--- title: "Retatrutide Side Effects: Trial Data So Far" description: "Retatrutide side effects in the phase 2 and TRIUMPH trials: nausea, diarrhea, skin sensations, heart rate. Investigational and approved nowhere yet." url: https://mingo.fit/blog/retatrutide-side-effects/ language: en published: 2026-11-08 --- # Retatrutide Side Effects: Trial Data So Far Retatrutide side effects in clinical trials have been mostly digestive: nausea, diarrhea, constipation and vomiting, generally more common at higher doses. The TRIUMPH phase 3 trials also found more dysesthesia, an abnormal skin sensation, than with placebo, and the phase 2 trial found a rise in heart rate. Retatrutide is investigational and approved nowhere, so everything below comes from trials. Mingo is a GLP-1 tracker app; this guide summarizes published trials and Lilly's announced results and is not medical advice. Two kinds of sources appear below, and each result says which one it is. A **paper** has been peer reviewed and published in a medical journal. A **topline** is a press release from Eli Lilly, the company developing retatrutide, issued before the full results are peer reviewed. Lilly says the detailed results of each trial will be published in peer-reviewed journals. ## Where retatrutide stands Retatrutide is a once-weekly injection that activates three hormone receptors: GIP, GLP-1 and glucagon ([phase 2 paper, NEJM 2023](https://pubmed.ncbi.nlm.nih.gov/37366315/)). For what the trials found on weight, see our [retatrutide overview](https://mingo.fit/blog/retatrutide-glp-1-weight-loss/). No regulator has approved it. In July 2026, Lilly called retatrutide "an investigational molecule that cannot be legally sold or marketed for human use," and said it is completing the manufacturing data package for a Biologics License Application and plans to submit retatrutide to the FDA in the first quarter of 2027 ([Lilly topline, July 23, 2026](https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-successful-two-additional)). In May 2026 Lilly also said it is legally available only to participants in Lilly's clinical trials ([Lilly topline, May 21, 2026](https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-powerful-weight-loss)). These are the trials this guide draws on, with the type and date of each source: | Trial | Who took part | Length | Doses tested | Source | |---|---|---|---|---| | Phase 2 | 338 adults with obesity, or overweight plus a weight-related condition | 48 weeks | 1, 4, 8 and 12 mg | Paper: NEJM, online June 26, 2023 | | TRIUMPH-4 | 445 adults with obesity or overweight and knee osteoarthritis, without diabetes | 68 weeks | 9 and 12 mg | Topline: Lilly, December 11, 2025 | | TRIUMPH-1 | 2,339 adults with obesity or overweight and a weight-related condition, without diabetes | 80 weeks | 4, 9 and 12 mg | Topline: Lilly, May 21, 2026. Paper: NEJM, online September 29, 2026 | | TRIUMPH-2 | 1,152 adults with type 2 diabetes and a BMI of 27 or more | 80 weeks | 4, 9 and 12 mg | Topline: Lilly, July 23, 2026. Paper: The Lancet, online September 29, 2026 | | TRIUMPH-3 | 1,949 adults with a BMI of 35 or more and established cardiovascular disease | 80 weeks | 9 and 12 mg | Topline: Lilly, July 23, 2026 | Every trial compared retatrutide with placebo, and the TRIUMPH trials were double-blind: neither the participants nor the researchers knew who was getting which treatment until the trial was over ([National Cancer Institute dictionary](https://www.cancer.gov/publications/dictionaries/cancer-terms/def/double-blind-study)). We found no peer-reviewed paper for TRIUMPH-3 or TRIUMPH-4 in PubMed as of October 31, 2026, so their numbers below are Lilly's. ## Side effects in the phase 2 trial The phase 2 trial is the earliest source in this guide ([Jastreboff et al., NEJM 2023](https://pubmed.ncbi.nlm.nih.gov/37366315/)). Its abstract reports that: - The most common adverse events on retatrutide were gastrointestinal. - They were dose-related and mostly mild to moderate. - They were partly reduced in the groups that started on a lower dose. - Heart rate rose with the dose, peaked at 24 weeks and declined after that. The abstract doesn't give a rate for each symptom. The phase 