Mazdutide Side Effects: What Studies and Users Report
What FDA labels, clinical studies and people who use Mazdutide report, how strong that evidence is, and what is still unknown.
Side effects reported in studies
Side effects reported in published studies, strongest design first. Frequencies are quoted as the source gives them; animal results are labelled.
| Side effect | How common | Study type | Source |
|---|---|---|---|
| Vomiting, nausea, diarrhea | vomiting 53.1% vs 1.3%; nausea 46.9% vs 3.2%; diarrhea 39.4% vs 6.5% | Human RCTn = 461 | JAMA 2026, PMID 42251595 |
| Gastrointestinal events“Mazdutide was generally safe, although the incidence of gastrointestinal adverse events was higher for mazdutide than for dulaglutide.” | Frequency not stated | Human RCTn = 731 | Nature 2026, PMID 41407860 |
| Gastrointestinal events and decreased appetite | most common | Human RCT | EClinicalMedicine 2021, PMID 34430840 |
| Gastrointestinal side effects“Participants who received Mazdutide had a higher risk of transient mild or moderate gastrointestinal side effects.” | Frequency not stated | Meta-analysisn = 680 | Frontiers in endocrinology 2024, PMID 38440786 |
Overall safety findings
What studies said about safety as a whole, without naming a specific effect.
| Finding | How common | Study type | Source |
|---|---|---|---|
| Discontinuation due to adverse events | 20% discontinued on 16 mg | Human RCTn = 179 | The lancet. Diabetes & endocrinology 2026, PMID 42628555 |
| Common adverse events | most common | Human RCTn = 320 | Nature 2026, PMID 41407859 |
| Discontinuation due to adverse events | 1.5% (4 mg), 0.5% (6 mg), 1.0% placebo | Human RCTn = 610 | The New England journal of medicine 2025, PMID 40421736 |
| Common adverse events | diarrhea 36%, decreased appetite 29%, nausea 23%, vomiting 14%, hypoglycemia 10% (8% placebo) | Human RCT | Diabetes care 2024, PMID 37943529 |
| Common adverse events | most common | Human RCTn = 248 | Nature communications 2023, PMID 38092790 |
What users report
Side effects people describe from their own use of Mazdutide, quoted from 21 Reddit threads we read in r/PeptideGuide, r/Peptides and r/Retatrutide (searched 11 Oct 2026). Each count is the number of different people in those threads, not how common the effect is. These reports are unverified: products bought outside a pharmacy are often mislabelled or impure, and many people take several compounds at once.
| What people noticed | People reporting it | In their words |
|---|---|---|
| Nausea | 2 | “mostly nausea (especially if I eat before a workout — even a banana before running made me feel sick)” r/Retatrutide, Oct 2025“I experienced serious nausea and became very irritable but it wasn’t bad enough for me to quit.” r/Peptides, Aug 2024Also taking other compounds |
| Acid reflux or heartburn | 1 | “heart burn, especially in the 3 days after the shot.” r/Retatrutide, Oct 2025 |
| Tiredness or lethargy | 1 | “I felt a bit more tired than usual” r/Peptides, Aug 2024Also taking other compounds |
| Irritability or mood changes | 1 | “became very irritable” r/Peptides, Aug 2024Also taking other compounds |
| Headache | 1 | “I did have some headaches and occasional constipation” r/Peptides, Aug 2024Also taking other compounds |
| Constipation | 1 | “occasional constipation” r/Peptides, Aug 2024Also taking other compounds |
| Increased hunger | 1 | “my hunger has gone up significantly compared to when I was loading up on Mazdu” r/Retatrutide, Apr 2026Also taking other compounds |
A symptom others mention is not proof that it is harmless. If you have anything on the urgent list below, get care whatever others report.
What is not known
- How common each effect is at the doses people use outside of studies.
- Effects that take longer to appear than the length of the published studies.
- How Mazdutide interacts with other medicines and supplements.
- Whether research-grade products, which are not checked by the FDA, behave like the material used in studies.
When to get medical help
This is not a complete list. A doctor or pharmacist can help you judge whether a symptom is related.
