CATEGORY: METABOLIC & BLOOD SUGAR
Adults with prediabetes—blood sugar that is higher than normal but not yet in the diabetes range—were about 93% less likely to develop type 2 diabetes over roughly three years while taking the weekly medication tirzepatide than similar adults given a placebo, in a large randomized trial. Just 1.3% of participants taking the medication progressed to diabetes during treatment, compared with 13.3% of those on placebo.1
A Weekly Injection That Mimics Two Gut Hormones
Tirzepatide is a prescription medication, given as a once-weekly injection, that mimics two natural gut hormones—chemical messengers your body releases after eating that help control appetite and blood sugar. The trial, called SURMOUNT-1, enrolled adults with obesity or with overweight plus a weight-related condition; this report focused on the 1,032 participants who also had prediabetes when the study began. Prediabetes is both common and consequential: a meaningful share of people who have it go on to develop type 2 diabetes, a leading driver of heart disease, kidney disease, and vision loss.
176 Weeks, Three Doses, and a Placebo
Participants were randomly assigned to one of three tirzepatide doses or to a placebo, and neither they nor their doctors knew who was receiving which—the design that best isolates a medication’s true effect. Everyone also received general healthy-eating and physical-activity counseling. Over 176 weeks—nearly three and a half years—regular blood tests tracked each person’s blood sugar, which is how new cases of type 2 diabetes were identified. Because treatment was assigned by chance, the trial could measure the medication’s effect directly: a 93% lower risk of progressing to type 2 diabetes.1
What 17 Weeks Off the Drug Undid
Participants on the medication also lost considerably more weight—roughly 12% to 20% of body weight depending on dose, versus about 1% with placebo. After the main phase, the trial included a 17-week period in which everyone stopped treatment. Some of the benefit eroded: the share of medication-group participants who had developed diabetes rose to 2.4%, and some weight was regained—a sign the medication manages these conditions while it is being taken rather than curing them. In the placebo group, 13.7% had type 2 diabetes at that same point.1
Digestive Side Effects, and Who Funded the Trial
Side effects were mostly digestive—nausea, diarrhea, constipation—usually mild to moderate and concentrated in the early weeks when doses were being increased. The trial was funded by Eli Lilly, the company that makes tirzepatide, a standard arrangement in drug research that is still worth knowing about. The results apply to the population studied—adults with prediabetes plus obesity or overweight—not to everyone with slightly elevated blood sugar.
Eight GLP-1 Trials Found Fewer Progressions Too
Tirzepatide is not the only medication of this kind tested this way. A 2024 review pooling eight randomized trials of GLP-1 drugs—closely related medicines that act on one of the same gut hormones—in adults with prediabetes and excess weight found far fewer people progressed to type 2 diabetes on the drugs than on placebo, and many more returned to normal blood sugar. The reviewers also flagged side effects as a meaningful drawback.2
Key Takeaways
- In a randomized trial lasting nearly three and a half years, 1.3% of adults with prediabetes and obesity or overweight taking weekly tirzepatide developed type 2 diabetes, versus 13.3% on placebo—a 93% lower risk.
- The medication groups also lost roughly 12% to 20% of body weight, compared with about 1% with placebo.
- After a 17-week stop in treatment, some diabetes cases emerged and some weight returned, suggesting the benefits depend on continued use.
- Side effects were mostly digestive, and the trial was funded by the medication’s manufacturer.
References
- Jastreboff AM, le Roux CW, Stefanski A, et al. Tirzepatide for Obesity Treatment and Diabetes Prevention. New England Journal of Medicine. 2025;392(10):958–971. link
- Yanto TA, Vatvani AD, Hariyanto TI, et al. Glucagon-like peptide-1 receptor agonist and new-onset diabetes in overweight/obese individuals with prediabetes: a systematic review and meta-analysis of randomized trials. Diabetes & Metabolic Syndrome: Clinical Research & Reviews. 2024;18(6):103069. link.