Possible Side Effects of Melanotan 2

Melanotan 2, commonly shortened to MT2, interacts with melanocortin receptors involved in pigmentation and other physiological processes. Limited human studies and medical case reports describe several effects, but reliable information about their frequency and long-term significance remains limited.

For a broader overview of the terminology, reported effects and current UK regulatory position, read our guide to tanning injections in the UK.

What Do We Know About Melanotan 2 Side Effects?

Melanotan 2 has not completed the type of large, modern clinical-development programme normally required for an authorised medicine. Much of the available human evidence comes from small early studies, individual medical case reports and reports from people who say they have used products sold as Melanotan 2. These forms of evidence are not equally reliable:

• Controlled studies can record effects under defined research conditions, but the available MT2 studies involved very small numbers of participants.
• Case reports can identify possible serious reactions, but they cannot show how frequently an event occurs or prove causation by themselves.
• User reports may describe genuine experiences, but product identity, amount, purity, other substances used and relevant medical history are often unknown.

It would therefore be inaccurate to present every reported symptom as a proven effect. It would also be inaccurate to claim that an incompletely studied product is free from risk. For broader background, read our guide explaining what Melanotan 2 is and what human research has studied.

Changes in Skin Pigmentation

The principal effect associated with Melanotan 2 is increased pigmentation. Melanotan 2 interacts with melanocortin receptors, including signalling pathways involved in melanin production. Melanin is produced by cells called melanocytes and contributes to the colour of the skin, hair and eyes. An early pilot phase I study published in 1996 involved three healthy male volunteers. Increased pigmentation was measured in two participants following Melanotan 2 administration under study conditions.^[1] This study provides evidence that Melanotan 2 can affect human pigmentation. However, three participants are not enough to determine how consistently this happens across the wider population or establish its long-term safety. Pigmentation may not appear uniform. Existing freckles, moles and areas of pigmentation may become darker or more noticeable.

Nausea

Nausea is one of the more consistently documented short-term effects in the limited human studies. The 1996 pilot study recorded mild nausea at several of the investigated levels. A later double-blind crossover study involving ten men also reported nausea more frequently following Melanotan 2 than placebo.^[1][2] These studies were small and used Melanotan 2 under research conditions. They cannot establish how frequently nausea occurs with products obtained outside a clinical study. Persistent vomiting can cause dehydration. Anyone who cannot keep fluids down, becomes confused, produces very little urine or develops other concerning symptoms should seek medical advice.

Facial Flushing

Facial flushing was reported during the early phase I study. This may appear as temporary redness or a sensation of warmth affecting the face or upper body.^[1] Not every episode of flushing following the use of a product will necessarily have the same cause. Flushing accompanied by difficulty breathing, facial or throat swelling, chest pain, collapse or severe weakness requires urgent medical assessment.

Stretching, Yawning and Tiredness

Stretching and yawning were recorded in early human studies. Fatigue or sleepiness was also reported by some participants in the 1996 pilot study.^[1][2] These findings provide more direct evidence than anonymous online reports. However, the studies remain too small to determine how often these effects occur or identify everyone who may be more susceptible.

Changes in Appetite

Decreased appetite was reported more frequently following Melanotan 2 than placebo in a small controlled study involving ten men.^[2] This should not be interpreted as evidence that Melanotan 2 is a safe or authorised weight-management treatment. The study was not designed to assess sustained weight loss, nutritional effects or long-term weight management. Prolonged loss of appetite, unexplained weight loss or difficulty maintaining normal food and fluid intake should be discussed with a qualified healthcare professional.

Sexual Arousal and Erections

Melanotan 2 has produced erections and changes in sexual arousal in small human studies. In a 1998 double-blind, placebo-controlled crossover study involving ten men with psychogenic erectile dysfunction, clinically apparent erections occurred in eight participants following Melanotan 2. Nausea, stretching, yawning and decreased appetite were also reported more frequently than with placebo.^[2] This was a small experimental study. Melanotan 2 is not an authorised UK treatment for erectile dysfunction, and the findings should not be interpreted as general evidence of safety or suitability. Individual medical reports have also described priapism following the use of products identified as Melanotan 2. Priapism is a prolonged erection that can cause permanent injury if it is not treated promptly.^[3] The NHS advises calling 999 or attending A&E when an erection lasts longer than three to four hours.^[4] Further information is available in our article about Melanotan 2, sexual arousal and erectile-dysfunction research.

