New Ozempic vs Mounjaro Heart Study: What the 6% Difference Really Means

A new Ozempic vs Mounjaro heart study is already making headlines, and some of them are going further than the evidence.

On 29 September 2026, new results from the COMPETE SWITCH CV analysis were presented at the European Association for the Study of Diabetes (EASD) annual meeting. The analysis looked at US adults with type 2 diabetes who were already taking semaglutide, the active ingredient in Ozempic.

It found that people who increased their semaglutide dose from 1 mg to 2 mg had a 6% lower relative risk of death, heart attack or stroke than people who switched to tirzepatide, the medicine sold as Mounjaro.

That is a real finding from a very large dataset. But it was not a randomised head-to-head trial of Ozempic against Mounjaro, and it does not prove that Ozempic is better for your heart.

Evidence note: The figures in this article come from Novo Nordisk’s announcement of an observational analysis of US healthcare records. Novo Nordisk makes Ozempic. The analysis shows an association, not proof of cause and effect, and it involved people with type 2 diabetes, not people using weight-loss medicines for obesity alone. This article is not medical advice. Always speak to an appropriately qualified healthcare professional before making changes to your treatment.

What Happened?

Researchers presented the new cardiovascular results from COMPETE SWITCH CV at the EASD meeting in Milan on 29 September 2026, and Novo Nordisk announced them the same day.

The study looked back at US healthcare records, using the Komodo Health claims database, covering January 2018 to September 2025.

Everyone in the cardiovascular comparison had type 2 diabetes and was already taking semaglutide 1 mg. From there, they took one of two routes in normal clinical care:

• 185,705 people increased their semaglutide dose to 2 mg.
• 23,104 people switched from semaglutide to tirzepatide.

That makes 208,809 people in the cardiovascular comparison.

You may also see a larger figure of 636,525 in some coverage. That is the size of the wider COMPETE SWITCH population of adults with type 2 diabetes, not the number of people in this heart comparison.

COMPETE SWITCH itself is not brand new. Earlier results looking at blood sugar (HbA1c) and weight were presented at the American Diabetes Association meeting in June 2026. What is new is this cardiovascular analysis.

What Did the Study Find?

The researchers looked at major adverse cardiovascular events, often shortened to MACE. In this analysis, MACE meant any of three things: death from any cause, a heart attack, or a stroke.

According to Novo Nordisk, people who increased semaglutide from 1 mg to 2 mg had a statistically significant 6% lower relative risk of these events than people who switched to tirzepatide.

For readers who like the detail, the adjusted hazard ratio was 1.06 for tirzepatide compared with semaglutide (95% confidence interval 1.04 to 1.08; P=0.005).

A smaller group of people, for whom extra HbA1c and/or weight measurements were available, showed a broadly similar result (hazard ratio 1.07; 95% confidence interval 1.01 to 1.13).

The analysis did not look at safety outcomes such as side effects.

Does This Mean Ozempic Is Better for Your Heart Than Mounjaro?

No. This study cannot show that.

This was a retrospective observational study, not a randomised clinical trial. The researchers looked back at what happened to people during their normal care. Nobody was randomly given Ozempic or Mounjaro.

That matters because the decision to increase someone’s semaglutide dose, or switch them to tirzepatide, was made by them and their clinician for their own reasons. The two groups may have been different in ways that affected their heart risk, before treatment even started.

Researchers can adjust the numbers for differences they know about. But they cannot be sure every relevant difference has been accounted for. Novo Nordisk itself lists “residual unmeasured confounding” among the limitations. In plain English, there may be hidden differences between the groups that the statistics could not remove.

So the result shows an association between the two treatment routes and heart outcomes. It does not prove that choosing semaglutide instead of tirzepatide caused the difference.

What Does the 6% Figure Actually Mean?

The 6% is a relative difference. It compares the rate of death, heart attack or stroke in one group with the rate in the other.

It does not mean that someone’s own chance of having a heart attack falls by six percentage points. Novo Nordisk’s announcement does not give the actual event rates in each group, so we cannot turn the 6% into an absolute risk.

The simplest way to put it: during the period studied, the group that increased semaglutide had a modestly lower rate of these combined events than the group that switched to tirzepatide.

Ozempic vs Mounjaro Heart Study: Were They Comparing the Top Doses?

No, and this is easy to miss.

The semaglutide group went from 1 mg to 2 mg. The people switching to tirzepatide started on 2.5 mg or 5 mg and could then increase their dose.

But only around 31% of the people who switched to tirzepatide reached a dose of 10 mg or higher during the follow-up period.

So this should not be read as a clean comparison of Ozempic 2 mg against Mounjaro at its highest dose of 15 mg. Many of the people in the tirzepatide group were on lower doses for much or all of the time studied.

Was This a Wegovy Study?

No.

The study involved adults with type 2 diabetes taking injectable semaglutide at 1 mg and 2 mg, the doses used for diabetes with Ozempic.

Wegovy also contains semaglutide, but it is used for weight management, with a different dosing schedule and licensed use. The results should not simply be applied to someone taking Wegovy for weight loss who does not have diabetes.

