Home / Peptide guides / Retatrutide / Side effects
New study · Oct 14, 2026
Retatrutide side effects: what 13,589 people said online
Research purposes only (investigational) Checked against the published paper Oct 17, 2026
Retatrutide is the triple-agonist shot everyone's watching, and thousands of people are already posting about it. A University of Pennsylvania team just ran those posts through AI and published the first systematic look at what users say they feel. Here's what they found.
Quick facts
- Study: "Self-Reported Adverse Effects Among Social Media Users Taking Nonapproved Retatrutide," Sehgal et al., JAMA Network Open, Oct 14, 2026. A University of Pennsylvania team, with Boston Children's Hospital and Harvard Medical School.
- Type: a cross-sectional analysis of public Reddit posts. Self-reported, not a trial.
- Method: large language models flagged posts about personal use and matched each symptom to standard medical terms (MedDRA). A manual check of 100 posts showed high precision and recall.
- Window: posts from May 2021 to December 2025. Reports of current use dated March 10, 2023 to December 31, 2025.
- What the authors say: the findings are hypothesis-generating and flag signals worth formal drug-safety follow-up.
🧮 Free tool: our mg → mL → units calculator is the converter for semaglutide and tirzepatide vials. Plug in your own vial label and see the math.
The most reported retatrutide side effects
Share of the 7,823 users who described at least one symptom. One person can report several.
| Symptom (as reported) | Users | Share |
|---|---|---|
| Increased appetite | 1,336 | 17.1% |
| Fatigue | 1,188 | 15.2% |
| Increased energy | 970 | 12.4% |
| Nausea | 907 | 11.6% |
| Food cravings | 571 | 7.3% |
| Insomnia | 475 | 6.1% |
| Raised heart rate | 374 | 4.8% |
| Hunger | 366 | 4.7% |
| Constipation | 354 | 4.5% |
| Diarrhea | 345 | 4.4% |
| Bloating (abdominal distension) | 331 | 4.2% |
| Malaise | 318 | 4.1% |
| Muscle growth (muscle hypertrophy) | 317 | 4.1% |
| Weight increased | 305 | 3.9% |
| Anxiety | 301 | 3.8% |
| Fast heartbeat (tachycardia) | 294 | 3.8% |
Source: Table in Sehgal et al., JAMA Network Open, Oct 14, 2026. Plain-English labels; the paper uses MedDRA terms such as "Energy increased," "Food craving" and "Heart rate increased."
By body system
- Gut: 32.5% of users reported a gastrointestinal symptom. Nausea led (11.6%), then constipation (4.5%), diarrhea (4.4%) and bloating (4.2%).
- Mood and sleep: 30.3% reported a psychiatric-category symptom, led by insomnia (6.1%) and anxiety (3.8%).
- Heart: "heart rate increased" came up for 4.8% of users, and 5.9% reported a cardiac-category symptom such as a fast heartbeat (3.8%) or palpitations (1.9%).
- Muscle: 14.4% reported a musculoskeletal symptom. Muscle growth (4.1%) was the most common, ahead of muscle loss (2.0%).
The surprise: it doesn't look like the trials
In the phase 2 obesity trial, gut effects (nausea, diarrhea, vomiting and constipation) were the most common side effects. On Reddit, gut symptoms were common but not dominant. Appetite, general (fatigue, energy), muscle, sleep and heart-rate reports stood out instead. The pattern also differed from the same team's earlier Reddit study of semaglutide and tirzepatide, where reports were more concentrated in nausea, vomiting and gut-motility categories. The authors suggest the difference may come from retatrutide's extra target, the glucagon receptor, since it's the only triple agonist in its class. They also flag the appetite finding as unexpected, given the big weight losses in trials.
Read this before you quote it
These are things people wrote online about products they bought outside the trials. The researchers point out that product identity, purity, dose and medical history couldn't be verified, and that the results may reflect dose or product differences, stacking several peptides, reconstitution practices, who posts on Reddit, or symptoms blamed on the drug that came from something else. So the study can't tell you how often a side effect happens, whether retatrutide caused it, or how it compares to approved GLP-1s. It's a map of what to test next, and prospective studies are the next step.
Wondering when it will be approved? See the retatrutide release date & FDA status tracker. Want the trial data? Our retatrutide guide covers the phase 3 TRIUMPH results, status and FAQs. Comparing options? See all four GLP-1s side by side. Thinking about where a vial came from? Read how to tell if a peptide source is legit.
Get the next big peptide study first
New results like this, explained plainly in five minutes, every Friday. Free.
Retatrutide side effects FAQ
What are the most common retatrutide side effects people report online?
In the Penn team's JAMA Network Open study of Reddit posts, the most common self-reported symptoms were increased appetite (17.1% of 7,823 users), fatigue (15.2%), increased energy (12.4%), nausea (11.6%), food cravings (7.3%), insomnia (6.1%) and a raised heart rate (4.8%).
Is this study a clinical trial?
No. It's a cross-sectional analysis of public Reddit posts, where people described their own experiences. Nobody's product, dose or health history could be verified. The authors call the findings hypothesis-generating.
How is this different from the retatrutide trials?
In the phase 2 obesity trial, gastrointestinal events (nausea, diarrhea, vomiting and constipation) were most common. In the Reddit posts, gut symptoms were common but not dominant. Appetite, energy, sleep, heart-rate and muscle-related reports stood out more.
Why would people report increased appetite on a weight-loss drug?
The authors call it unexpected and don't have an answer yet. They list possible explanations, including product or dose differences, stacking several peptides, reconstitution practices, who posts on Reddit, or symptoms blamed on the drug that came from something else.
Is retatrutide FDA-approved?
No. It's investigational and in phase 3 trials. The study notes the FDA has warned that nonapproved retatrutide products are being sold directly to consumers, including ones labeled for research or not for human consumption.
Sources: Sehgal et al., JAMA Network Open, Oct 14, 2026 (doi:10.1001/jamanetworkopen.2026.38929); Penn Engineering news release.
Research purposes only. Not FDA-approved for human use, and products vary in quality. Findings above are from the studies cited.
Not medical advice. Education only. We don't sell anything or tell you what to take. Label doses are there so you can follow along with your prescriber. Talk to a licensed clinician about your health.