the same vial covers half as many loading days:

Melanotan 2’s full chart, with first draws, skin type and timing, is in the Melanotan 2 dosage guide. For any other dose, the peptide calculator works out the units, and how to reconstitute peptides walks through the mixing. A 10mL vial of Research Water, Simms Research’s bac water at $20, is enough for five 2mL mixes (the bac water guide explains why). Either peptide lasts 28 days refrigerated once mixed, and the peptide storage guide covers the vial before and after mixing.

Which is better, Melanotan 1 or 2?

For a tan with the fewest extra effects, Melanotan 1. For the fastest, deepest tan from the smallest draws, Melanotan 2.

Choose Melanotan 1 when the research is about pigment and nothing else. It has an approved drug’s safety record behind it, its trials show little beyond nausea and flushing, and it brings no libido or appetite effects into the results. The trade is time and peptide: bigger draws, a vial that covers 10 to 20 loading days, and a tan that builds over weeks, best with some sun.

Choose Melanotan 2 when speed and depth matter more than a quiet profile, or when the research takes in appetite or sexual response through MC3R and MC4R. Expect nausea and flushing in the first draws, and darker freckles and moles sooner.

Not both at once. Melanotan 2 already acts on MC1R, so adding Melanotan 1 brings no new receptor, and no study has paired them.

What the Melanotan 1 and 2 batch reports show

Both came in above the 10mg on the label, at over 99.5% purity. An independent ISO-certified lab tested the current batch of each on July 16, 2026, three vials apiece. Melanotan 1 averaged 11.45mg at 99.576% purity, 11.14 to 11.68mg across its vials, and Melanotan 2 averaged 10.82mg at 99.679%, 10.12 to 11.43mg. Mass spectrometry matched each to its molecule, and each cleared endotoxin, heavy-metal and sterility screens.

In practice, a vial mixed as if it held exactly 10mg gives about 14% more Melanotan 1, or 8% more Melanotan 2, per unit than the dosage table says. Each also has an April 2026 batch, tested on a single vial for identity, purity, content and endotoxins: Melanotan 1 at 99.47% and 11.03mg, Melanotan 2 at 99.29% and 10.43mg. The full certificates sit on the Melanotan I lab results and Melanotan II lab results pages and in the full lab results library, and How to Read a Peptide Certificate of Analysis walks through what each line means.

Frequently asked questions

Do you need to tan with Melanotan 1?

No. In the 1991 trial it darkened men who wore sunscreen throughout, and its label says it works without sun or UV. Sunlight deepens the tan and makes it last: in 2004 it saved a third of the sun time needed for the same color.

How long does it take to see Melanotan 1 results?

Two to four weeks for visible color on most protocols. In the 1991 trial, skin darkened across 12 days of doses and kept going, peaking one to three weeks after the last.

Do moles from Melanotan 2 go away?

Darkened moles lighten again once it stops, as the tan fades. Brand-new moles mostly stay, though case reports describe some fading too.

How long does Melanotan 2 take to tan?

One to two weeks of loading for visible color on medium skin, longer on very fair skin, and freckles first. The Melanotan 2 dosage guide breaks it down by skin type.