Lilly registers a phase 1 gastric emptying study of tirzepatide in type 1 diabetes

Eli Lilly has posted a new phase 1 clinical trial, NCT07803744, that will study how tirzepatide affects gastric emptying in adults with type 1 diabetes who are also overweight ^[1]. The study was first listed on ClinicalTrials.gov on September 4, 2026, and its status is "not yet recruiting," meaning no participants have been enrolled yet ^[1].

According to the registration, the trial is a single-dose, blinded, randomized study ^[1]. Researchers plan to use oral acetaminophen as a marker to track how quickly food and liquid leave the stomach, a common method for measuring gastric emptying ^[1]. The listing does not yet include a target enrollment number, start date, or expected completion date ^[1].

This phase 1 study is separate from two larger, ongoing phase 3 trials known as SURPASS-T1D, which are also testing tirzepatide in people with type 1 diabetes ^[1][2]. One of those phase 3 trials, NCT06914895, is already listed in the ClinicalTrials.gov database ^[2]. The sources provided do not give enrollment figures, results, or completion dates for the SURPASS-T1D trials.

Tirzepatide is the active ingredient in Mounjaro and Zepbound, both approved for type 2 diabetes and weight management, respectively. It is not currently approved by the FDA for use in type 1 diabetes ^[1]. The new gastric emptying study is an early, small-scale trial meant to gather basic physiological data, not a step toward near-term approval.

Why it matters for patients

Gastric emptying speed matters for people with type 1 diabetes because it affects how insulin doses line up with food digestion. If a GLP-1 drug like tirzepatide slows stomach emptying, that could change how quickly blood sugar rises after eating, which in turn could affect insulin timing and the risk of low or high blood sugar. This kind of basic data collection is a routine early step drug makers take before deciding whether and how to move a drug into larger trials for a new population.

People with type 1 diabetes who currently use tirzepatide off-label, or who are considering it, should know that this early study does not mean the drug is close to being approved for their condition. Phase 1 studies like this one are designed to answer narrow scientific questions, not to prove a drug works safely for a new patient group. The existence of the larger SURPASS-T1D phase 3 trials suggests Lilly is pursuing a broader research program in type 1 diabetes, but the sources here do not include results, timelines, or safety findings from those trials ^[1][2].

It is not yet known how tirzepatide's effect on gastric emptying might differ in people with type 1 diabetes compared with people with type 2 diabetes or obesity, where the drug is already approved. That is one of the open questions this new study appears designed to help answer.

What happens next

The phase 1 study (NCT07803744) is listed as not yet recruiting as of September 4, 2026, so no participants have started the trial ^[1]. The sources do not specify when recruitment will begin, how many people will take part, or when results might be available. The two SURPASS-T1D phase 3 trials remain ongoing, but the sources here do not provide updated status, enrollment counts, or expected data readouts for those studies ^[1][2]. Readers interested in enrollment criteria or trial sites can check the individual study listings on ClinicalTrials.gov, though the excerpts reviewed for this article did not include those specifics.