Retatrutide Side Effects: What Clinical Trials Show
Clinical trials have most often reported gastrointestinal adverse events including nausea, diarrhea, constipation and vomiting among participants receiving retatrutide.
Here is what the current trial evidence actually shows, what researchers have reported about less familiar effects, and what remains unknown while retatrutide is still investigational.
Retatrutide remains investigational and is not currently FDA approved. This page discusses clinical-trial findings for educational purposes. It is not medical advice, dosing guidance, sourcing information or a substitute for individualized care from a qualified healthcare professional.
Retatrutide side effects are becoming an important question as more clinical-trial results become available. The most frequently reported adverse events in retatrutide studies have included gastrointestinal issues such as nausea, diarrhea, constipation and vomiting.
Retatrutide is an investigational triple hormone receptor agonist that targets GIP, GLP-1 and glucagon receptors. It is not currently FDA approved, so information about retatrutide side effects comes from clinical trials rather than an FDA-approved prescribing label.
If you are looking for broader information about the medication, visit our retatrutide support hub.
What Are the Most Common Retatrutide Side Effects?
The most commonly reported retatrutide side effects in Phase 3 research have primarily involved the gastrointestinal system. Trial participants reported nausea, diarrhea, constipation and vomiting at varying rates depending on the studied dose.
In the Phase 3 TRIUMPH-1 trial, Lilly reported the following adverse events:
| Reported adverse event | 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% |
These percentages describe adverse events reported during the trial. They do not establish that every event was caused by retatrutide.
You can review the TRIUMPH-1 Phase 3 results from Eli Lilly for the reported trial data.
Does Retatrutide Cause Nausea?
Nausea is one of the most commonly reported retatrutide side effects in clinical trials. In TRIUMPH-1, nausea was reported by 28.6% of participants receiving 4 mg, 38.4% receiving 9 mg and 42.4% receiving 12 mg, compared with 14.8% receiving placebo.
Because these are clinical-trial data, a more precise way to interpret the results is that nausea was reported more frequently among participants receiving retatrutide than among those receiving placebo.
People noticing appetite changes alongside nausea may also find our guide to retatrutide food noise useful.
Does Retatrutide Cause Diarrhea?
Diarrhea was another frequently reported gastrointestinal event. In TRIUMPH-1, diarrhea was reported by 25.2% of participants at 4 mg, 34.1% at 9 mg and 32.0% at 12 mg.
This makes diarrhea an important part of the current retatrutide safety data, although individual experiences can vary.
Can Retatrutide Cause Constipation?
Constipation was also reported during retatrutide clinical trials. In TRIUMPH-1, approximately one-quarter of participants receiving retatrutide reported constipation, compared with 10.9% of participants receiving placebo.
Someone experiencing changing digestive patterns may find it useful to record symptoms over time rather than relying on memory alone. Our Retatrutide Tracker is designed to help organize observations, symptoms, food noise, progress notes and questions for a healthcare professional.
Does Retatrutide Cause Vomiting?
Vomiting was reported less frequently than nausea but was still among the notable gastrointestinal retatrutide side effects. In TRIUMPH-1, vomiting was reported by 10.6% of participants at 4 mg, 22.8% at 9 mg and 25.3% at 12 mg, compared with 4.8% receiving placebo.
Can Retatrutide Cause Skin Sensitivity or Tingling?
Clinical trials have also reported dysesthesia, which refers to abnormal or unpleasant sensations that can include heightened sensitivity, tingling or other unusual skin sensations.
In TRIUMPH-1, dysesthesia was reported by 5.1% of participants at 4 mg, 12.3% at 9 mg and 12.5% at 12 mg, compared with 0.9% receiving placebo.
This is one of the less familiar adverse events reported with retatrutide and may be especially useful to track because people may not immediately associate changing skin sensations with a clinical-trial finding.
Does Retatrutide Affect Heart Rate?
Earlier Phase 2 research published in the New England Journal of Medicine reported dose-dependent increases in heart rate. The increases peaked around week 24 and then declined.
This finding came from Phase 2 research and should not be confused with the frequency table of common gastrointestinal adverse events reported in the later Phase 3 trial.
Are Retatrutide Side Effects Dose-Related?
Some reported retatrutide side effects occurred more frequently at higher studied doses, but the pattern was not identical for every adverse event.
For example, nausea and vomiting were reported more often in the higher-dose groups in TRIUMPH-1. Diarrhea and constipation did not increase in a perfectly linear pattern across every dose.
That is why it is more accurate to look at individual trial results rather than assume that every adverse event necessarily increases in direct proportion to dose.
Do Retatrutide Side Effects Cause People to Stop Treatment?
Some participants discontinued treatment because of adverse events. In TRIUMPH-1, discontinuation because of adverse events occurred in 4.1% of the 4 mg group, 6.9% of the 9 mg group and 11.3% of the 12 mg group, compared with 4.9% of participants receiving placebo.