3 results below do. ## Side effects in the TRIUMPH trials In every TRIUMPH result so far, digestive effects were the most common. Lilly's TRIUMPH-1 and TRIUMPH-4 toplines describe the types of adverse events as generally consistent with other incretin-based medicines, the GLP-1 family. Each trial enrolled different people, and TRIUMPH-4 ran 68 weeks rather than 80, so their rates can't be ranked against each other or against an approved drug's label. ### TRIUMPH-1: adults without diabetes Lilly's topline for TRIUMPH-1 ([May 21, 2026](https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-powerful-weight-loss)) lists the most common adverse events, and separately the rate of urinary tract infections: | Side effect (TRIUMPH-1 topline) | 4 mg | 9 mg | 12 mg | Placebo | |---|---|---|---|---| | Nausea | 28.6% | 38.4% | 42.4% | 14.8% | | Diarrhea | 25.2% | 34.1% | 32.0% | 13.5% | | Constipation | 23.8% | 25.9% | 26.1% | 10.9% | | Vomiting | 10.6% | 22.8% | 25.3% | 4.8% | | Upper respiratory tract infection | 14.2% | 12.2% | 13.1% | 11.6% | | Urinary tract infection | 7.5% | 8.8% | 8.4% | 5.3% | Lilly says the urinary tract infections were generally mild to moderate and most resolved during treatment. The peer-reviewed TRIUMPH-1 paper ([NEJM, September 29, 2026](https://pubmed.ncbi.nlm.nih.gov/42814954/)) also reports gastrointestinal events as the most common adverse events. The rates in the table are Lilly's topline figures. ### TRIUMPH-2: adults with type 2 diabetes The TRIUMPH-2 paper ([Bellido et al., The Lancet, September 29, 2026](https://pubmed.ncbi.nlm.nih.gov/42810372/)) gives rates for diarrhea and nausea. Lilly's topline ([July 23, 2026](https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-successful-two-additional)) adds three more: | Side effect (TRIUMPH-2) | 4 mg | 9 mg | 12 mg | Placebo | Source | |---|---|---|---|---|---| | Diarrhea | 27% | 34% | 34% | 13% | Paper | | Nausea | 14% | 21% | 28% | 8% | Paper | | Constipation | 14.0% | 16.2% | 16.8% | 9.4% | Topline | | Decreased appetite | 5.8% | 12.3% | 17.1% | 4.5% | Topline | | Vomiting | 5.5% | 10.2% | 15.7% | 4.2% | Topline | The paper also reports seven deaths during the trial: two in the 4 mg group, three in the 9 mg group, one in the 12 mg group and one on placebo. The investigators judged all of them unrelated to the study treatment. The authors describe the safety profile as generally consistent with other medicines that act on the GLP-1 receptor. ### TRIUMPH-3: adults with heart disease TRIUMPH-3 tested only the two higher doses. From Lilly's topline ([July 23, 2026](https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-successful-two-additional)): | Side effect (TRIUMPH-3 topline) | 9 mg | 12 mg | Placebo | |---|---|---|---| | Diarrhea | 30.1% | 24.4% | 8.7% | | Nausea | 21.7% | 22.4% | 5.8% | | Constipation | 18.0% | 15.7% | 7.1% | | Decreased appetite | 13.5% | 14.5% | 3.0% | | High blood sugar (hyperglycemia) | 3.9% | 3.1% | 13.4% | High blood sugar was the one listed event that was more common on placebo. ### TRIUMPH-4: adults with knee osteoarthritis Lilly announced TRIUMPH-4 as retatrutide's first successful phase 3 trial. From Lilly's topline ([December 11, 2025](https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-weight-loss-average)): | Side effect (TRIUMPH-4 topline) | 9 mg | 12 mg | Placebo | |---|---|---|---| | Nausea | 38.1% | 43.2% | 10.7% | | Diarrhea | 34.7% | 33.1% | 13.4% | | Constipation | 21.8% | 25.0% | 8.7% | | Vomiting | 20.4% | 20.9% | 0.0% | | Decreased appetite | 19.0% | 18.2% | 9.4% | ## How many people stopped retatrutide because of side effects? Stopping treatment because of adverse events was more common on the higher doses than on placebo in every trial, though not always in step with the dose: | Stopped because of adverse events | 4 mg | 9 mg | 12 mg | Placebo | |---|---|---|---|---| | TRIUMPH-1 (topline, May 21, 2026) | 4.1% | 6.9% | 11.3% | 4.9% | | TRIUMPH-2 (paper, September 29, 2026; adverse events or death) | 4% | 12% | 8% | 5% | | TRIUMPH-3 (topline, July 23, 2026) | not tested | 9.8% | 13.5% | 4.8% | | TRIUMPH-4 (topline, December 11, 2025) | not tested | 12.2% | 18.2% | 4.0% | Two details from Lilly's TRIUMPH-4 topline