Melanotan II is not approved by any comparable regulator, so there is no label, no adverse-reaction table, and no post-marketing surveillance system. This page summarises what the published literature records. It is not medical advice.
Overview
Most safety pages on this site can quote frequencies. This one cannot, because frequency requires a denominator and nobody knows how many people use Melanotan II or what they inject. What exists instead is a set of published case reports in which clinicians describe patients arriving in emergency departments and dermatology clinics after using it. Case reports cannot establish causation or incidence — but when they are the entire literature for a use, their contents are the most specific safety information available.
The reported harms cluster in three places, all of them predictable from non-selective melanocortin activation: sympathomimetic and muscular toxicity, urological emergencies, and the pigment system.
The predictable effects, from the one trial
The 1998 crossover study in ten men reported transient nausea, yawning and stretching, and decreased appetite more frequently after Melanotan II than after placebo, at 0.025 mg/kg — none severe enough to require treatment (Wessells et al., J Urol 1998). Facial flushing and warmth are reported alongside these in the wider literature.
The value of that list is that it comes from a controlled setting: these are not user anecdotes but effects observed against a placebo arm at a pharmacologically active dose. Nausea in particular is not a sign of a bad batch — it is what a central melanocortin agonist does. For comparison, the refined successor bremelanotide produced nausea in 40% of women in its phase 3 programme versus 1.3% on placebo (Vyleesi label, DailyMed).
Documented acute emergencies
Systemic toxicity and rhabdomyolysis. A 39-year-old man injected 6 mg of internet-purchased Melanotan II — six times the starting dose he reported having been advised to use — and presented two hours later with diaphoresis, mydriasis, tremor, and a heart rate peaking at 146 bpm. His creatine phosphokinase rose from 1,760 to 17,773 IU/L over 12 hours with creatinine of 2.25 mg/dL; he spent three days in intensive care on fluids and bicarbonate. Mass spectrometry confirmed the injected substance was Melanotan II (Nelson et al., Clin Toxicol 2012).
Ischemic priapism requiring surgery. A patient presented with acute ischemic priapism after subcutaneous Melanotan II. Cavernosal aspiration, irrigation, and intracavernous phenylephrine all failed to achieve detumescence, and he required operative penoscrotal decompression (Mallory et al., Sex Med 2021). Ischemic priapism is a time-critical emergency: prolonged episodes can cause permanent erectile tissue damage. The authors note it had been reported after Melanotan II only twice before.
Renal infarction. A nephrology case report and literature review attributes a renal infarction to Melanotan II, noting prior reports of rhabdomyolysis and renal failure, and raising both thrombotic and direct toxic mechanisms (Peters et al., CEN Case Rep 2020).
Two features recur across these reports. The events were acute rather than cumulative, and in the rhabdomyolysis case the trigger was a dosing error that the format invites — a hand-reconstituted vial and a syringe, with no verified concentration.
The pigmentary risk, and why it is structural
Melanotan II darkens skin by stimulating melanocytes, the cell type from which melanoma arises. Published reports document melanoma in situ associated with melanotan use (Ong and Bowling 2012) and multiple new atypical melanocytic naevi appearing after two injections (Reid et al. 2013). A 2017 review of unregulated α-MSH analogue use counts four case reports of melanoma arising from existing moles during or shortly after melanotan use, while stating that causation is not established (Habbema et al., Int J Dermatol 2017).
The structural point is what happens to detection. Darkening pre-existing moles changes the visual cues clinicians use to catch melanoma early. The approved drug in this class handles that by requiring a full-body skin examination twice a year; unsupervised use of a related peptide removes the monitoring while keeping the effect. Any new, changing, or darkening lesion warrants prompt dermatological assessment.
What is missing from this picture
Everything a safety profile normally contains. There are no long-term human studies, no defined contraindications, no interaction data, no cardiovascular monitoring programme, and no way to know what is in a given vial — the rhabdomyolysis case is notable partly because it is one of the few in which the injected material was chemically confirmed. Products sold under the melanotan name include nasal sprays and blends with other peptides, none characterised.
Absence of reported harm in an unregulated market is not evidence of safety; it is the expected result of having no surveillance system. Broader context on this category is in what are the risks of peptides.