Melanotan 2 was built in a University of Arizona lab to give people a tan without the sun.
Its first human study delivered the tan. It also delivered something nobody planned for, and that side effect went on to become a separate drug.
If you’re here for the numbers, you’ll get them: the doses the human studies actually used, how to mix a vial, and a calculator that turns any dose into units on your syringe. You’ll also get the part most dosage pages skip, which is what MT-2 does to your moles.
Melanotan 2 at a Glance
| Melanotan 2 (MT-2) | |
|---|---|
| What it is | A synthetic, ring-shaped peptide of 7 amino acids, modeled on the tanning hormone alpha-MSH |
| Main target | MC1R, the receptor on pigment cells that switches on melanin |
| Other targets | MC3R, MC4R and MC5R, which is why it also affects appetite and erections |
| Doses used in human studies | 0.01 to 0.03 mg/kg, injected under the skin |
| Where the tan shows first | Face and upper body |
| Most common side effects | Nausea, flushing, yawning and stretching, lower appetite, spontaneous erections |
| The one to watch | New or changing moles |
What Is Melanotan 2?
Your skin already makes its own tanning signal. It’s a hormone called alpha-melanocyte-stimulating hormone, or alpha-MSH, and it’s 13 amino acids long.
In the 1980s and 90s, researchers at the University of Arizona set out to build longer-lasting, more potent versions of it. They made two:
- Melanotan 1 (MT-1): a straight-chain version, developed for tanning.
- Melanotan 2 (MT-2): a shorter, ring-shaped version that’s far more potent and hits more receptor types.
MT-1 later became afamelanotide, a medicine for a rare light-sensitivity disorder. MT-2 went a different way. For the full head-to-head, see my breakdown of Melanotan 1 vs Melanotan 2.
How Melanotan 2 Darkens Your Skin
Pigment cells in your skin, called melanocytes, carry a receptor called MC1R. When MT-2 switches it on, those cells ramp up production of eumelanin, the dark brown pigment behind a tan.
In the first human study, the tan showed up on the face, upper body and buttocks. The buttocks rarely see the sun, which tells you MT-2 can push pigment without UV doing the work.
The Side Effect That Became a Drug
MT-2 also switches on MC4R in the brain, and in that first study, the volunteers got spontaneous erections lasting 1 to 5 hours.
Researchers followed that lead. MT-2 went on to be studied for erectile dysfunction, and a close relative developed from it, PT-141 (bremelanotide), became its own compound. I cover that one in my PT-141 dosage calculator guide.
Melanotan 2 Dosage: What the Human Studies Used
Three small human studies give us real dosing data. All of them used injections under the skin and dosed by body weight.
| Study | Who | Dose | What happened |
|---|---|---|---|
| First tanning study (1996) | 3 healthy men | Started at 0.01 mg/kg daily, raised in small steps to 0.025–0.03 mg/kg | Tan in 2 of 3 men. Mild nausea at most doses. Sleepiness and fatigue in 1 of 2 men at 0.03 mg/kg. Erections lasting 1 to 5 hours. |
| Erectile dysfunction trial (1998) | 10 men | 0.025 mg/kg | Erections in 8 of 10 men. Nausea, stretching, yawning and lower appetite were more common than with placebo. |
| Erectile dysfunction trial (2000) | 10 men | 0.025 mg/kg | Erections after 12 of 19 injections, versus 1 of 21 placebo shots. Severe nausea after 4 of 19 injections. |
The authors of the 1996 study picked 0.025 mg/kg as the dose for future trials.
To put that in milligrams: 0.025 mg/kg works out to about 1.75 mg for someone who weighs 70 kg (154 lb), and about 2.25 mg at 90 kg (198 lb).
The pattern across all three studies is clear: the side effects climbed with the dose. Nausea showed up at most dose levels, and at 0.025 mg/kg, about one injection in five caused severe nausea. That’s why people who use MT-2 tend to start with a small first dose and work up, rather than starting at a study dose.
Melanotan 2 Dosage Calculator
Here’s where most people get tripped up. The dose is in micrograms, the vial is in milligrams, and the syringe is in units.
Enter your vial size, how much water you added and the dose you’re working with. The calculator does the conversion and shows you exactly where to stop on the syringe.
Melanotan 2 Dose Calculator
Turn a dose in mcg into the exact number of units on your syringe.
Read the dose at the front edge of the black stopper, the side nearest the needle.
The math behind it is one formula:
Units to draw = (dose in mcg ÷ concentration in mcg per mL) × 100
Example: a 10 mg vial with 2 mL of water gives you 5 mg/mL, or 5,000 mcg per mL. A 250 mcg dose is 250 ÷ 5,000 = 0.05 mL, which is 5 units on a U-100 insulin syringe. That vial holds 40 of those doses.