change how its row reads. Overall, about as many people stopped treatment on retatrutide as on placebo. And the adverse-event discontinuations were highly correlated with starting BMI and included people who stopped because of what Lilly calls perceived excessive weight loss. Among participants who started with a BMI of 35 or more, 8.8% on 9 mg and 12.1% on 12 mg stopped because of adverse events, compared with 4.8% on placebo. ## What is dysesthesia on retatrutide? Dysesthesia is a condition in which a sense, especially touch, is distorted, so an ordinary touch can feel unpleasant or painful ([National Cancer Institute dictionary](https://www.cancer.gov/publications/dictionaries/cancer-terms/def/dysesthesia)). It was reported more often with retatrutide than with placebo in all four TRIUMPH trials: | Dysesthesia | 4 mg | 9 mg | 12 mg | Placebo | |---|---|---|---|---| | TRIUMPH-4 (topline, December 11, 2025) | not tested | 8.8% | 20.9% | 0.7% | | TRIUMPH-1 (topline, May 21, 2026) | 5.1% | 12.3% | 12.5% | 0.9% | | TRIUMPH-2 (paper, September 29, 2026) | 4% | 6% | 7% | 1% | | TRIUMPH-3 (topline, July 23, 2026) | not tested | 6.4% | 6.4% | 1.3% | How Lilly describes it: - **TRIUMPH-4:** generally mild, and it rarely led people to stop treatment. - **TRIUMPH-1:** generally mild to moderate, most cases resolved during treatment, and most participants kept taking retatrutide. - **TRIUMPH-2 and TRIUMPH-3:** generally mild to moderate, and most resolved during treatment. The phase 2 abstract doesn't mention dysesthesia, and the toplines don't say what causes it or where on the body it was felt. ## Heart rate, blood pressure and heart events ### Heart rate The phase 2 trial found heart rate increases that grew with the dose and declined after their peak, as listed above. None of Lilly's TRIUMPH toplines, nor the TRIUMPH-1 and TRIUMPH-2 paper abstracts, report heart rate, so we have no phase 3 heart-rate figures to give. ### Low blood pressure In the TRIUMPH-2 paper, low blood pressure (hypotension) was reported in 1% on 4 mg, 5% on 9 mg and 6% on 12 mg, compared with less than 1% on placebo. ### The TRIUMPH-3 heart-event result TRIUMPH-3 enrolled people with established heart or blood vessel disease, and its main goal was weight loss. It also counted major adverse cardiovascular events (MACE) and compared the pooled 9 mg and 12 mg groups with placebo. Lilly reports ([July 23, 2026](https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-successful-two-additional)): - **MACE-3** (cardiovascular death, heart attack or stroke): 27 events on retatrutide and 23 on placebo, a hazard ratio of 1.12 (95% confidence interval 0.64 to 1.96). - **MACE-5** (death from any cause, heart attack, stroke, a heart failure event, or coronary revascularization, a procedure to restore blood flow to the heart): 44 events on retatrutide and 52 on placebo, a hazard ratio of 0.82 (95% confidence interval 0.55 to 1.22). A hazard ratio above 1 means more events on retatrutide, and below 1 means fewer. Both confidence intervals include 1, so this result doesn't show that retatrutide raises or lowers the risk of these events. Lilly says these events occurred less often than anticipated in both groups. These are the pre-specified analyses; Lilly also gave on-treatment figures (MACE-5: 0.73, 0.47 to 1.12; MACE-3: 0.92, 0.51 to 1.65), but those were not planned in advance. Lilly lists cardiovascular and renal outcomes among the areas it is still studying. ## How long do retatrutide side effects last? The sources give only partial answers: - **Heart rate:** in the phase 2 trial, the increase peaked and then declined, as described above. - **Dysesthesia and urinary tract infections:** Lilly says most resolved during treatment. - **Digestive effects:** none of the sources above say how long they lasted or when they started. Since none of these sources gives a duration for nausea, diarrhea or constipation, the practical way to see your own pattern is to log symptoms day by day and look at how they line up with each dose. ## What has the FDA said about retatrutide sold online? Products sold as retatrutide outside the trials have been marketed online, some labeled "for research purposes." The