Headaches and Dizziness

Headaches and dizziness are discussed in user reports and medical summaries, but they are less clearly characterised in the small controlled MT2 studies than effects such as nausea, flushing, yawning and erections. A headache or episode of dizziness occurring after use does not by itself prove that Melanotan 2 was responsible. Dehydration, heat, reduced food intake, UV exposure, another substance or an unrelated medical condition may also contribute. Severe or sudden headache, fainting, confusion, weakness affecting one side of the body, difficulty speaking or persistent dizziness requires urgent medical assessment.

Darkening of Freckles and Moles

Medical publications have described darkening of existing moles and the appearance of new or changing melanocytic lesions in association with unregulated melanotan use. A medical review published in 2017 identified case reports involving changes in existing moles, newly emerging atypical moles and melanomas that appeared during or shortly after melanotan use.^[5] The authors stated that conclusive evidence linking melanotan use to melanoma was lacking. A collection of case reports cannot prove that Melanotan 2 caused the reported cancers, particularly when UV exposure and other individual risk factors may also be involved. However, this uncertainty does not mean that changing moles should be ignored. NHS guidance recommends checking for:

• A new mole, growth or lump
• A mole or freckle that changes in size, shape or colour
• A patch of skin that changes noticeably
• A lesion that bleeds, itches, becomes painful or does not heal

New or changing lesions should be assessed by a qualified healthcare professional. Our separate guide examines pigmentation and whether reported Melanotan 2 effects are reversible.

Serious Reactions Described in Case Reports

Medical literature contains individual reports of more serious events occurring after the use of products identified as Melanotan 2. Published examples include:

• Priapism requiring hospital treatment
• Systemic toxicity
• Rhabdomyolysis, which involves the breakdown of muscle tissue
• Kidney dysfunction occurring alongside systemic toxicity

A 2012 report described systemic symptoms, rhabdomyolysis and renal dysfunction following Melanotan 2 use.^[6] This was an individual case and cannot establish the frequency of such events. Factors including the amount used, product composition, contamination, other substances and the patient’s health may be relevant. Nevertheless, serious case reports identify possible risks that should not be omitted or presented as routine minor effects.

What Has the MHRA Reported?

An MHRA Freedom of Information response published in April 2024 recorded 16 UK spontaneous suspected adverse-drug-reaction reports involving Melanotan II between 1 January 2012 and 31 December 2022.^[7] The MHRA explains that a suspected-reaction report does not prove that the product caused the event. Reporting is also incomplete and variable, so the number of reports cannot be used to calculate how many people experience side effects. The figures should therefore be treated as safety-reporting data, not as a reliable estimate of risk or prevalence.

Injection-Related Risks

Injecting any substance introduces risks that are separate from the pharmacological effects of the substance itself. These may include:

• Pain, redness or irritation at the injection site
• Bleeding or bruising
• Local infection
• Contamination caused by poor handling
• Transmission of blood-borne infections when equipment is shared
• Uncertainty about sterility

Spreading redness, increasing pain, significant swelling, discharge, fever or feeling seriously unwell should be medically assessed. This article does not provide injection instructions or personalised medical guidance.

What About Nasal Products?

A nasal product does not involve an injection, so it does not carry injection-site or shared-needle risks. That does not establish that nasal administration is clinically tested, predictable or risk-free. The principal human studies cited on this page investigated Melanotan 2 through subcutaneous administration. Their findings cannot automatically be applied to nasal products or used to establish how much of a nasal product is absorbed. The response to a nasal product may be affected by its formulation, concentration, spray mechanism, storage, preparation and the condition of the nasal passages. Reliable human evidence establishing nasal absorption and dose equivalence remains limited.

Does Increased Pigmentation Protect Against UV Damage?

Visible pigmentation should not be treated as adequate protection against ultraviolet radiation. The NHS states that there is no safe or healthy way to obtain a UV tan and that a tan does not protect the skin from the sun’s harmful effects.^[8] There is insufficient evidence to claim that pigmentation associated with Melanotan 2 makes intentional UV exposure safe or provides a predictable sun-protection factor. UV exposure can still damage skin-cell DNA even when visible burning does not occur. A darker appearance should not replace sunscreen, protective clothing, shade or sensible limits on exposure to sunlight and sunbeds. Current NHS guidance recommends sunscreen with at least SPF 30 and at least four-star UVA protection, alongside shade and protective clothing.

Why Is the Frequency of Side Effects Unknown?

