Does a hazard ratio of 3.67 mean the risk is high?

No. It means the risk was roughly 3.67 times that of the comparator. Absolute incidence was low in both groups, and a ratio without a baseline is uninformative.

Is gastroparesis the same as the usual nausea?

No. Nausea and vomiting are common tolerability effects. Gastroparesis is a rare and serious pathological delay in gastric emptying.

Do all GLP-1 drugs carry the same risks?

No. Comparative work reports meaningful differences between compounds, particularly for pancreatitis signals.

GLP-1 & Incretin Science

GLP-1 Gastrointestinal Safety Signals

JMWritten & reviewed by Jack Muncaster · Founder, UK PeptidesLast reviewed 2026-08-233 cited sources

Gastroparesis is a recognised signal, documented in cohort studies and reflected in label language, with one 2026 analysis reporting a hazard ratio near 3.67 against an active comparator — though absolute incidence was low in both groups. Pancreatitis signals differ markedly between compounds.

Key facts

Best-supported signal: Gastroparesis
Reported hazard ratio: ~3.67 vs bupropion-naltrexone
Absolute incidence: Low in both groups
Also raised: Pancreatitis, bowel obstruction
Compound differences: Signals are not uniform across the class
Comparative study: Ann Intern Med 2026 (PMID 41183330)
State-of-the-art review: Drugs 2026 (PMID 41351656)

Why gastroparesis is the most coherent signal

Gastroparesis means delayed gastric emptying in the pathological sense — severe enough to cause symptoms. These drugs slow gastric emptying by design. A signal that is a more extreme version of the intended pharmacology is far more plausible than one requiring a novel mechanism, and that plausibility is why it moved from reported association into label language relatively quickly.

What the comparative data shows

A 2026 claims-based analysis reported elevated gastroparesis risk for semaglutide and liraglutide users against users of bupropion-naltrexone, with a hazard ratio around 3.67. Two features of that design matter. The comparator is another weight-management drug rather than no treatment, which controls for the population being treated for the same indication. And absolute incidence was low in both arms — a hazard ratio of 3.67 on a rare event is still a rare event.

Relative and absolute are different questions

This is the most common misreading in safety reporting. A hazard ratio describes how much more likely an outcome is in one group than another; it says nothing about how likely it is in either. Tripling a risk of one in ten thousand produces three in ten thousand. Tripling a risk of one in ten produces a serious clinical problem. Reporting the ratio without the baseline is uninformative at best.

The compounds are not interchangeable on safety

Crisafulli and colleagues reported a comparative gastrointestinal safety assessment of dulaglutide, semaglutide and tirzepatide in Annals of Internal Medicine in January 2026. Comparative work of that kind is more useful than any single-compound analysis, because the relevant clinical question is rarely whether a class carries a risk but which member carries less of it. Pancreatitis signals in particular have differed substantially between compounds in disproportionality analyses.

Why the tolerability data and the safety data are different things

Nausea, vomiting and diarrhoea are extremely common across every compound in this class and appear in every trial's adverse-event table. Gastroparesis, pancreatitis and bowel obstruction are rare and serious. Conflating the two — treating common discomfort and rare harm as one category of gastrointestinal effects — obscures both. The first affects whether people can stay on treatment; the second affects whether they should.

Where the evidence stands

A 2026 state-of-the-art review in Drugs summarises safety and tolerability across the class. The honest position is that gastroparesis is well supported and mechanistically coherent, pancreatitis signals are real but uneven between compounds and heavily dependent on analysis method, and absolute risks for the serious outcomes remain low against a very large exposed population.

Extended research context

The GLP-1 & Incretin Science deep dive

Deep dive: the two routes to a bigger effect

Every compound trying to beat GLP-1 alone has taken one of two routes. The first adds more receptors from the same hormone family — GIP in tirzepatide, GIP and glucagon in retatrutide. The second adds a non-incretin satiety hormone, which in practice means amylin: CagriSema combines cagrilintide with semaglutide, and amycretin engages both receptors from one molecule. Both routes work, because they recruit signalling pathways that do not fully overlap. Neither has escaped the constraint that binds all of them, which is that gastrointestinal tolerability worsens as effect size grows.

Deep dive: why a percentage is not a result

The most-quoted numbers in this field are the least comparable. REDEFINE 1 reported 22.7% and 20.4% for the same compound in the same trial — the first among participants who adhered to treatment, the second across everyone randomised. TRIUMPH-1 reported 28.3% in an uncomplicated obesity population while TRIUMPH-3 reported up to 22.6% in adults with established cardiovascular disease, using the same compound. Before any two figures can be compared they have to match on estimand, population, duration, comparator and whether the number is placebo-adjusted. Most published comparisons match on none of them.

Deep dive: what happens after the trial stops

Every headline figure describes weight while treatment continues. The STEP-1 extension found that a year after semaglutide was stopped, participants had given back roughly two-thirds of what they lost, moving from 17.3% mean reduction to a net 5.6% — though average weight remained below baseline and nearly half stayed at least 5% down. Meta-analysis puts regain at around 0.8 kg per month. This is why maintenance studies such as TRIUMPH-6 matter more to the field's future than another two points of peak reduction.

Research applications

▸Comparing incretin and amylin compounds on a like-for-like basis
▸Interpreting estimands, thresholds and placebo-adjusted figures in trial reports
▸Tracking the obesity pipeline across sponsors and jurisdictions
▸Understanding receptor pharmacology behind GLP-1, GIP, glucagon and amylin
▸Distinguishing licensed medicines from investigational compounds

Handling checklist

✓Identify which estimand a quoted percentage comes from before citing it
✓Check the trial population and baseline BMI against the comparison you are making
✓Confirm the duration and whether the reduction curve had plateaued
✓Read discontinuation rates alongside efficacy figures
✓Verify every NCT identifier against ClinicalTrials.gov rather than secondary reporting

Common research-handling mistakes

Learnt from thousands of researcher orders across our UK labs.

✗ Comparing headline percentages across different trials

Fix: Population, duration, estimand and comparator all differ; the numbers are not interchangeable.

✗ Quoting the larger of two figures from the same trial

Fix: Name the estimand. Efficacy and treatment-policy answer different questions.

✗ Treating peak reduction as a durable outcome

Fix: Substantial regain follows cessation across the class; peak figures describe a maintained state.

✗ Assuming an oral route means a weaker mechanism

Fix: Route and receptor count are independent. Orforglipron is weaker because it hits one receptor, not because it is a tablet.

✗ Reading investigational compounds as available treatments

Fix: Most of this pipeline holds no authorisation anywhere; mazdutide is approved only in China.

Continue researching

Peer-reviewed guides, comparators and matched reference materials.

Frequently asked questions

Does a hazard ratio of 3.67 mean the risk is high?: No. It means the risk was roughly 3.67 times that of the comparator. Absolute incidence was low in both groups, and a ratio without a baseline is uninformative.
Is gastroparesis the same as the usual nausea?: No. Nausea and vomiting are common tolerability effects. Gastroparesis is a rare and serious pathological delay in gastric emptying.
Do all GLP-1 drugs carry the same risks?: No. Comparative work reports meaningful differences between compounds, particularly for pancreatitis signals.

Primary sources & clinical trials

Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.

Written and reviewed by

Jack Muncaster · Founder, UK Peptides

Jack founded UK Peptides in Manchester after repeatedly receiving research compounds with missing or recycled paperwork. He is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate.

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