FDA's page on [unapproved GLP-1 drugs used for weight loss](https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss) (content current as of October 1, 2026) says: - Retatrutide cannot be used in compounding under federal law. It is not a component of any FDA-approved drug and has not been found safe and effective for any condition. - The FDA has warned telehealth companies for marketing unapproved drugs such as retatrutide, ingredient distributors for selling it to compounders, and outsourcing facilities for repackaging it. - The FDA has warned companies that illegally sold unapproved drugs containing retatrutide falsely labeled "for research purposes" or "not for human consumption," products that were sold directly to consumers for human use with dosing instructions. - The agency urges consumers not to buy these products, which are of unknown quality and may be harmful to their health. In December 2024, the FDA posted four warning letters to companies for selling unapproved GLP-1 products, including retatrutide ([FDA Roundup, December 17, 2024](https://www.fda.gov/news-events/press-announcements/fda-roundup-december-17-2024)). The trial results in this guide don't apply to these products, whose quality the FDA calls unknown. If you have used such a product and feel unwell, talk to a doctor and tell them what you took. The FDA's page also asks patients to report side effects and quality problems to its MedWatch program. ## If you are in a trial: reporting side effects In a clinical trial, you follow the trial procedures and report any issues or concerns to the researchers, according to the [National Institute on Aging](https://www.nia.nih.gov/health/clinical-trials-and-studies/what-are-clinical-trials-and-studies). When you join, you sign an informed consent form showing you understand what to expect as a participant. General tips for nausea, constipation and other common effects are in our [GLP-1 side effects guide](https://mingo.fit/blog/glp-1-side-effects-what-to-expect-and-how-to-manage/) and our [tirzepatide side effects guide](https://mingo.fit/blog/tirzepatide-side-effects/). Before trying one, including an over-the-counter remedy, ask your study team whether it fits the trial's procedures. ## Keeping a side-effect log in Mingo Mingo, our app, lists retatrutide for trial participants, along with Ozempic, Wegovy, the Wegovy pill, Rybelsus, Mounjaro, Zepbound, Foundayo, and compounded semaglutide and tirzepatide. You log each weekly injection with its dose, the injection site on a body map of 12 sites (with optional left and right alternation) and notes, and rate how you feel on 18 built-in symptoms, each on a 0 to 10 slider. The built-in symptoms include nausea, constipation and diarrhea, the digestive effects most reported in the trials, plus stomach pain, bloating, suppressed appetite and fatigue. Vomiting and dysesthesia are not built in, so add vomiting and skin sensitivity as your own symptoms, along with anything else you want to follow, such as dizziness. Each symptom can be charted against your estimated medication level, which Mingo calculates from the doses you log and a half-life model. It is an estimate, not a blood test, and it can only reflect the dose you enter: in a blinded trial you may not know your treatment or dose, so the symptom log is the more useful part. Your weight chart is colored by the dose you were on, with a marker at each new dose, so you can see whether a rough week lines up with a dose change. Mingo reminds you on dose day, can give you a heads-up before, and nudges you 2 hours later if the dose isn't logged. Meals can be logged by photo, voice, text or barcode, with daily protein, fiber and water targets. Meal photos, voice notes and descriptions are sent to Mingo's server to estimate nutrients; the log itself stays on your phone, with no account. Before a study visit, export a PDF report of your doses, estimated levels, weight, food and side effects for any period. It doesn't replace the trial's own reporting, but it gives you and the study team the same record to look at. Mingo Pro is required to keep logging new entries after the first ones; reminders, the medication-level chart and the PDF report