Mixing Your Melanotan 2 Vial
MT-2 comes as a freeze-dried powder, so it needs to be mixed with water before you can measure a dose. Bacteriostatic water is the standard choice for a vial you’ll draw from more than once.
The volume of water doesn’t change how much peptide is in the vial. It only changes how much peptide sits in each unit. More water spreads the dose over more units, which makes small doses easier to measure.
For the full step-by-step, including how to add the water without blasting the powder and how long a mixed vial keeps, see my guide to reconstituting peptides.
How Fast Does Melanotan 2 Work?
Fast. In the clinical work, a visible tan appeared within about 5 doses.
In the 1996 study, two of the three men had measurably darker skin on the face, upper body and buttocks one week after their dosing ended. Researchers confirmed it with a skin reflectance meter, not just by eye.
Freckles and existing moles darken along with the rest of your skin, which brings us to the most important section in this article.
Melanotan 2 Side Effects
The Common Ones
These are the effects that show up in the studies and in user reports:
- Nausea: the most consistent one, and it scales with the dose.
- Facial flushing: a warm, red face shortly after a dose.
- Yawning and stretching: an odd but well-documented pattern that often comes before an erection.
- Lower appetite: from the same brain receptors that drive the erections.
- Spontaneous erections: lasting 1 to 5 hours in the first study.
- Fatigue and sleepiness: seen at the highest dose tested.
Moles: The One That Matters Most
MT-2 stimulates the pigment cells themselves, and that includes the ones in your moles.
Dermatologists have published a string of case reports on this:
- A 40-year-old man with a history of melanoma and many atypical moles developed new moles, and his existing ones darkened and grew. The changes reversed after he stopped.
- A 25-year-old man who used tanning beds developed more than 100 new moles, mostly on his back, a few weeks after a 4-week course. Doctors removed the 10 most worrying ones. All 10 were atypical, and 3 showed severe changes.
- A 20-year-old woman who used MT-2 for 3 to 4 weeks alongside sunbeds was diagnosed with melanoma on her buttock a few months later.
A 2017 review counted four case reports of melanoma arising from moles during or shortly after melanotan use. A causal link hasn’t been proven, but the pattern is consistent enough that dermatologists take it seriously.
Two details keep coming up in these cases: lots of moles to begin with, and sunbeds on top of the MT-2.
How to Keep an Eye on Your Moles
- Photograph your skin first: back, chest, arms and legs, so you have a baseline to compare against.
- Check monthly: look for new moles and for any mole that’s changing in size, shape or color.
- Know the warning signs: asymmetry, uneven borders, more than one color, a diameter bigger than a pencil eraser, or any mole that’s evolving.
- Get anything new or changing looked at: a dermatologist can check it with a dermatoscope in a few minutes.
If you have a personal or family history of melanoma, or a lot of moles already, you’re the group the case reports keep describing.
Rare but Serious Reactions
A small number of case reports describe much bigger problems:
- Priapism: an erection that won’t go down. In one case, it took drainage of the penis and a medication injection to resolve, and erectile function still hadn’t recovered four weeks later.
- Rhabdomyolysis: a breakdown of muscle tissue that can strain the kidneys, reported after an MT-2 injection along with an overstimulated, racing system.
- Kidney infarction: a 45-year-old man lost blood supply to about half of one kidney after injecting roughly 27 mg of MT-2 over six months.
For scale, Sweden’s poison information center logged 215 cases of MT-2 side effects between 2008 and 2019.
An erection lasting more than four hours is a medical emergency. Head to an emergency room, because the longer it goes, the higher the risk of permanent damage.
Where to Inject Melanotan 2
MT-2 goes under the skin, into the fat layer. The human studies all used subcutaneous injections.
The usual spots are the belly, about two inches out from the navel, and the front of the thigh. Rotate your sites so one patch of skin doesn’t take every dose.
A short insulin syringe does the job. My reconstitution guide covers syringe sizes, needle gauges and why every dose gets a fresh syringe.
What About Melanotan 2 Nasal Spray?
Nasal tanning sprays have taken off on social media. The spray is absorbed through the lining of the nose, and dermatologists report the same side effects as the injectable.
The catch is precision. How much reaches your bloodstream depends on the concentration in the bottle and how much each pump delivers, so you can’t measure a spray dose the way you can a syringe dose.
Quality Matters
MT-2 sold online varies widely in quality, and contamination has been flagged as a real risk. Check the batch’s certificate of analysis for identity and purity before you mix anything.
