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Melanotan II

Last reviewed: April 18, 2026 by The Peptide Catalog Team

A fast-acting peptide for tanning, libido enhancement, and appetite control. Melanotan II is a synthetic peptide that stimulates melanin production (tanning) and has effects on sexual function and appetite. More potent than Melanotan I with additional effects on libido. Not FDA-approved; used in research settings.

CategoryTanning Peptides
Classmelanocortin agonist
GoalSkin & HairSexual Health
Overview

Core Benefits

Key Advantages
Rapid tanning effect
Visible skin darkening in 1–2 weeks of dosing.
Libido side benefit
MC3R/MC4R activation increases sexual desire (basis for PT-141).
Appetite suppression
MC4R activation reduces hunger during loading phase.
Tans fair skin
Overrides MC1R variants that normally resist tanning.
Real side-effect risks
Nausea, flushing, and mole darkening are real risks.
Maintenance dosing
After loading, 1–2 doses per week sustain the tan.

These are educational summaries of commonly discussed effects in wellness/regenerative contexts, not guarantees.

Melanotan II Results Timeline

Progression
1
Day 1–3
Physical Changes
Facial flushing, nausea common; spontaneous erections possible
Performance & Recovery
Libido increase may begin
Other Benefits
Appetite suppression noticeable; start with low dose (0.1mg)
2
Week 1–2
Physical Changes
Freckles/moles darken; early tan visible with UV exposure
Performance & Recovery
Increased libido/sexual response
Other Benefits
Side effects typically diminish; appetite remains reduced
3
Week 2–3
Physical Changes
Noticeable tan developing rapidly
Performance & Recovery
Sustained libido effects
Other Benefits
Loading phase complete for most users
4
Week 3+
Physical Changes
Full tan achieved; deeper than MT-I
Performance & Recovery
Libido effects persist with dosing
Other Benefits
Maintenance: 1–2 doses/week maintains tan

Timeline is illustrative and non-guaranteed. Outcomes vary and are commonly discussed alongside training, nutrition, sleep, and cycling practices.

Read the full Melanotan II results timeline →

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Evidence at a glance

Two parallel grades per outcome — clinical RCT depth and real-world community adoption. See the Research Overview below for citations and detail.

OutcomeClinical EvidenceCommunity Evidence
Erectile function in EDModerateModerate
Female sexual desire / arousalWeakModerate
Cosmetic tanningWeakModerate
Long-term safety / melanoma signalWeakModerate
How It WorksMelanocortin Agonist — Non-Selective (MC1R/MC3R/MC4R)

Receptor → Multi-Receptor Signal → Tanning & Libido → Outcomes

1
Target

MC1R + MC3R + MC4R (Multiple Melanocortin Receptors)

Melanotan-2 activates multiple melanocortin receptors: MC1R (tanning), MC3R/MC4R (sexual function, appetite). This broad activation produces potent tanning but also causes significant off-target effects that Melanotan-1 avoids.

2
Cellular Signal

Multi-Receptor cAMP → Melanin + Central Effects

MC1R activation drives melanin production (same as MT-1). MC3R/MC4R activation in the brain produces sexual arousal effects (similar to PT-141, which was derived from MT-2) and appetite modulation. Nausea is common from central melanocortin activation.

3
Systemic Effect

Rapid Tanning + Libido Effects + Appetite Suppression

Faster and more dramatic tanning than Melanotan-1. Significant libido increase. Moderate appetite suppression. Possible nausea, especially at higher doses or during loading. The multi-receptor profile creates a broader but less controllable effect.

4
What You Notice

Fast Tanning + Flushing + Libido Increase

Facial flushing within hours of first doses. Tanning visible within 1-2 weeks. Libido increase is common and sometimes pronounced. Nausea at higher doses. More dramatic results but more side effects than Melanotan-1.

What Makes This Peptide Different

Melanotan-2 is the more potent but less selective melanocortin. It produces faster, darker tanning than MT-1 but with significant off-target effects (libido, nausea, appetite changes). PT-141 (Bremelanotide) was actually derived from MT-2 research — isolating the sexual function effects via MC3R/MC4R selectivity.

Research overview

Outcome-by-outcome look at what the evidence actually supports for Melanotan II, including human vs. animal study counts and our editorial take on each.

