Mounjaro vs Ozempic on Your CGM: the Head-to-Head Nobody Has Run

"Which one gives steadier blood sugar, Mounjaro or Ozempic?" It's one of the most common questions in this space, and it deserves an honest answer instead of a confident guess. Here's what the CGM evidence shows, and the gap sitting right in the middle of it.

The two drugs, briefly

Ozempic (and Wegovy) is semaglutide, a GLP-1 receptor agonist that activates one gut-hormone pathway. Mounjaro (and Zepbound) is tirzepatide, a dual agonist that activates two: GLP-1 and GIP. The theory is that hitting both pathways could do more. The open question is whether "more weight loss" also means "steadier glucose on a CGM," and that's where the evidence thins out.

What we know about tirzepatide on CGM

Tirzepatide has strong CGM data against insulin. In the SURPASS-3 CGM substudy, people with type 2 diabetes on once-weekly tirzepatide reached time in range well above the 70% target and clearly beat once-daily insulin degludec, with minimal time below range (Battelino 2022). Real-world data echoes it: in older patients, tirzepatide raised time in range from 53% to 79% and cut time above range from 46% to 20% (Omura 2024). Those are impressive numbers.

The gap: it's never been tested against a GLP-1 on CGM

Here's the catch. Every one of those tirzepatide CGM studies used insulin as the comparator, not a GLP-1 like semaglutide. No adequately powered trial has put tirzepatide head-to-head against a GLP-1 receptor agonist using CGM metrics. So while tirzepatide clearly beats insulin on time in range, the question people actually mean, does adding GIP buy you steadier glucose than a GLP-1 alone, has no trial answer yet (Battelino 2022). Anyone naming a definitive CGM winner between Mounjaro and Ozempic is filling that gap with opinion.

What the GLP-1 comparisons that do exist show

Among the GLP-1s themselves, the once-weekly agents look broadly similar on CGM. Semaglutide and dulaglutide produce comparable glucose profiles, with semaglutide showing a small edge on some excursion metrics (Kurozumi 2023). Differences between the modern agents tend to be modest, which is a useful reality check when the marketing suggests a chasm.

So how should you actually compare them?

Since the definitive trial doesn't exist, the practical answer is the one Joslin would recognize: measure it on yourself. If you have a CGM, your own before-and-after profile on a given drug tells you more about your decision than any cross-trial guess. Watch your time in range, your post-meal peaks, and your coefficient of variation. That's real-world, single-person evidence, clearly labeled as such, and for your own choice it may be the most honest data available.

Tirzepatide has excellent CGM numbers against insulin, and both drug families flatten post-meal glucose. But the head-to-head that would crown a "steadiest glucose" winner between Mounjaro and Ozempic hasn't been run. Treat any confident ranking with suspicion, and if you're wearing a sensor, let your own curve settle it.