Semaglutide vs. Tirzepatide: What the Head-to-Head Trial Found

Semaglutide and tirzepatide are two peptide medicines you’re likely to hear discussed together. What makes their research especially useful is that we have a trial that compared them directly. You can see how both groups did under one study design instead of trying to line up percentages from different headlines. 1

What do the two medicines have in common?

Both act on a receptor for GLP-1, a hormone involved in blood sugar regulation and appetite. Tirzepatide also activates the receptor for another hormone called GIP. Researchers can use that difference to form a hypothesis, but what happens in people is best answered by a study that measures outcomes in people. 2

What SURMOUNT-5 found

Researchers randomly assigned 751 adults with obesity and without type 2 diabetes to receive one medicine or the other. After 72 weeks, estimated average weight loss was 20.2% in the tirzepatide group and 13.7% in the semaglutide group. Waist circumference also decreased more on average with tirzepatide. Digestive side effects were the most common in both groups and were generally mild to moderate in the trial. 1

This was an open-label study, meaning participants and study staff knew which treatment they received. That’s useful context for interpreting outcomes, especially self-reported side effects. The results describe averages for the formulations and the group studied; individuals may experience different changes or tolerate treatment differently. 1

Why other results can look different

STEP 1 compared semaglutide with placebo, with support for lifestyle changes in both groups. That trial asks a different question from comparing semaglutide with another medicine. The comparison group and who took part are two of the first things to check before putting results side by side. 3

Researchers in Ireland reviewing these medicines also discuss how other health goals and tolerability can matter to decisions. A larger average change on a single outcome is one piece of that picture. 2

Follow the comparison that fits your question

Before making sense of a headline, ask: Which medicine did the researchers compare it with? Did participants have type 2 diabetes? Which outcomes were reported alongside weight change? Those answers make the numbers much easier to interpret.

Curious how a three-receptor design fits into the discussion? GLP-3R and Retatrutide walks through separate studies and explains why their results aren’t a direct comparison with SURMOUNT-5.

For more international context, Peptide Research From Thailand and Türkiye compares a trial with clinical records from routine care.