What Is Melanotan II? Dosage, Half-Life & How to Track It

What Melanotan II is and how it works

Melanotan II is a synthetic peptide built to mimic α-MSH, the hormone that normally tells melanocytes (the skin’s pigment-producing cells) to make more melanin. Because it works on the melanocytes directly, it darkens skin without needing UV exposure the way natural tanning does — though many users still combine it with some sun exposure to “kick-start” the process.

It is not a selective drug. Alongside the MC1R activity that drives pigmentation, it also hits MC3R and MC4R — the same receptors involved in appetite and sexual arousal. That crossover is not a side effect in the usual sense; it is the same mechanism that produced the erectile-activity finding that led researchers to isolate PT-141 (bremelanotide) as a more targeted follow-on compound. MT-2 itself has never been developed into an approved drug.

Because the effect is systemic rather than local, it tans skin fairly evenly, including areas that rarely see sun — part of why the FDA has issued specific warnings about unapproved “tanning peptide” products.

Typical dosing & reconstitution

A common titration starts low to manage nausea and works up over several weeks: roughly 250 mcg on day one, 500 mcg by week two, 750 mcg by week three, and 1,000 mcg daily through the loading phase (about 8 weeks total). Once pigmentation reaches the desired level, maintenance typically drops to 500–1,000 mcg, once or twice a week, rather than daily.

Melanotan II comes as a lyophilized powder:

At 3.33 mg/mL, the day-one 250 mcg dose is about 7–8 units, and the 1,000 mcg maintenance dose is 30 units on a U-100 insulin syringe. Reconstituted MT-2 is generally used within 1–2 weeks refrigerated.

Half-life & what it means for frequency

Melanotan II’s elimination half-life is roughly 2 hours based on early clinical pharmacokinetic studies, which is why the loading phase is dosed daily — a single injection doesn’t linger long enough to build pigmentation on its own. Once melanin production is established, though, the pigment itself persists in the skin far longer than the peptide does, which is what lets maintenance dosing drop to once or twice a week.

That gap between the peptide’s short half-life and the tan’s much longer visible persistence is the whole logic of the loading-then-maintenance structure — you are not trying to keep the peptide circulating, you are trying to keep melanocyte activity elevated often enough to sustain the pigment already produced.

What to track & common side effects

Side effects are common, especially early in the loading phase: nausea and flushing (often worst with the first few doses and easing with continued use), spontaneous erections in men, appetite suppression, and darkening or changes to existing moles. That last one is the most important to take seriously — because MT-2 stimulates melanocyte activity broadly, dermatologic monitoring for new or changing moles is a genuine, documented caution, not a theoretical one.

What’s worth tracking: dose through the titration (since nausea tends to correlate with how fast you ramp), any change in existing moles (worth photographing over time), and the maintenance schedule once you’ve reached target pigmentation.

Frequently asked questions