Tirzepatide users stay on treatment longer than semaglutide users

All three studies used real-world records rather than random assignment. The first was a US claims and lab study of adults with type 2 diabetes who started tirzepatide or semaglutide between May 2022 and May 2023. Researchers matched 10,702 patient pairs who had not used a GLP-1 medicine, a drug that acts through a gut hormone involved in blood sugar and appetite, in the prior six months and 5,577 patient pairs who had, then compared adherence and persistence over 12 months ¹. The second used a federated dataset of 135,349 people taking semaglutide or tirzepatide products. It grouped people by one-year weight change: super responders lost more than 15 percent, moderate responders lost 5 to 15 percent, minimal responders lost less than 5 percent, and some regained weight ². The third was a small retrospective study of 23 adults with bipolar disorder who were already taking lithium and started tirzepatide. It checked creatinine, a kidney function marker, and lithium levels at 12 weeks, and followed 20 people through 12 months ³.

In routine US care, people starting tirzepatide stayed on treatment more than people starting semaglutide. Among adults who had not used a GLP-1 medicine in the prior six months, 60 percent of tirzepatide starters had good adherence over 12 months, compared with 45 percent of semaglutide starters. Among people who had already used a GLP-1 medicine, the gap was similar: 66 percent versus 48 percent ¹. Good adherence meant having the medicine on hand at least 80 percent of days. The study also measured persistence, which meant no gap of 45 days or more ¹. This was a type 2 diabetes population, not a weight-management-only group, and the records reflect real prescription patterns rather than a trial with close follow-up ¹.

Zepbound users in this dataset were the most likely to hit a large weight-loss goal. The study grouped 135,349 people by one-year weight change. Ozempic, Wegovy, Mounjaro, and Zepbound had similar moderate responder shares, from 40 to 42 percent. Super responders, people who lost more than 15 percent of body weight, made up 34 percent of Zepbound users, 26 percent of Wegovy users, 24 percent of Mounjaro users, and 10 percent of Ozempic users ². The difference was not that most people failed on one product. It was in the extremes, especially the share losing more than 15 percent. Super responders were also more likely to be younger, female, and white in this dataset. The average age was 51 among super responders versus 55 in people with minimal or moderate response. Women made up 80 percent of super responders versus 58 to 65 percent in the comparison groups ². This is an observational pattern, not proof of cause.

A small bipolar disorder study found no early kidney function change among people taking tirzepatide with lithium, but it did show a need for lithium monitoring. Researchers followed 23 adults for 12 weeks. Creatinine, a kidney function marker, changed by minus 3 micromoles per liter, and a standard kidney filtration estimate rose by 2.6 points. Neither change was statistically meaningful ³. Lithium levels rose slightly, by 0.08 millimoles per liter, which was statistically significant. Two people had lithium levels above 1.2 millimoles per liter, and one developed symptoms that a clinician attributed to lithium toxicity and stopped tirzepatide. No acute kidney injury could be confirmed from available records ³. At 12 months, among 20 people still on treatment, average weight fell by 17.7 percent, creatinine fell by 12 micromoles per liter, and the kidney estimate adjusted for body size rose by 13 points. An estimate not adjusted for body size rose by only 4.5 points ³. The authors caution that creatinine-based kidney estimates can shift during major weight loss, and those shifts do not establish kidney benefit or exclude kidney injury ³.

The real-world findings sit next to trial evidence that tirzepatide produces large weight losses and strong blood sugar control. A network meta-analysis, an analysis that pools evidence from multiple randomized trials, estimated that tirzepatide 15 mg produced a mean weight reduction of about 17.97 percentage points versus placebo, the largest among incretin-based medicines, drugs that mimic gut hormones after a meal, studied ⁴. A UK digital health cohort found mean weight loss of 13.5 percent at six months and 17.4 percent at 12 months ⁵. In type 2 diabetes, a phase 3 monotherapy trial in China found HbA1c, a three-month average of blood sugar, fell about 2.1 percentage points across tirzepatide arms at week 40, while placebo showed no change ⁶. Head-to-head trial data also found tirzepatide beat semaglutide by about 4.28 percentage points more weight loss, though serious adverse events were higher with tirzepatide ⁷. The new adherence data add a practical point: a medicine works only if people keep taking it, and the US claims study suggests tirzepatide may hold an adherence advantage in routine care ¹.

The US claims study did not report its cost-per-responder results in the available abstract, so the cost side of the comparison remains unknown here ¹. The super-responder study cannot tell us why Zepbound had a higher share than Mounjaro. Different prescribing habits, starting doses, or patient populations could contribute, and the dataset does not assign a cause ². The lithium cohort is small, with 23 people, and the authors caution that kidney function estimates during major weight loss cannot establish benefit or exclude injury ³.