Melanotan II Side Effects
Medically reviewed by Dr. Jonathan Snipes, MD
Reviewed for clinical accuracy · Last reviewed July 22, 2026 · Review policy
Quick answer
The most common Melanotan II side effects are nausea, facial flushing and darkening or change in moles and freckles, and are usually mild and dose-related. Serious effects are less common; the full breakdown and cautions are below.
| Effect | Frequency |
|---|---|
| NauseaEspecially after early doses | Common |
| Facial flushing | Common |
| Darkening or change in moles and frecklesBecause it stimulates pigment cells; new or changing moles warrant a skin check | Common |
| Prolonged erections (priapism)A medical emergency if an erection lasts several hours | Less common |
| Decreased appetite, spontaneous erections | Reported |
Melanotan II's side effects are a real part of why it is discouraged. Nausea and flushing are common early on. Because it drives pigment production, it commonly darkens moles and freckles and can cause new ones, which is a specific concern given the importance of monitoring moles for skin cancer. Prolonged, painful erections (priapism) are a recognized risk and a medical emergency. These issues, combined with unregulated supply, are why health authorities warn against it.
Frequently asked questions
What are the most common Melanotan II side effects?+
The most common Melanotan II side effects are nausea, facial flushing and darkening or change in moles and freckles. See the full frequency table above for less common and rare effects.
Is Melanotan II safe?+
Melanotan II's human safety is not well characterized because it has not completed formal human safety trials. Any use should be through a licensed clinician and a legitimate pharmacy, not research-chemical suppliers.