Weight management

Which GLP-1 Is Better: Semaglutide, Tirzepatide or Retatrutide?

Every Amino editorial · 29 October 2026 · 4 min read

Tirzepatide led the direct weight-loss comparison, but newer semaglutide options and retatrutide research make the full answer more interesting.

Three medical pens beside a measuring tape and notebook — Editorial illustration

The short answer

For average weight loss in the best-known direct comparison, tirzepatide outperformed the semaglutide regimen studied. That does not make it the best choice for every person—or prove that it outperforms every semaglutide option now available. Retatrutide is an exciting research candidate, but it remains investigational rather than an approved alternative.

The useful question is: better for which goal, with which evidence, and for whom? This comparison reflects information checked on 29 October 2026. It explains clinical research, not how to use products sold for laboratory research.

What the direct trial showed

SURMOUNT-5 randomly assigned 751 adults with obesity, without type 2 diabetes, to tirzepatide or semaglutide for 72 weeks. Mean weight reduction was 20.2% with tirzepatide and 13.7% with semaglutide. Tirzepatide also produced a larger average waist reduction. [1]

That is a 6.5-percentage-point difference in this trial—not a promise about an individual result. The study was open-label, meaning participants and investigators knew the assigned treatment, and was funded by Lilly. Gastrointestinal effects were the most common adverse events in both groups. [1]

The conclusion is strong and specific: tirzepatide achieved greater average weight reduction than the semaglutide regimen used in that population and study period.

The 2026 update older comparisons miss

SURMOUNT-5 compared semaglutide up to 2.4 mg. In March 2026, the FDA approved a higher-strength semaglutide product, Wegovy HD, for eligible adults. Mentioning the study strengths identifies the evidence; it is not an instruction to change treatment. [1,2]

In the separate STEP UP trial, published results showed average weight changes of −18.7% with the higher-strength semaglutide arm and −15.6% with the 2.4 mg arm at 72 weeks. Gastrointestinal events and altered skin sensation were more frequent in the higher-strength group. [3]

Those results expand the semaglutide discussion. They do not create a new head-to-head comparison with tirzepatide: different trials can enrol different people, use different analysis methods and have different treatment discontinuation patterns. Comparing isolated percentages as though the participants were interchangeable would oversimplify the science.

Why semaglutide still has a strong case

Weight is one outcome. Cardiovascular outcomes can be especially relevant for someone with established cardiovascular disease.

In SELECT, semaglutide was studied in 17,604 adults with overweight or obesity and pre-existing cardiovascular disease, without diabetes. The primary cardiovascular outcome occurred in 6.5% of the semaglutide group and 8.0% of the placebo group, corresponding to a hazard ratio of 0.80. That is evidence for a defined high-risk population, not a claim that every user receives the same benefit. [4]

A productive consultation therefore includes the person's wider health priorities, previous response, tolerability, other medicines, access and affordability. The highest average weight-loss number cannot settle all those questions.

Where retatrutide fits

Semaglutide activates GLP-1 receptors; tirzepatide acts at GIP and GLP-1 receptors. Retatrutide adds glucagon-receptor activity, making it a triple agonist—not a scientifically distinct “GLP-3” category. [5,6]

Retatrutide's Phase 3 TRIUMPH-1 study was published in 2026. It investigated adults with obesity without diabetes over 80 weeks, with placebo as the comparator. The report described significant weight reduction and outcomes in participants with knee osteoarthritis or obstructive sleep apnea. [7]

This is meaningful progress, but a placebo-controlled study does not establish superiority to tirzepatide or semaglutide. Lilly's October 2026 update still describes retatrutide as investigational and not approved by any regulatory agency. Research-market products should not be treated as the medicines used in those trials. [6]

A clearer way to compare

Bring three questions to a clinician:

What outcome matters most? Weight reduction, glucose management and cardiovascular risk are related but different objectives.
Which evidence matches my situation? Ask about the actual product, relevant medical history and the population studied.
Can I sustain the plan? Discuss tolerability, monitoring, practical access and the broader nutrition and activity plan.

These questions help turn a popular comparison into an individual clinical decision. Local approvals and availability should be checked separately; a US approval is not evidence of approval in Thailand.

Frequently asked questions

Is tirzepatide better than semaglutide?

It produced greater average weight loss in SURMOUNT-5. That finding applies to the regimens studied and does not settle every clinical priority or comparison with newer semaglutide options.

Is retatrutide the strongest choice?

Its trial programme is promising, but it remains investigational. Receptor count is not a ranking system, and separate trials cannot identify a universal winner.

What is the most useful takeaway?

There are increasingly effective research-backed options, and the evidence is becoming more detailed. Use that detail to ask better questions rather than selecting a treatment from a headline percentage.

Keep exploring

Start with what peptides are, or use our research reading guide to understand trial results.

Sources & further reading

For education. Discuss treatment and recovery decisions with a qualified clinician.

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