I go through what a good COA looks like in my guide on how to judge a supplier.
Bottom Line
Melanotan 2 is one of the most potent tanning compounds ever made. A visible tan can show up within a handful of doses, and it builds even on skin the sun never touches.
The human studies used 0.01 to 0.03 mg/kg, and the side effects rose right along with the dose. The calculator above turns whatever dose you’re working with into exact units on your syringe.
The part that deserves real attention is your skin. Map your moles before you start, keep checking them, and get anything new or changing looked at.
Frequently Asked Questions About Melanotan 2 Dosage
What dose of Melanotan 2 did the studies use?
The human studies used 0.01 to 0.03 mg/kg, injected under the skin. The first tanning study started at 0.01 mg/kg and its authors picked 0.025 mg/kg for future trials. Side effects, especially nausea, increased with the dose.
How many units of Melanotan 2 is 250 mcg?
It depends on how much water is in the vial. With a 10 mg vial and 2 mL of water, the concentration is 5,000 mcg per mL, so 250 mcg is 0.05 mL, or 5 units on a U-100 insulin syringe. With 1 mL of water, the same dose is 2.5 units.
How much bacteriostatic water do I add to a 10 mg vial of Melanotan 2?
Any volume works as long as you know what it is. Two mL is a common choice because it gives 5 mg/mL, which keeps the syringe math simple. More water makes each unit weaker and small doses easier to measure.
How long does Melanotan 2 take to work?
A visible tan appeared within about 5 doses in the clinical work. In the 1996 study, darker skin was measurable one week after dosing ended.
Does Melanotan 2 work without the sun?
Yes. In the first human study, pigment increased on the buttocks, which rarely see sunlight. Many users still pair it with sun or sunbeds, and sunbeds show up repeatedly in the melanoma case reports.
Does Melanotan 2 affect moles?
Yes. Case reports describe new moles appearing, existing moles darkening and growing, and atypical moles found on biopsy. A 2017 review counted four melanoma cases linked in time to melanotan use.
Why does Melanotan 2 cause erections?
MT-2 also switches on MC4R, a melanocortin receptor in the brain involved in sexual function. That effect was strong enough that MT-2 was studied for erectile dysfunction, and PT-141 was developed from it.
References
- Dorr RT, et al. Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study. Life Sci. 1996;58(20):1777-1784. DOI
- Wessells H, et al. Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study. J Urol. 1998;160(2):389-393. PubMed
- Wessells H, et al. Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction. Urology. 2000;56(4):641-646. DOI
- Hadley ME, Dorr RT. Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization. Peptides. 2006;27(4):921-930. DOI
- Habbema L, et al. Risks of unregulated use of alpha-melanocyte-stimulating hormone analogues: a review. Int J Dermatol. 2017;56(10):975-980. DOI
- Cardones AR, Grichnik JM. Alpha-melanocyte-stimulating hormone-induced eruptive nevi. Arch Dermatol. 2009;145(4):441-444. DOI
- Cousen P, et al. Eruptive melanocytic naevi following melanotan injection. Br J Dermatol. 2009. DOI
- Hueso-Gabriel L, et al. Eruptive dysplastic nevi following melanotan use. Actas Dermosifiliogr. 2012;103(4):329-331. DOI
- Hjuler KF, Lorentzen HF. Melanoma associated with the use of melanotan-II. Dermatology. 2014;228(1):34-36. DOI
- Gilhooley E, et al. Melanotan II user experience: a qualitative study of online discussion forums. Dermatology. 2021;237(6):995-999. DOI
- Mallory CW, et al. Melanotan tanning injection: a rare cause of priapism. Sex Med. 2021;9:100298.
- Dreyer BA, et al. Melanotan-induced priapism: a hard-earned tan. BMJ Case Rep. 2019;12(2):e227644. BMJ
- Nelson ME, et al. Melanotan II injection resulting in systemic toxicity and rhabdomyolysis. Clin Toxicol (Phila). 2012. PubMed
- Peters B, et al. Melanotan II: a possible cause of renal infarction: review of the literature and case report. CEN Case Rep. 2020;9(2):159-161. DOI
- Newton J, et al. Nasal tanning sprays: illuminating the risks of a popular TikTok trend. Cutis. 2024;113(1):E3-E4. DOI
- DermNet. Melanotan II. DermNet
Stay sharp,
Joe Mars
The Peptide Report
P.S. Running the numbers on your first vial and want someone to double-check them? Post them inside the Peptides and Biohacking Hub on Skool. Free community, real protocols, and people actually running this stuff. Join here.
