Retatrutide Trial Measurements: What Was Assessed and When
Adult retatrutide trials measured weight and glucose-related outcomes at specified study weeks. Those weeks identify when researchers evaluated an endpoint; they do not describe every assessment performed during a trial. Three published studies provide concrete evidence, but their populations, comparisons, and durations differ.
Lilly describes retatrutide as investigational and not FDA-approved, with phase 3 development in type 2 diabetes and obesity.[7]
Measurements by study
The denominator matters: enrollment, the safety population, and the efficacy population are not automatically the same group. The table preserves those distinctions rather than presenting every result as applying to everyone enrolled.
| Study and population | Denominator | Primary endpoint and assessment time | Secondary endpoints and assessment time |
|---|---|---|---|
| Jastreboff et al., 2023; phase 2 adults with obesity, or overweight plus a weight-related condition | 338 adults | Percentage change in body weight from baseline to week 24 | Weight change and weight-loss response proportions at week 48 |
| Rosenstock et al., 2023; phase 2 adults aged 18–75 with type 2 diabetes treated with diet and exercise alone or stable metformin | 281 randomized and included in safety analyses; 275 in efficacy analyses after six unintentionally enrolled participants were excluded | Change in HbA1c from baseline to week 24 | HbA1c change at week 36; body-weight and glucose outcomes at weeks 24 and 36 |
| Bajaj et al., 2026; phase 3 TRANSCEND-T2D-1, adults with type 2 diabetes inadequately controlled by diet and exercise alone | 537 randomized | Change in HbA1c from baseline to week 40 | Key secondary outcome: percentage change in body weight at week 40 |
The table draws on the published papers and their corresponding trial records.[1–6] These are study-specific endpoints, not a shared adult monitoring protocol. The phase 3 diabetes study evaluated monotherapy in its defined population; it was not a study of all patients already receiving insulin.
Assessment weeks and safety observation windows
An endpoint week answers a focused question: how much did the selected outcome change by that point? Safety reporting describes adverse events collected over a defined observation period. Neither alone supplies a complete visit schedule.
For the obesity trial, the secondary weight endpoint was at week 48, whereas the registry counted adverse events from baseline through the end of safety follow-up, up to 52 weeks.[2] The phase 2 diabetes registry lists adverse-event collection from baseline through study completion, up to 280 days.[4] The phase 3 registry record checked here did not report that safety-collection window. Read the published paper for its safety results rather than treating the missing registry detail as missing monitoring.[5][6]
The obesity paper reported dose-related gastrointestinal events, mostly mild or moderate, and a heart-rate increase that peaked at week 24 before declining.[1] The diabetes papers also reported gastrointestinal events within their respective studies.[3,5] Such observations need their own context; an efficacy endpoint is not a comprehensive safety assessment.
Read changes with their units attached
HbA1c change is commonly expressed in percentage points: the arithmetic difference between baseline and follow-up HbA1c percentages. Percentage body-weight change is relative to baseline weight. These measurements have different units and meanings, even when both results display a percent sign.
The obesity trial included placebo comparisons; the phase 2 diabetes trial included placebo and an active comparator, while TRANSCEND-T2D-1 was placebo-controlled.[1,3,5] Different populations and durations prevent those separate papers from serving as a head-to-head comparison. Their group results also do not produce a reliable individual forecast.
A practical claim-check record
When checking a monitoring claim, record the metric and unit, eligible population and analysis denominator, assessment time, study identity, comparator, and analysis type. For example, a statement about HbA1c at week 40 should identify TRANSCEND-T2D-1, its diet-and-exercise-only diabetes population, the placebo comparison, and the efficacy analysis supporting the statement—not substitute an adverse-event summary.
Check the paper for the reported analysis and the matching registry for endpoint definitions and listed timeframes. An endpoint listing does not establish which laboratory tests occurred at every visit. A prespecified study endpoint cannot generate a personal appointment calendar, and the sources here do not establish routine home monitoring, laboratory panels, or individual action thresholds.
Frequently asked questions
Which measurements were primary endpoints in adult retatrutide trials?
The phase 2 obesity trial used percentage body-weight change at week 24. The phase 2 diabetes trial used HbA1c change at week 24. Phase 3 TRANSCEND-T2D-1 used HbA1c change at week 40.[1–6]
Do trial assessment weeks establish a personal monitoring schedule?
No. They specify when study outcomes were evaluated, not every study visit or an individual care schedule. The registry endpoint listings cannot establish personal appointment intervals or routine laboratory testing.
How did the obesity and diabetes trial populations differ?
The obesity trial enrolled adults with obesity or overweight plus a weight-related condition. The phase 2 diabetes trial enrolled adults with type 2 diabetes using diet and exercise alone or stable metformin. TRANSCEND-T2D-1 studied diabetes inadequately controlled by diet and exercise alone.[1,3,5]
What does a primary endpoint leave out about safety?
A primary efficacy endpoint does not summarize adverse-event types, severity, discontinuations, or the safety observation window. Those require separate safety results. For example, the obesity registry lists safety follow-up extending up to 52 weeks.[2]
Are percentages of HbA1c change and weight change interchangeable?
No. HbA1c change is expressed in percentage points when subtracting follow-up and baseline HbA1c values. Percentage weight change expresses the change relative to baseline body weight. They cannot be compared as equivalent quantities.
How can I verify a retatrutide monitoring claim?
Match the claim to a paper and its trial record. Check the metric, unit, population, denominator, timepoint, comparator, and analysis type. Then distinguish an efficacy assessment from adverse-event reporting and from any proposed personal monitoring schedule.
References
- Jastreboff AM, et al. (2023). Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine. PubMed: 37366315.
- ClinicalTrials.gov. NCT04881760: Phase 2 retatrutide study in adults with obesity or overweight. Completed; actual enrollment 338. Record updated September 13, 2023. Trial record.
- Rosenstock J, et al. (2023). Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes… (phase 2 trial). The Lancet. PubMed: 37385280.
- ClinicalTrials.gov. NCT04867785: Phase 2 retatrutide study in type 2 diabetes. Completed; actual enrollment 281. Record updated July 3, 2023. Trial record.
- Bajaj HS, et al. (2026). Efficacy and safety of retatrutide… in people with type 2 diabetes… (TRANSCEND-T2D-1) (phase 3 trial). The Lancet. PubMed: 42250575.
- ClinicalTrials.gov. NCT06354660: TRANSCEND-T2D-1, phase 3 retatrutide study in type 2 diabetes. Completed; actual enrollment 537. Record updated March 5, 2026. Trial record.
- Eli Lilly and Company. (September 2026). What to know about retatrutide. Lilly development-status information.
Sources checked October 13, 2026.
