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Peptide Side Effects: What Users Report

15 anonymous reports

Anonymous user report. Not medical advice. Peptides discussed are not FDA-approved for the uses described. Editorial process →

Short answer

The most-reported side effects here are gastrointestinal (nausea, constipation, reflux) on GLP-1 drugs such as semaglutide, tirzepatide and retatrutide; injection-site reactions, water retention and tingling on growth-hormone secretagogues; and nausea, flushing and darkened moles on melanotan. Unapproved vials add an unknown-purity risk. Severe abdominal pain, chest pain, fainting, a hot spreading injection site or an allergic reaction needs urgent care. This is not a dosing recommendation.

Side effects by peptide, by the numbers

Each figure is a phrase match over published confessions, from the data reports linked in the table. One confession can match several phrases, and a denial ("no nausea") is not counted. These are self-reports, not clinical rates. This is not a dosing recommendation.

PeptidePublished confessionsMention any side effectMost mentioned
Retatrutide40670Heart rate or palpitations, 25 (6.2%); Anxiety or panic 12; Fatigue or exhaustion 10; Low mood or anhedonia 10
Tirzepatide12932Heart rate or palpitations, 13 (10.1%); Anxiety or panic 7; Burping 5; Libido 4
BPC-157799Anxiety or panic, 2 (2.5%); Heart rate or palpitations 2; Reflux or heartburn 2; Cramps 1
Semaglutide hub497Burping, 3 (6.1%); Vomiting 3; Anxiety or panic 2; Nausea 2

What users report

This topic currently has 15 tagged published confessions. The notes below are individual stories, not rates.

#120 describes two bad weeks after a short BPC-157 and TB-500 run: nausea, a panic attack, a resting heart rate of 120, insomnia and three periods in one month. #71 describes daily nausea and palpitations on retatrutide, worse after an accidental extra injection. #39 calls retatrutide not worth it: nausea, vomiting and odd skin sensations. #43 lost a third of their hair density on semaglutide. #44 mixed a peptide with bottled water and got an injection-site infection that needed antibiotics.

Not every report is negative: #75 calls younger-looking skin on GHK-Cu the "worst best side effect". Reports of no side effects exist too, and say nothing about the next person.

What regulators and trials say

In GLP-1 trials, gastrointestinal effects (nausea, diarrhoea, vomiting, constipation) are the most common side effects, and labels warn about pancreatitis, gallbladder disease and dehydration. Retatrutide is still in phase 3 trials and is not approved anywhere. Health Canada and the FDA have warned that unapproved peptides can be contaminated, wrongly dosed or mislabelled. See are peptides legal in Canada? and dosing mistakes.

Severe abdominal pain, persistent vomiting, chest pain, fainting, or a hot, spreading injection site need urgent medical care. Related: peptides for weight loss, semaglutide vs tirzepatide, peptides for recovery.

Related topics

Best Peptide StacksPeptides for RecoveryPeptides for Weight LossLL-37 BenefitsMelanotan 2 Side EffectsDSIP BenefitsFOXO4-DRIKPV Side EffectsPeptides and Blood PressurePeptides for DepressionSuccess Stories

Anonymous side-effect reports

before everyone screenshots today's GLP-1 cancer headlines: it's observational data. healthier people take these drugs to begin with, so some of that 30% is selection bias, and the 11,000-woman trial that'll actually prove it hasn't reported yet. that said, I've been on tirz two years and "might lower my cancer risk" is a hell of a side effect to stumble into while trying to fit my old jeans. cautiously, quietly optimistic.

#146
TirzepatideGLP-1

Reta at 2mg per week for 2 weeks, zero side effects, upping to 4mg this week.

#144
Retatrutide

You're gonna call me crazy but here goes, I was taking a GLP-1 and had reached the highest dose of 4.5mg, wasn't working anymore so I started Retatrutide from a top provider with finnrick testing and at the 2mg dose recommended.. At the end of week one I felt nothing so me being the mutant I am I decided screw the side effects if they come though everything in the clinical studies id read screamed not to I upped it to the 4mg dose for week two, still with no side effects. I jumped off week three at 6mg , still no side effects. Every week I kept titrating up by 2mg ..By week six I was at 12mg 😳 not one single side effect. Ive now been on 12mg per week going on 4 months with zero side effects and have lost around 50lbs and still dropping daily .. ive had no issues , no cardio changes and stopped drinking alcohol completely I feel better every day as I am severely overweight and this has been a game changer..My doctor was so happy 😊 (he thinks it's the GLP-1) man if he only knew 🤣

#139
RetatrutideGLP-1

Seeing the latest confession prompted me to tell me Ghk cu story. Ghk cu/ahk cu topical by precise formulations stopped my hair loss drastically within a month where injectable 3mg daily didn't do anything for me. And no it's not an ad just my experience

#127
GHK-Cu

I'm not here to argue about whether the peptide "really" caused this. I'm just telling you what happened to my body, in order. five days of BPC + TB-500. that's all I ran. within two weeks: I couldn't have a normal bowel movement, nausea so bad I kept a trash bag next to the couch, and a panic attack severe enough that I took a Valium for the first time in years. then both knees, not one, BOTH, flared with what feels like tendonitis. muscle twitches. heart rate at 120 just lying in bed waking up. four hours of sleep a night for two solid weeks. and the part nobody warned me about as a woman: I had three periods in one month. first one normal, second one brown with cramps I never get, third one red with no cramps at all. like my hormones got picked up and shaken. I have zero scientific proof it was the peptide. I only know I was fine before the injection and a wreck after, and three weeks out I'm finally leveling back to normal. take that for whatever it's worth.

#120
TB-500BPC-157

Had a traumatic spinal injury and SS31 helped tremendously with some side effects.. It also helped with my raging head aches.