There are no large, high-quality clinical studies that allow reliable percentages to be assigned to most reported Melanotan 2 effects. Products obtained outside regulated pharmaceutical supply chains may also vary. When someone experiences a symptom, it may be difficult to determine:

• Whether the product contained the substance stated on its label
• How much of the substance was present
• Whether impurities or contaminants were present
• Whether another medicine or substance contributed
• Whether the symptom was related to an existing condition

Claims that a particular effect happens to a fixed percentage of all users should be treated cautiously unless they are supported by appropriate clinical evidence.

What Can Laboratory Testing Establish?

Independent laboratory analysis can provide information about the particular sample submitted for testing. Depending on the analysis, it may record identity, measured content and reported purity. The laboratory document currently published by Pure MT2 relates to sample order number 100011931. It identifies the submitted sample as Melanotan II, records measured content of 9.97mg and reports purity of 99%. These results relate only to that submitted sample. The report does not establish:

• Clinical safety or effectiveness
• Sterility or suitability for human use
• The likelihood of side effects
• Nasal absorption or delivery
• Regulatory approval
• The composition of another sample or future batch

View the complete laboratory report and explanation of its findings.

What Is the UK Regulatory Position?

Melanotan 2 is not authorised in the United Kingdom as a medicine for cosmetic tanning. In a December 2025 parliamentary answer, the Department of Health and Social Care stated that Melanotan II injections and pens are considered medicinal products. Medicinal products require the relevant marketing authorisation to be legally sold and supplied in the United Kingdom.^[9] The same answer stated that tan-enhancing nasal products marketed clearly for cosmetic self-tanning, without a medical purpose, do not fall within medicines regulations or the MHRA’s remit.^[9] Regulatory classification can therefore depend on product format, presentation and the claims used to market it.

When Should Medical Help Be Sought?

Anyone experiencing severe, persistent or unusual symptoms should seek advice from a qualified healthcare professional. Call 999 or attend A&E for symptoms such as:

• Difficulty breathing or significant facial or throat swelling
• Collapse, severe confusion or loss of consciousness
• Chest pain
• An erection lasting longer than three to four hours
• Severe muscle pain or weakness accompanied by dark urine
• Sudden weakness, difficulty speaking or another possible neurological emergency

Contact a GP about a new or changing mole, persistent vomiting, unexplained weight loss, signs of infection or any symptom that continues or worsens. Suspected adverse reactions can also be reported through the MHRA Yellow Card scheme.^[10]

Summary

The short-term effects most clearly documented in the limited human studies include nausea, facial flushing, stretching, yawning, fatigue, decreased appetite and erections. Increased pigmentation was measured in two of the three participants in the early pigmentation study. Medical case reports have described more serious events, including priapism, systemic toxicity and rhabdomyolysis. These reports identify possible safety signals but cannot show how frequently the events occur or prove that every event was caused solely by Melanotan 2. Changes involving freckles and moles have also been reported. The available evidence does not establish that Melanotan 2 causes melanoma, but new or changing skin lesions should still be medically assessed. The absence of large clinical studies means the complete safety profile, long-term effects and frequency of adverse reactions remain uncertain. In the United Kingdom, Melanotan II injections and pens are treated as medicinal products, while cosmetic tan-enhancing nasal products presented without a medical purpose are treated differently under the current position described by the Department of Health and Social Care.

Sources and Further Reading

1. Dorr RT, Lines R, Levine N, et al. Evaluation of Melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study. Life Sciences. 1996;58(20):1777-1784.
2. Wessells H, Fuciarelli K, Hansen J, et al. Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo-controlled crossover study. Journal of Urology. 1998;160(2):389-393.
3. Dreyer BA, Amer T, Fraser M. Melanotan-induced priapism: a hard-earned tan. BMJ Case Reports. 2019.
4. NHS. Priapism, painful erections.
5. Habbema L, Halk AB, Neumann M, Bergman W. Risks of unregulated use of alpha-melanocyte-stimulating hormone analogues: a review. International Journal of Dermatology. 2017;56(10):975-980.
6. Nelson ME, Bryant SM, Aks SE. Melanotan II injection resulting in systemic toxicity and rhabdomyolysis. Clinical Toxicology. 2012;50(10):1169-1173.
7. Medicines and Healthcare products Regulatory Agency. Side effects reports of Melanotan II products, FOI 24/274. 17 April 2024.
8. NHS. Sunscreen and sun safety.
9. UK Parliament, Department of Health and Social Care. Legal status of products containing Melanotan II. Answered 15 December 2025.
10. Medicines and Healthcare products Regulatory Agency. Yellow Card reporting scheme.

Last evidence review: 22 September 2026