Experiencing an adverse event and discontinuing treatment because of an adverse event are not the same thing, so both numbers are useful when interpreting retatrutide clinical-trial safety data.
When Do Retatrutide Side Effects Happen?
People searching for information about retatrutide side effects often want to know not only what was reported, but when symptoms may appear. Earlier Phase 2 research found that gastrointestinal adverse events occurred particularly during dose escalation and were generally described as mild to moderate in severity.
That does not mean every person would experience the same pattern. Clinical trials describe what happened across groups of participants, while an individual experience can differ in timing, intensity and duration.
This is one reason tracking can be useful. Instead of simply recording that nausea or constipation occurred, a person can note when the symptom started, whether it changed over time and what questions they want to discuss with a healthcare professional.
How Long Do Retatrutide Side Effects Last?
There is not one reliable timeline that applies to everyone. Clinical-trial reports provide rates of adverse events across study populations, but they do not mean that a particular symptom will last a specific number of hours or days for an individual person.
For someone following retatrutide side effects, the more useful approach is to pay attention to patterns: when a symptom appeared, whether it persisted, whether its intensity changed and whether it affected eating, hydration or normal daily activities.
Persistent, severe or concerning symptoms should be discussed with a qualified healthcare professional rather than managed solely from general information found online.
What Should You Track if You Experience Retatrutide Side Effects?
Tracking symptoms can help organize what happened, when it happened and whether the pattern changed over time. It is not a substitute for medical advice, diagnosis or treatment.
- Nausea
- Vomiting
- Diarrhea
- Constipation
- Appetite changes
- Food noise
- Unusual skin sensations
- Hydration
- Energy and fatigue
- When symptoms began
- Whether symptoms improved or persisted
- Questions to discuss with a healthcare professional
If you are preparing to organize baseline information, see what to track before starting retatrutide.
For broader organization, Reta Support also provides a GLP-1 tracker app for keeping weekly observations and provider-prep questions together.
Retatrutide Side Effects vs Other GLP-1 Medications
Retatrutide is not simply another GLP-1 receptor agonist. It targets GIP, GLP-1 and glucagon receptors, which is why comparisons with other medications need context.
Our retatrutide vs tirzepatide guide explains important differences between the two investigational or approved treatment approaches.
For broader experiences involving appetite and cravings, see our guide to food noise on GLP-1.
Is Retatrutide FDA Approved?
No. Retatrutide remains investigational and is not currently approved by the U.S. Food and Drug Administration.
Eli Lilly provides current information about the development program on its retatrutide information page.
Because retatrutide does not yet have an FDA-approved prescribing label, information about retatrutide side effects should be described as clinical-trial findings rather than official prescribing-label side effects or warnings.
When Should You Talk With a Healthcare Professional?
Persistent, severe, unusual or concerning symptoms should be discussed with a qualified healthcare professional. Clinical-trial information can provide context, but it cannot determine what a symptom means for an individual person.
Keeping a record of symptoms, timing and questions may make those conversations easier. You can also connect with others discussing real-world GLP-1 experiences in the Reta Support GLP-1 Community.
Retatrutide Side Effects: The Bottom Line
The current clinical-trial evidence shows that the most frequently reported retatrutide side effects include gastrointestinal adverse events such as nausea, diarrhea, constipation and vomiting. Clinical trials have also reported dysesthesia and changes in heart rate.
Retatrutide remains investigational, so the evidence will continue to evolve as additional Phase 3 results, peer-reviewed publications and regulatory information become available.
For people following the research, the most useful approach is to distinguish between confirmed clinical-trial findings, personal experiences and assumptions about retatrutide side effects.
Frequently Asked Questions About Retatrutide Side Effects
Does retatrutide cause nausea?
Nausea was one of the most frequently reported adverse events among participants receiving retatrutide in clinical trials. Rates varied by studied dose.
Can retatrutide cause constipation?
Constipation was reported in retatrutide clinical trials and occurred more frequently among participants receiving retatrutide than among participants receiving placebo in TRIUMPH-1.
Does retatrutide cause vomiting?
Vomiting was reported in the Phase 3 TRIUMPH-1 trial, with higher percentages reported in the higher-dose groups.
Can retatrutide cause skin sensitivity?
Dysesthesia, an abnormal or unpleasant sensation that may include heightened sensitivity or tingling, has been reported in retatrutide clinical trials.
Are retatrutide side effects worse at higher doses?
Some adverse events were reported more frequently at higher studied doses, but the pattern was not identical for every event.
Is retatrutide FDA approved?
No. Retatrutide remains investigational and does not currently have an FDA-approved prescribing label.
Track the pattern, not just the symptom.
RetaTracker can help organize symptoms, food noise, hydration, weekly observations and questions you want to bring to a healthcare professional.
Reta Support provides educational information and organization tools. Clinical-trial information does not diagnose a symptom or determine what it means for an individual person. Persistent, severe, unusual or concerning symptoms should be discussed with a qualified healthcare professional.