Erectile function in men

Clinical:ModerateCommunity:Moderate

Wessells 2000 (n=20) randomized men with erectile dysfunction to MT-II or placebo in crossover design and showed penile erection in 17/20 men in the absence of stimulation, with 68% reporting increased sexual desire vs 19% on placebo. Subsequent work led to development of bremelanotide (PT-141), a closely related analog, while MT-II itself was abandoned for clinical use due to off-target tanning, nausea, and melanocytic effects.

2 human studies · 8 animal studies

Key findings & citations
  • Wessells 2000: erection in 17/20 men with ED on MT-II vs minimal on placebo.
  • Sexual desire increased 68% vs 19% placebo.
  • Severe nausea in ~13% at 0.025 mg/kg — meaningful tolerability cost.
  • Bremelanotide (PT-141) replaced MT-II in clinical development.

Our take

Real pro-erectile effect, dirty side-effect profile. PT-141 is the cleaner version of the same idea.

Cosmetic tanning and melanocytic risk

Clinical:WeakCommunity:Moderate

MT-II tans skin via MC1R agonism, but case reports document new and changing melanocytic nevi in users. The mechanism (melanocyte stimulation) is biologically the wrong direction for melanoma risk. No prospective long-term safety study has been completed in cosmetic users.

0 human studies · 4 animal studies

Key findings & citations
  • Reliable pigmentation effect via eumelanin synthesis.
  • Multiple dermatology case reports of new/changing nevi during MT-II use.
  • No long-term cosmetic-user safety trial — risk-benefit is essentially anecdotal.

Our take

It works for tanning. The cancer-relevant mechanism is exactly backward — we'd recommend afamelanotide (MT-1) over MT-II if pigmentation is the goal.

What Melanotan II doesn't do

Claims that current evidence does not support. Worth knowing before you set expectations.

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Dosing ProtocolTanning

Educational reference only. Individual responses vary. Consult healthcare provider before use.

Vial Size
10 mg
Reconstitution
2 ml BAC water
Dose
250-500 mcg (5-10 units)
Timing
AM
Frequency
Daily during loading, then 1-2x/week
Duration
Loading: 2-3 weeks, then maintain
Protocol Notes
More potent than MT-I but more side effects (nausea, flushing, libido effects). Start with 100mcg to assess tolerance.

Why This Dosing Protocol

Why start at 100 mcg? MT-2 commonly causes nausea, especially initially. Starting at 100mcg and working up to 250-500mcg helps assess tolerance.

Why loading + maintenance? Same melanin-building logic as MT-1. Daily loading for 2-3 weeks, then 1-2x/week to maintain. MT-2 achieves results faster due to stronger melanocyte stimulation.
Full Dosing GuideReconstitution CalculatorCycle Cost Calculator

Reconstitution Calculator

Dilution math and unit conversions. Prefilled using a common vial size for this peptide.

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Storage & Handling

Storage at a glance

Proper storage temperatures, shelf life, reconstitution best practices, and travel tips for lyophilized and reconstituted peptides.

Powder: Freezer
1+ year at -20°C
Reconstituted: Fridge
4 weeks max at 2-8°C
View Complete Storage Guide

Handling specifics

Educational overview on storage, labeling, and traceability considerations for lab environments. Consult primary literature and vendor documentation for specifics.

Powder storage (very stable)
  • Freezer (-20°C): 1+ year
  • Refrigerator (2-8°C): 1-3 months
  • Room temperature: 2-3 weeks (emergency only)
Reconstituted storage (fragile)
  • MUST refrigerate at 2-8°C
  • 4-week maximum shelf life
  • NEVER freeze after reconstitution
  • Use bacteriostatic water for multi-dose
Molecular Structure

Melanotan II sequence

Click any residue to see its properties.

HydrophobicPolarAcidic (−)Basic (+)Special

Sequence-derived properties

Length
5 residues
Molecular weight
772.9 Da
backbone only
Avg hydrophobicity
-1.94
Kyte–Doolittle scale

Residue classes

Hydrophobic: 2 (40%)Basic (+): 3 (60%)

Net charge distribution

Positive3 (60%)
Neutral2 (40%)
Negative0 (0%)

Amino acid frequency

F×1H×1K×1R×1W×1

Modifications

  • Cyclic lactam bridge between Asp and Lys
  • D-Phe at position 7

Sequence and properties provided for educational reference. Not for clinical dosing decisions.

