Melanotan II: Tanning, Libido, and Appetite — Complete Guide

Written by Adam Maggio | Medically reviewed by Dr. Sarah Chen, PharmD, BCPS

Melanotan II is a synthetic melanocortin peptide that stimulates melanin production (tanning), increases libido, and suppresses appetite. Typical dose: 0.5–1 mg subcutaneously. Side effects include nausea, facial flushing, and spontaneous erections. Requires UV exposure for tanning effect.

What Is Melanotan II?

Melanotan II (MT2) is a synthetic analogue of alpha-melanocyte stimulating hormone (alpha-MSH), a naturally occurring peptide that regulates skin pigmentation, sexual function, appetite, and inflammation. Developed at the University of Arizona in the 1980s as part of a research program to develop a sunless tanning agent, MT2 has since attracted interest for its diverse effects on multiple physiological systems.

Mechanism of Action

MT2 is a non-selective melanocortin receptor agonist, binding to MC1R (melanocyte receptor — drives tanning), MC3R (energy homeostasis — reduces appetite), MC4R (sexual function — increases libido), and MC5R (exocrine gland function). This broad receptor binding profile explains MT2's diverse effects.

Tanning Effects

MT2 stimulates melanocytes in the skin to produce and distribute melanin. Importantly, MT2 requires UV exposure to produce a tan — it amplifies the skin's response to UV radiation rather than producing pigmentation independently. Even minimal sun exposure (15–20 minutes daily) produces a significantly deeper tan with MT2. The tanning effect typically begins after 1–2 weeks of use and can persist for several weeks after discontinuation.

Libido Enhancement

MT2's activation of MC4R receptors in the hypothalamus and limbic system produces significant pro-sexual effects, including increased libido, spontaneous erections in men, and enhanced arousal in women. This effect was so pronounced in early clinical trials that it led to the development of PT-141 (bremelanotide) — a closely related peptide specifically developed for sexual dysfunction.

Dosing Protocol

Typical research protocols use 0.25–1 mg subcutaneously, administered in the evening. A common approach is to start with a loading dose of 0.25–0.5 mg daily for 1–2 weeks to build up melanin, then transition to a maintenance dose of 0.5–1 mg 2–3 times per week.

Side Effects

The most common side effects include nausea, facial flushing, yawning, and spontaneous erections in men. Nausea can be minimized by starting with low doses, injecting in the evening, and taking an antihistamine 30 minutes before injection. Moles and freckles may darken with MT2 use.