Retatrutide Results: What Users Are Reporting in 2026

Written by NorthPeptide Research Team

For laboratory and research use only. Not for human consumption.

Why Everyone Is Talking About Retatrutide

If you follow peptide research, you have probably seen the word “retatrutide” everywhere in 2026. There is a good reason for that. In clinical trials, this peptide produced weight loss numbers that made researchers do a double-take. We are talking about up to 24.2% body weight lost in 48 weeks at the highest dose.

That is roughly 58 pounds for someone who started at 240. In less than a year.

But headlines only tell part of the story. What does the actual timeline look like? When do results start showing? Do they slow down? And how does retatrutide stack up against tirzepatide and semaglutide?

This article breaks it all down using published clinical trial data. If you want the full deep dive on how retatrutide works at the molecular level, check out our complete retatrutide research guide.

Quick Recap: What Is Retatrutide?

Retatrutide (also called LY3437943) is a triple receptor agonist. That is a fancy way of saying it activates three different switches in your body at the same time:

• GLP-1 receptor — Tells your brain you are full. Slows down how fast your stomach empties. This is the same receptor that semaglutide (Ozempic) targets.
• GIP receptor — Works alongside GLP-1 to control blood sugar and how your body handles fat. Tirzepatide (Mounjaro) hits this one plus GLP-1.
• Glucagon receptor — This is the new one. Glucagon tells your liver to burn stored energy. It also ramps up your metabolism so you burn more calories even at rest.

Think of it this way: semaglutide flips one switch. Tirzepatide flips two. Retatrutide flips all three. That third switch — the glucagon receptor — is what researchers believe makes the difference in the results (PMC12026077).

What the Clinical Trials Actually Showed

The big numbers come from a Phase 2 trial published in the New England Journal of Medicine in 2023. This was a proper, randomized, double-blind, placebo-controlled study — the gold standard in medical research. Here is what happened at each dose level:

At 24 Weeks (About 6 Months)

• Placebo: -1.6% body weight
• 1 mg dose: -7.2%
• 4 mg dose: -12.9%
• 8 mg dose: -17.3%
• 12 mg dose: -17.5%

So even the lowest dose produced meaningful weight loss. And the 8 mg and 12 mg groups were already showing numbers that match what semaglutide produces at its peak — and this was only the halfway point.

At 48 Weeks (About 11 Months)

• Placebo: -2.1%
• 1 mg dose: -8.7%
• 4 mg dose: -17.1%
• 8 mg dose: -22.8%
• 12 mg dose: -24.2%

At the 12 mg dose, that is an average weight loss of about 57.8 pounds. Some participants lost even more. In the highest dose group, 100% of participants lost at least 5% of their body weight, and the majority lost over 20% (PMID: 37366315).

Phase 3 Results (TRIUMPH-4, 2025)

The more recent Phase 3 trial confirmed the Phase 2 findings with even larger groups of people:

• 9 mg dose: -20.0% (about 50.5 lbs lost)
• 12 mg dose: -23.7% (about 60.0 lbs lost)
• Placebo: -4.6%

These are among the highest weight loss numbers ever seen in a clinical trial for any peptide or medication.

The Timeline: What to Expect and When

Based on the trial data, here is a realistic timeline of what researchers observed at each stage. Keep in mind these are averages from the 8-12 mg dose groups.

Weeks 1-4: The Slow Start

Most of the early weeks involve dose titration — starting low and gradually increasing. Weight loss during this period is modest, typically 2-4% of body weight. The main thing happening is your appetite starting to decrease. Many trial participants reported eating less without really trying.

Weeks 4-8: Things Pick Up

This is when the weight loss curve gets steeper. By week 8, participants in the higher dose groups were seeing 6-10% body weight reduction. The appetite suppression becomes more noticeable. Food just does not call to you the way it used to.

Weeks 8-12: The Sweet Spot

Weight loss is in full swing. The 8 mg and 12 mg groups were hitting 10-14% by this point. This is also when the glucagon receptor kicks into higher gear, boosting how many calories the body burns at rest. Researchers believe this is why retatrutide pulls ahead of semaglutide during this window.

Weeks 12-24: Steady Progress

The rate of loss stays strong. By week 24, the 12 mg group averaged -17.5%. The weight loss is consistent, not dramatic week-to-week, but it adds up fast. Many participants reported that their relationship with food had fundamentally changed.

Weeks 24-48: The Final Push

Weight loss continues but the pace gradually slows. This is normal — the closer you get to a lower body weight, the fewer calories your body needs, so the deficit shrinks. Still, the 12 mg group went from -17.5% at week 24 to -24.2% at week 48. That is another 6.7 percentage points of body weight lost in the second half.

The Plateau Question: Does the Weight Loss Stop?

Every weight loss approach hits a plateau eventually. Retatrutide is no exception. But the data suggests something interesting: the plateau comes later and at a lower weight compared to other peptides.

With semaglutide, weight loss typically plateaus around week 60-68. With retatrutide, the trial data at 48 weeks still showed an active downward trend in the highest dose groups — the participants had not fully plateaued yet. This suggests the plateau may come later, possibly around week 60-80 based on the trajectory (PMC11940170).

Why? Researchers think the glucagon receptor activation is the key. While GLP-1 mainly reduces how much you eat, glucagon increases how much energy your body burns. This dual effect — eating less and burning more — may help push through plateaus that other peptides cannot.

