Human and animal studies
Melanotan 2 Research found several effects but little human proof
You can see how skin, hunger, and erections changed in each study.
Most findings came from animals, not people
Nausea or darker skin is something you can notice yourself. The Melanotan 2 studies also asked what caused those changes. Skin work looked at how cells made more brown color. Brain work asked why hunger and sexual function changed. Most brain studies used animals, not people.
Each section tells you if people or animals took part. An amount tells you only what one study used. It doesn't tell you what to take. No authority has approved Melanotan 2 for use in people [3]. Keep that limit with you as you read.
The first small human study found darker skin
The earliest Melanotan 2 human study asked whether skin could darken without sunlight. It enrolled 3 healthy men, who received Melanotan 2 shots under the skin on every other weekday. The amount began at 0.01 milligrams for each kilogram the man weighed. Over two weeks, it rose to 0.025-0.03 milligrams for each kilogram. Skin on the face, chest, back, and buttocks darkened in 2 of 3 men. Without a sunlamp, doctors could measure darker color once five low shots had been given [1]. These amounts aren't an approved dose or advice for you.
Melanotan 2 makes skin cells produce more dark brown pigment. Sunlight begins the pigment work by another route. In a rat study, 4.6% of the swallowed amount reached the blood [7]. That small share helps explain why the early work used shots.
Melanotan 2 tanning came with nausea and erections
The small tanning study found more than darker skin. Men also had mild nausea and erections lasting 1-5 hours [1]. You can't separate those effects once the compound is in your body.
Later tanning reports described darker moles, new moles, and melanoma. You can review them on the Melanotan 2 effects page [16]. A historical review also followed two related compounds. One related medicine later gained approval for a rare illness triggered by sun. The other became a drug for sexual problems [3]. Melanotan 2 itself remained unapproved.
Mice and rats ate less after the compound
One study tested Melanotan 2 in a part of the mouse brain involved in reward. Researchers placed a measured lab amount on both sides of that area. Afterward, the mice ate smaller amounts and stopped sooner while working for food [5]. A bad taste didn't explain the change. The way their bodies used energy didn't change. Melanotan 2 reduced both the wish for food and the amount eaten.
A rat study also found less eating and less fat gain [10]. Melanotan 2 didn't reverse changes in sex hormones or growth hormone. Growth hormone helps manage growth, muscle, and fat. Another rat study compared several diets. Melanotan 2 had its largest effect in rats eating more hard animal fat [44]. Those rats mainly chose less fat. None of this proves weight loss for you.
A small study found longer erections in men
Researchers noticed erections by chance, then studied them in 10 men. At different times, each man received Melanotan 2 and a placebo. A placebo contains no medicine. The amount was 0.025 milligrams for each kilogram the man weighed, given under the skin. Clear erections occurred in 8 of 10 men. The penis tip stayed more than 80% firm for an average of 38.0 minutes. After placebo, the average fell to 3.0 minutes. The gap was too large to look like chance alone. Nausea, stretching, and yawning were brief and needed no care [2].
A later review concluded that the erection effect starts in the brain [8]. Melanotan 2 changes brain activity tied to erections and interest in sex. It doesn't begin by widening blood vessels, as some erection drugs do. This difference may help explain why erections, yawning, and hunger changed together.
In rats, the compound stirred a second brain hormone
A rat study put Melanotan 2 into a vein. The rat's oxytocin-making brain cells then became more active [9]. Oxytocin is a hormone involved in touch, birth, and social bonds. This brain response may help explain stretching, yawning, and sexual effects. Men had stretching and yawning in the small Melanotan 2 erection study too [2]. The rat finding doesn't tell you that the same chain happened in those men.
The human proof remains small and early
The Melanotan 2 human studies included only 3 to 20 people. They examined darker skin [1] and erection trouble [2]. No larger follow-up trial was finished to test the compound in more people. Melanotan 2 hasn't gained approval for any use [3].
Animal studies found less eating, more erections, and oxytocin changes more than once. They may explain what happens, but an animal isn't you. Medical reports in people also describe grave harm [4], [36]. The record shows early signs of effects, not good proof of safe use.