For more on Wegovy itself, see our Wegovy UK guide.

How Strong Is This Evidence?

There are real strengths. The cardiovascular comparison included more than 200,000 people, and it reflects treatment in everyday practice rather than the tightly controlled setting of a clinical trial. Real-world studies like this can tell us useful things about how medicines perform outside trials.

But observational studies also have important limits:

• They can find associations, but they cannot show cause and effect as confidently as a well-designed randomised controlled trial.
• Insurance claims databases can miss important clinical information.
• Novo Nordisk notes that claims data may under-represent people with gaps in their insurance cover and underserved groups.
• Safety outcomes were not assessed in this analysis.

What Does This Mean for UK Patients?

This was US data. It is not NHS or UK evidence, and the people in the study were not British patients.

It is still relevant here, because semaglutide and tirzepatide are both widely used by people with type 2 diabetes in the UK. For British readers, it adds another piece to the growing evidence on these two medicines.

It is not a reason for anyone to switch, stop or change either medicine on their own. Treatment decisions depend on much more than one observational analysis, including blood sugar control, weight, side effects, heart history, other health conditions and how someone responds to treatment.

If you take either medicine and have questions about your heart health or your treatment, the right person to talk to is the clinician who prescribes it.

For a plain-English overview of how the two medicines compare more generally, see our guide Mounjaro vs Ozempic UK: Which Weight Loss Injection Works Best?

What Happens Next?

Heart and circulation outcomes are becoming an increasingly important part of how these medicines are judged, and this analysis adds real-world evidence to that picture.

But a retrospective claims analysis cannot settle the question on its own. Randomised cardiovascular outcome trials and further comparative research will give stronger evidence than this type of study alone.

The Bottom Line

The new COMPETE SWITCH CV analysis is interesting because of its size and its real-world setting. It found a modest cardiovascular association favouring people who increased semaglutide rather than switching to tirzepatide.

But it did not randomly compare Ozempic and Mounjaro, and most people who switched to tirzepatide did not reach its higher doses. The result adds to the evidence. It does not settle which medicine offers better protection for the heart.

Frequently Asked Questions

Is Ozempic better for your heart than Mounjaro?

This study does not prove that. It found an association favouring semaglutide in a specific group of US adults with type 2 diabetes, but it was observational rather than randomised.

How much lower was the cardiovascular risk?

The group that increased semaglutide to 2 mg had a 6% lower relative risk of the combined outcome of death, heart attack or stroke than the group that switched to tirzepatide. That is a relative difference, not a six-percentage-point drop in any one person’s risk.

How many people were in the study?

The cardiovascular analysis compared 185,705 people who increased semaglutide to 2 mg with 23,104 who switched to tirzepatide: 208,809 people in total. The wider COMPETE SWITCH dataset included 636,525 adults, which is why a larger figure may appear in some coverage.

Was this really Ozempic versus Mounjaro?

Broadly, those are the familiar brand names for the medicines involved. But the actual question was narrower: adults with type 2 diabetes already on semaglutide 1 mg either increased to semaglutide 2 mg or switched to tirzepatide.

Should I switch from Mounjaro to Ozempic because of this study?

No treatment decision should be made on the basis of this study alone. If you are concerned about your heart risk or your current medication, discuss it with your prescribing clinician.

Key Takeaways

• New COMPETE SWITCH CV results were presented at the EASD annual meeting on 29 September 2026.
• US adults with type 2 diabetes who increased semaglutide from 1 mg to 2 mg had a 6% lower relative risk of death, heart attack or stroke than those who switched to tirzepatide (adjusted hazard ratio 1.06 for tirzepatide vs semaglutide).
• The cardiovascular comparison involved 208,809 people: 185,705 who increased semaglutide and 23,104 who switched to tirzepatide.
• It was a retrospective observational analysis of US claims data, not a randomised trial, so it shows an association rather than proof of cause and effect.
• Only around 31% of people who switched to tirzepatide reached 10 mg or more during follow-up, so it was not a comparison of top doses.
• The study involved people with type 2 diabetes on Ozempic doses of semaglutide. It was not a Wegovy or obesity-only study.
• Safety outcomes were not assessed in this analysis.
• It is not a reason to change treatment. Speak to your prescriber if you have concerns.

Further Reading

Mounjaro vs Ozempic UK: Which Weight Loss Injection Works Best?

Weight Loss Jabs & Pills Compared: What the Real Data Shows

Weight Loss Jabs & Pills

Wegovy UK — The Complete Plain English Guide

Sources

Novo Nordisk (29 September 2026) — Ozempic (semaglutide) 2 mg associated with lower risk of major adverse cardiovascular events compared to switching to Mounjaro (tirzepatide) in real-world analysis

Novo Nordisk Science Hub — EASD 2026 congress materials

Reuters (29 September 2026) — Report on Novo Nordisk’s Ozempic vs Mounjaro cardiovascular analysis

This article reports research findings announced by a pharmaceutical company and does not constitute medical advice. Individual circumstances vary. Always speak to an appropriately qualified healthcare professional before making any changes to your treatment.