#106
SS-31

1 month on Reta and I’m down 20lbs but here is the plot twist. My balls have unionized and gone full milk-cow mode. I’m talking industrial quantities. Daily masturbation (quality control testing, obviously) now produces enough semen to feed a small village. It’s like my prostate got the memo that we’re in a weight-loss competition and decided to overachieve in the fluid department. I’m out here like “whoa buddy, slow down, I only have two hands and one sock.” Is this a known side effect? Are my testes on Retatrutide too? Should I be concerned or start a side hustle selling “premium farm-fresh” on Etsy? Either way, 10/10 would recommend. Losing weight and gaining superpowers in the bedroom (or shower… or car… look I’m busy okay).

#095
Retatrutide

reta gave me sulfur burps so frickin horrible :( turns out that's the tell you're titrating too fast and your gut motility tanked. dropped back a dose, burps gone in 4 days. it's a signal, not just a side effect.

#088
Retatrutide

the reta cardiovascular thing is real but it's dose-dependent. my RHR was fine at 2-4mg and only climbed once I pushed past 6. everyone screaming about heart rate is maxing the dose because they think more = faster. you don't need 12mg. most people get full results at 4-6 and skip the side effects.

#083
Retatrutide

GHK-Cu didn't regrow my hair. it un-aged my face by a decade instead. I now look younger than my little brother and he will not let it go. worst best side effect of my life.

#075
GHK-Cu

Taking reta for 9 weeks. Max dose 2mg. But i am fed up with sides. Nausea everyday. Cant lift heavy. Now I made a mistake and get another dose in 5th day. Now I cant eat, have very bad skin feeling,heart palpitations and bad mood at all

#071
Retatrutide

things i learned the hard way on retatrutide: the nausea peaks at week 3 not week 1 alcohol becomes literally toxic, one beer = food poisoning sulfur burps mean you're titrating too fast the "ozempic face" thing is real and arrives at month 4 nobody tells you any of this until you post about it

#055
SemaglutideRetatrutide

Reconstituted my first peptide with regular bottled water because I didn't know better. Pinned it for 3 weeks. Got a brutal infection at the injection site that required oral antibiotics. Bacteriostatic water is $4 don't be mee

#044

Semaglutide gave me the worst hair loss of my life :( Lost a third of my hair density in 5 months. Dr said it was the rapid weight loss, not the drug but switched to tirzepatide at a slower titration and my hair kinda grew back so idk

#043
TirzepatideSemaglutide

Dont take reta its not worth it at all, stomach destroyed + daily nausea + vomiting + skin feeling super odd sensation. The struggle is real.

#039
Retatrutide

If a peptide gave you a side effect — or none — submit what happened.

Submit yours

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More confessions from the archive

Community Q&A

What are the side effects of peptides?
It depends on the peptide. GLP-1 drugs mainly cause nausea, constipation and reflux; growth-hormone peptides cause water retention, flushing and tingling; melanotan and PT-141 cause nausea, flushing and darker moles. Injection-site reactions are common to all injected peptides, and research vials add contamination and mislabelling risk.
Are peptide side effects permanent?
Most reported effects, such as nausea or injection-site reactions, fade after stopping. Long-term effects of most research peptides are unknown because they have not been studied in humans.
What are the most common peptide side effects users report?
In this archive, Heart rate or palpitations is the most mentioned phrase for retatrutide (25 of 406 confessions); for tirzepatide it is Heart rate or palpitations (13 of 129). These are phrase counts, not clinical rates.
Does BPC-157 have side effects?
9 of 79 BPC-157 confessions use a side-effect phrase, with Anxiety or panic, 2 (2.5%); Heart rate or palpitations 2; Reflux or heartburn 2; Cramps 1. #120 describes a severe reaction after BPC-157 with TB-500. BPC-157 is not approved and has no long-term human safety data.
Do GLP-1 side effects go away?
In trials, nausea is most common early and tends to ease. Reports in this archive vary: some describe it fading, others (#39, #71) describe daily nausea that did not. Persistent vomiting or severe pain needs medical care.
Does this page give dosing advice?
No. Peptide Confessions does not publish dosing, timing or sourcing guidance.
What are the most common peptide side effects?
By frequency across community accounts: nausea (GLP-1s and tanning peptides), water retention (GH secretagogues), injection site irritation (any injectable), vivid dreams (GH secretagogues), fatigue in early weeks (GLP-1s), and hair shedding at significant weight loss (GLP-1s). The specific profile depends almost entirely on the compound class.
Which peptides have the fewest side effects?
BPC-157 and KPV produce the fewest adverse reports by volume in community accounts. Ipamorelin is the GH secretagogue most consistently described as clean — lacking the cortisol spikes and hunger of older GHRP-class peptides. Among GLP-1s, tirzepatide is more frequently described as better-tolerated than semaglutide, though this varies by individual.
Do peptide side effects go away?
Most acute side effects in community accounts self-resolve within 4–8 weeks as the body adjusts. GLP-1 nausea is the clearest example — described consistently as improving over the first 2 months. Water retention from GH secretagogues is described similarly. Side effects that persist beyond 8 weeks, or worsen rather than improve, appear in a small minority of accounts and are most commonly attributed to dose being too high or escalation too fast.
What happens if you take too much peptide?
Overdose reports in the archive usually describe stronger versions of known side effects: persistent vomiting and being unable to eat on GLP-1s, marked fluid retention and numbness on GH secretagogues, severe nausea and flushing on melanotan. Many began with a misread syringe or a mislabelled vial. Persistent vomiting or dehydration needs urgent medical care. More is not better.

Anonymous first-hand reports plus sourced context — educational only, not medical advice. Editorial policy & corrections.

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