  • Length: 7 amino acids
    (Cyclic structure.)
  • Origin: α-MSH analog
    (Synthetic melanocortin receptor agonist.)
  • FDA Status: Not approved
    (Research use only.)
  • Primary Use: Melanin stimulation
    (Tanning + additional MC receptor effects.)
Peptide sequence
Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂
The cyclic structure provides broader melanocortin receptor activation, affecting MC1R (tanning), MC3R/MC4R (sexual function, appetite).
Key takeaway: Melanotan II is more potent for tanning but has additional effects on libido and appetite. Not FDA-approved and has more side effects than Melanotan I.

FAQ

What are Melanotan II's effects beyond tanning?

Beyond stimulating melanin production (tanning), Melanotan II has effects on sexual function (may increase libido and cause erections) and can reduce appetite. These additional effects are due to its action on melanocortin receptors throughout the body, not just in skin cells.

What are the two types of melanin and which does Melanotan-2 stimulate?

Humans produce two types: eumelanin (brown/black, protective) and pheomelanin (red/yellow, potentially harmful). Melanotan-2 activates MC1R receptors to increase eumelanin synthesis. This matters because eumelanin absorbs UV radiation and dissipates it as heat, while pheomelanin generates DNA-damaging free radicals when exposed to UV. The tan from Melanotan-2 is genuine eumelanin-based protection.

Why do redheads burn instead of tan?

Red hair is caused by MC1R gene variants that shift melanin production toward pheomelanin instead of eumelanin. Pheomelanin provides almost no UV protection and actually generates free radicals in sunlight. This is why redheads burn easily and have higher melanoma rates. Melanotan-2 can partially override these MC1R variants, allowing eumelanin production even in people who normally can't tan.

How is Melanotan-2 different from Melanotan-1?

Melanotan-2 is cyclic (ring structure) vs Melanotan-1's linear form, making it more potent but less selective. MT-2 activates MC1R (tanning), MC3R, MC4R, and MC5R. This broader activity causes its sexual effects (erections, libido via MC3R/MC4R) and appetite suppression. Melanotan-1 is more selective for MC1R, so it mainly just tans without the sexual/appetite effects. MT-1 is FDA-approved; MT-2 is not.

What are the side effects of Melanotan-2?

Common: nausea, facial flushing, fatigue, spontaneous erections, increased libido, decreased appetite. Moles and freckles may darken (monitor for changes). More concerning: some reports of new mole development or changes to existing moles — any suspicious changes should be evaluated by a dermatologist. It's not FDA-approved and long-term safety is not established.

How long does reconstituted peptide last?

Once mixed with bacteriostatic water, peptides remain stable for up to 4 weeks when refrigerated at 2-8°C (36-46°F). Unopened powder can last 1+ year in the freezer. Get our complete Storage & Travel Guide.

Is this peptide legal to purchase?

Peptides sold "for research purposes only" are legal to purchase in the US, but are not FDA-approved for human use outside of specific medical applications. Always consult a healthcare provider before use.

New to peptides?

Take our Peptide Match tool to find the best peptide for your goals. You can also read our Complete Guide to Peptides to learn the basics.

Scientific Sources

The following peer-reviewed studies and official resources provide additional scientific context for this peptide:

Melanotan II Research Articles

guides

Melanotan-2 Dosage: 100mcg → 500mcg Loading Chart

Loading schedule by skin type, maintenance dose timing, SubQ vs nasal comparison, and the dose escalation most people get wrong.

comparison

PT-141 vs Melanotan 2: Key Differences

PT-141 is FDA-approved for sexual function, MT-2 is not — but MT-2 adds tanning. Side-by-side on effects, safety, and cost.

side-effects

Melanotan 2 Side Effects: 8 to Watch For

Nausea hits most users on day 1 — but mole changes are the one to actually worry about. Full safety breakdown with what's normal vs when to stop.

results

Melanotan-2 Results: Visible Tan in 2-3 Weeks

Visible change reported at 2-3 weeks after a 5-10 day load, though Fitzpatrick type I runs longer. Plus how long the tan holds after stopping.

Compare Melanotan II to alternatives

Side-by-side mechanism, dose, half-life, and vendor pricing.

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Disclosure: we may earn affiliate commission from qualifying purchases. Educational information only — not medical advice.