Side Effects: What People Report

Let us be straight about this. Retatrutide causes side effects, and almost all of them are gut-related. Here is what the trial data showed:

• Nausea: Up to 60% at the 12 mg dose (most common side effect)
• Diarrhea: 15-33%
• Vomiting: 21-26%
• Constipation: 11-16%
• Decreased appetite: Common, but most people see this as the point

The important details:

• Side effects were dose-dependent — lower doses meant fewer problems
• Starting at 2 mg instead of 4 mg reduced early nausea significantly
• Most side effects were mild to moderate and improved over time
• Very few participants dropped out because of side effects

Compared to tirzepatide and semaglutide, the GI side effect profile is similar in type but slightly higher in frequency at the top dose. This makes sense — three receptor pathways all affect the gut in some way (PMC12026077).

Retatrutide vs Tirzepatide vs Semaglutide: The Comparison

This is what everyone wants to know. Here is a side-by-side using data from published clinical trials:

Metric	Semaglutide 2.4 mg	Tirzepatide 15 mg	Retatrutide 12 mg
Receptors Targeted	GLP-1 only	GLP-1 + GIP	GLP-1 + GIP + Glucagon
Weight Loss at ~24 Weeks	~10-12%	~13-15%	~17.5%
Weight Loss at ~48 Weeks	~15%	~20-22.5%	~24.2%
Dosing Frequency	Once weekly	Once weekly	Once weekly
Nausea Rate	~44%	~25-33%	~45-60%
FDA Approved?	Yes (Wegovy)	Yes (Zepbound)	Not yet (Phase 3)
Available as Research Peptide?	Yes	Yes	Yes

The takeaway: Retatrutide produces the most weight loss of the three, but it is also the newest and has the least long-term data. Semaglutide has the most real-world experience behind it. Tirzepatide sits in the middle — proven results with good long-term data. A head-to-head comparison of semaglutide and tirzepatide in the SURMOUNT-5 trial showed tirzepatide produced -20.2% weight loss versus -13.7% for semaglutide at 72 weeks (PMC11231910).

Why Results Vary From Person to Person

Clinical trial averages are useful, but individual results can be very different. Here are the main factors that affect outcomes:

• Starting weight: People with more weight to lose tend to lose a higher percentage early on. The body has more stored energy to tap into.
• Dose: The difference between 4 mg and 12 mg in the trial was massive — 17.1% vs 24.2% at 48 weeks. Dose matters.
• Diet: Peptides reduce appetite, but what you eat still matters. Participants who combined retatrutide with a calorie-controlled diet generally did better.
• Activity level: Exercise was not required in the trials, but physical activity helps preserve muscle mass during rapid weight loss.
• Individual metabolism: Genetics, age, hormonal status, and metabolic health all play a role. Two people on the same dose can have different outcomes.
• Consistency: Missing doses disrupts the steady-state levels of the peptide. Consistent weekly dosing produced the best results in trials.

Beyond Weight Loss: Liver Fat Results

One of the most exciting findings from the retatrutide trials had nothing to do with the scale. In a sub-study looking at fatty liver disease (MASLD), retatrutide showed remarkable results. At the 12 mg dose, 86% of participants achieved normal liver fat levels, and average liver fat decreased by 82.4%. These results were published in Nature Medicine and represent some of the most dramatic improvements in liver health ever seen in a clinical trial (PMC11271400).

Dosing Protocols Used in Research

The Phase 2 trial used a titration approach, meaning participants started at a lower dose and gradually increased:

• Starting dose: 2 mg or 4 mg weekly (lower start = fewer GI side effects)
• Escalation: Dose increased every 4 weeks until reaching the target dose
• Target doses tested: 1 mg, 4 mg, 8 mg, and 12 mg weekly
• Administration: Subcutaneous injection, once per week

The trial found that starting at 2 mg (instead of jumping straight to 4 mg) meaningfully reduced early nausea and vomiting. This “go low and slow” approach is now standard in most research protocols.

Where to Get Research-Grade Retatrutide

Retatrutide is not yet approved as a prescription medication — it is still in Phase 3 clinical trials. However, it is available as a research-grade peptide from suppliers who specialize in high-purity compounds for laboratory use.

If you are sourcing retatrutide for research, purity matters enormously. Low-purity peptides can produce inconsistent results and may contain harmful impurities. Look for suppliers that provide third-party Certificates of Analysis (COAs) showing purity of 98% or higher.

NorthPeptide offers research-grade retatrutide with verified purity and full COA documentation. We also carry tirzepatide and semaglutide for researchers who want to compare compounds.

Summary of Key Research References

Study	Key Finding	Reference
Retatrutide Phase 2 obesity trial (NEJM, 2023)	Up to 24.2% weight loss at 48 weeks (12 mg dose)	PMID: 37366315
Retatrutide systematic review and meta-analysis (2024)	Confirmed efficacy and safety across 3 RCTs with 878 patients	PMC12026077
Retatrutide for MASLD (Nature Medicine, 2024)	86% achieved normal liver fat at 12 mg; 82% reduction in liver fat	PMC11271400
Semaglutide vs tirzepatide comparison (JAMA, 2024)	Tirzepatide -20.2% vs semaglutide -13.7% at 72 weeks	PMC11231910
GLP-1 agonist weight loss plateau and discontinuation	Weight loss plateau at ~60-68 weeks for semaglutide; regain risk after stopping	PMC11940170
Semaglutide STEP 1 review	14.9% weight loss at 68 weeks with semaglutide 2.4 mg	PMC10092086

For laboratory and research use only. Not for human consumption. This article is for informational purposes and does not constitute medical advice. Always consult a qualified healthcare professional before making any health decisions.