stay free. ## Sources - Jastreboff AM, Kaplan LM, Frías JP, et al. [Triple-hormone-receptor agonist retatrutide for obesity: a phase 2 trial](https://pubmed.ncbi.nlm.nih.gov/37366315/). N Engl J Med. 2023;389(6):514-526. Paper, published online June 26, 2023. - Jastreboff AM, Kaplan LM, Davies MJ, et al. [Retatrutide, a triple hormone receptor agonist, for treatment of obesity](https://pubmed.ncbi.nlm.nih.gov/42814954/) (TRIUMPH-1). N Engl J Med. Paper, published online September 29, 2026. - Bellido V, le Roux CW, Ekinci EI, et al. [Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2)](https://pubmed.ncbi.nlm.nih.gov/42810372/). Lancet. 2026;408(10563):1455-1472. Paper, published online September 29, 2026. - Eli Lilly and Company. [TRIUMPH-4 topline results](https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-weight-loss-average). Press release, December 11, 2025. - Eli Lilly and Company. [TRIUMPH-1 topline results](https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-powerful-weight-loss). Press release, May 21, 2026. - Eli Lilly and Company. [TRIUMPH-2 and TRIUMPH-3 topline results](https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-successful-two-additional). Press release, July 23, 2026. - U.S. Food and Drug Administration. [FDA's concerns with unapproved GLP-1 drugs used for weight loss](https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss). Content current as of October 1, 2026. - U.S. Food and Drug Administration. [FDA Roundup: December 17, 2024](https://www.fda.gov/news-events/press-announcements/fda-roundup-december-17-2024). - National Cancer Institute. [Dysesthesia, NCI Dictionary of Cancer Terms](https://www.cancer.gov/publications/dictionaries/cancer-terms/def/dysesthesia). - National Institute on Aging. [What are clinical trials and studies?](https://www.nia.nih.gov/health/clinical-trials-and-studies/what-are-clinical-trials-and-studies) Content reviewed March 22, 2023. ## Frequently asked questions ### What are the most common side effects of retatrutide? Digestive ones. Nausea, diarrhea, constipation, vomiting and decreased appetite led the lists in the TRIUMPH trials, each reported more often than on placebo and generally more often at the higher doses. The phase 2 paper described these effects as mostly mild to moderate. If one is severe or won't go away, tell your study team. ### Does retatrutide cause skin sensitivity? It can. Dysesthesia, a distorted sense of touch that can make ordinary contact feel unpleasant or painful, was reported more often with retatrutide than with placebo in all four TRIUMPH trials. Lilly describes these events as generally mild or mild to moderate, and for TRIUMPH-1, 2 and 3 it says most resolved during treatment. Note when it happens and where, and report it to the study team. ### Does retatrutide raise your heart rate? In the phase 2 trial it did: heart rate went up with the dose, peaked about halfway through the trial and then came down. Lilly's TRIUMPH press releases and the TRIUMPH-1 and TRIUMPH-2 abstracts don't report heart rate. TRIUMPH-3, in people with heart disease, did not settle whether retatrutide changes the risk of heart attack or stroke. ### Is retatrutide bought online the same as the drug in the trials? There is no way to know. Retatrutide is not approved anywhere, and Lilly says it is legally available only to people in its clinical trials. The FDA says products sold as retatrutide for research or not for human consumption are of unknown quality and may be harmful, and it urges consumers not to buy them. ### When will retatrutide be approved? Nobody can say yet. No regulator has approved it. Lilly has said it plans to apply to the FDA, and approval depends on the agency's review. Until a regulator approves it, retatrutide is an investigational drug used only in clinical trials. ### Can I track retatrutide side effects in Mingo? Yes, if you take it in a trial. Mingo lists retatrutide for trial participants: you can log each weekly injection, rate built-in symptoms such as nausea or constipation, and add your own, such as vomiting or skin sensitivity. A personal log doesn't replace reporting to your study team, but a PDF of it can help at study visits.