Tirzepatide vs. semaglutide: what the head-to-head trial shows

If you are thinking about a weight loss medication, you have probably run into two names: tirzepatide and semaglutide. For years, people compared them using separate trials, which is a bit like comparing two runners on different days. Now there is a trial that put them on the same track. Here is what it found, what it left out, and how we think about the choice with you.

The two medications, briefly

Semaglutide, sold as Wegovy for weight management, is a GLP-1 medication. It mimics a gut hormone that helps control appetite and blood sugar.

Tirzepatide, sold as Zepbound for weight management, is a GIP/GLP-1 medication. It mimics the same gut hormone and a second one, called GIP. Both are given as a weekly injection, and both are meant to be used alongside changes in eating and activity.

What the head-to-head trial found

The study is called SURMOUNT-5. It enrolled 751 adults with obesity who did not have type 2 diabetes and randomly assigned them to tirzepatide or semaglutide at the highest dose each person could tolerate. The trial ran for 72 weeks. The New England Journal of Medicine published the results.

Average weight loss at 72 weeks was 20.2% with tirzepatide and 13.7% with semaglutide. Waist circumference fell by about 18.4 cm with tirzepatide and 13.0 cm with semaglutide. People taking tirzepatide were also more likely to reach weight loss of at least 10%, 15%, 20%, and 25%.

So on average, tirzepatide outperformed semaglutide in this trial. We say "on average" on purpose. Some people lose a lot on semaglutide, and some lose less than expected on tirzepatide.

What the trial does not tell you

A few limits are worth knowing:

• It was open-label. Participants and clinicians knew which drug was being used. That is common in medication trials, but it can affect how people report their experience.
• The manufacturer of tirzepatide funded it. The design looks sound, but it is fair to note where the money came from.
• It excluded people with type 2 diabetes. The results do not directly apply if you have diabetes.
• It tested maximum tolerated doses. Many people take lower doses in real life, and results at lower doses may differ.

Side effects and how people feel

In the trial, the most common side effects for both medications were gastrointestinal, and most were mild to moderate. They happened mostly while the dose was being increased. Nausea, diarrhea, and constipation are the usual complaints with both.

A later analysis looked at people who lost weight quickly. In that post hoc analysis, fast responders had more gastrointestinal and liver-related side effects, but they finished treatment at similar rates to everyone else. Another analysis found that health-related quality of life improved with both medications, with a somewhat larger improvement in general health scores with tirzepatide.

Neither drug is a fit for everyone. People with certain personal or family histories, a history of pancreatitis, or who are pregnant or planning pregnancy need individual guidance. We review your history before prescribing either one.

Setting realistic expectations

Averages can hide a lot. The same trial reported that about 44% of people on tirzepatide and 21% on semaglutide had lost at least 15% of their body weight by week 24, which means many people on either drug took longer to reach their results. Weight loss usually slows and levels off over time, and the medication works best when it is paired with protein-rich meals, regular movement, and strength training to protect muscle.

It also helps to plan for the long term early. These medications treat a chronic condition, and weight tends to return for many people who stop them. That is why we talk about maintenance from the first visit, not only about the first 20 pounds.

Cost and coverage

This is where the answer often changes. Tirzepatide tends to produce more weight loss, but it is newer and often more expensive, and your plan may cover one drug and not the other.

Industry-supported modeling studies disagree about value. One US simulation based on SURMOUNT-5 estimated lower long-term costs with tirzepatide, mostly by projecting fewer cases of diabetes and heart disease. A shorter analysis from Greece found semaglutide cheaper at lower weight loss targets and tirzepatide favored at higher targets, with no statistically significant difference overall. Models depend on their assumptions, so treat them as context rather than a verdict.

In practice, the best medication is often the one you can get covered, afford for as long as you need it, and tolerate.

How we help you choose

We start with your goals, your health history, and your plan. A few questions guide the choice:

• How much weight do you need to lose to improve your health, such as blood pressure, blood sugar, or sleep apnea?
• Do you have type 2 diabetes or prediabetes, which changes the options?
• Which medication does your plan cover, and what will it cost you month to month?
• How have you tolerated medications that affect digestion in the past?
• What is your plan for the long term, including what happens if you stop?

Starting a medication is only part of the work. We follow your progress, adjust doses, and watch for side effects, so the choice is not a one-time decision.

Next steps

If you want to talk through tirzepatide, semaglutide, or another option, we can help. Stonewood Health offers telehealth endocrinology and weight management by appointment, and most major plans are accepted, including Medicare. Primary care should not be something you buy on top of the coverage you already pay for. Learn more and book at our endocrinology page.