Most common adverse events
In the higher-dose phase 3 trial, vomiting affected 53.1% on mazdutide against 1.3% on placebo, nausea 46.9% against 3.2% and diarrhea 39.4% against 6.5%.[1]
In the diabetes trial, diarrhea affected 36%, decreased appetite 29%, nausea 23%, vomiting 14% and hypoglycemia 10% (8% with placebo).[8]
Against dulaglutide, the diabetes trial reported more gastrointestinal adverse events with mazdutide.[2]
Discontinuations
In GLORY-1, adverse events led to discontinuation in 1.5% on 4 mg, 0.5% on 6 mg and 1.0% on placebo.[7]
In the higher-dose phase 3 trial, 2.9% on mazdutide stopped because of adverse events, against 0% on placebo.[1]
In the US phase 2 trial, 20% of those on 16 mg stopped for adverse events, mainly gastrointestinal.[5]
Early safety
The phase 1b study reported no discontinuation for safety reasons and no serious adverse event.[3]
Three participants receiving the drug had mild, asymptomatic cardiac disorders on electrocardiogram in that study.[3]
Common questions
What are the side effects of Mazdutide?
Studies we summarise reported vomiting, nausea, diarrhea, gastrointestinal events, gastrointestinal events and decreased appetite. The table on this page gives how often each happened and links each source.
What side effects do people who use Mazdutide report?
In the 21 Reddit threads we read (11 Oct 2026), people most often described nausea (2 people), acid reflux or heartburn (1 person), tiredness or lethargy (1 person). These are unverified personal reports, often from products of unknown purity, and the counts are not rates.
Is Mazdutide safe?
Its safety has not been established by an FDA review. Mazdutide is investigational and not approved for any use. Research-chemical products are not checked for purity or dose.
What are mazdutide's side effects?
Gastrointestinal events were the most common, and mostly mild to moderate in severity in the trials.[7]
More on Mazdutide
Sources
- 1Treatment With 9-mg Mazdutide for Weight Reduction in Chinese Adults With Obesity: The GLORY-2 Randomized Clinical Trial.JAMA · 2026PMID 42251595Accessed 2 Oct 2026
- 2Mazdutide versus dulaglutide in Chinese adults with type 2 diabetes.Nature · 2026PMID 41407860Accessed 2 Oct 2026
- 3IBI362 (LY3305677), a weekly-dose GLP-1 and glucagon receptor dual agonist, in Chinese adults with overweight or obesity: A randomised, placebo-controlled, multiple ascending dose phase 1b study.EClinicalMedicine · 2021PMID 34430840Accessed 2 Oct 2026
- 4Efficacy and safety of Mazdutide on weight loss among diabetic and non-diabetic patients: a systematic review and meta-analysis of randomized controlled trials.Frontiers in endocrinology · 2024PMID 38440786Accessed 2 Oct 2026
- 5Efficacy and safety of mazdutide in adults with obesity or overweight: a US-based, multicentre, phase 2, randomised, placebo-controlled clinical trial.The lancet. Diabetes & endocrinology · 2026PMID 42628555Accessed 2 Oct 2026
- 6Mazdutide versus placebo in Chinese adults with type 2 diabetes.Nature · 2026PMID 41407859Accessed 2 Oct 2026
- 7Once-Weekly Mazdutide in Chinese Adults with Obesity or Overweight.The New England journal of medicine · 2025PMID 40421736Accessed 2 Oct 2026
- 8Efficacy and Safety of Mazdutide in Chinese Patients With Type 2 Diabetes: A Randomized, Double-Blind, Placebo-Controlled Phase 2 Trial.Diabetes care · 2024PMID 37943529Accessed 2 Oct 2026
- 9A phase 2 randomised controlled trial of mazdutide in Chinese overweight adults or adults with obesity.Nature communications · 2023PMID 38092790Accessed 2 Oct 2026
- 10Reddit thread in r/Retatrutide (user reports, unverified)Reddit, via the Arctic Shift archive · 2025reddit.comAccessed 11 Oct 2026
- 11Reddit thread in r/Peptides (user reports, unverified)Reddit, via the Arctic Shift archive · 2024reddit.comAccessed 11 Oct 2026
- 12Reddit thread in r/Retatrutide (user reports, unverified)Reddit, via the Arctic Shift archive · 2026reddit.comAccessed 11 Oct 2026
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