Semaglutide vs Tirzepatide: What Research Says and What to Track

If you are on semaglutide or tirzepatide, you have probably seen the headlines comparing them. One gets called stronger, the other gets called gentler, and the internet fills in the rest. This post walks through what the published research actually reports, in plain language, and then covers the part you control: keeping a clean record with a GLP-1 tracker so your provider has real data to work with.

Nothing here is a reason to switch, start or stop anything. Which medication fits you, and at what dose, is a decision for your licensed healthcare provider.

What semaglutide and tirzepatide are

Both belong to a group of medicines built around GLP-1, a gut hormone involved in appetite and blood sugar. The difference is in how many hormone pathways each one targets.

• Semaglutide acts on the GLP-1 receptor.
• Tirzepatide acts on two receptors: GLP-1 and GIP, another gut hormone. Researchers describe it as a dual agonist.

That one-versus-two difference is the main reason the two get compared so often. Whether it matters for any one person is not something a blog post can answer.

What the research reports

Three large trials published in the New England Journal of Medicine come up in almost every comparison. Here is what each one found, stated as the researchers reported it.

Semaglutide in STEP 1

The STEP 1 trial followed 1,961 adults with overweight or obesity who did not have diabetes. Everyone also followed a lifestyle program. Over 68 weeks, the semaglutide group lost an average of 14.9% of body weight, compared with 2.4% in the placebo group. The authors noted that more people on semaglutide than placebo stopped treatment because of gastrointestinal side effects.

Tirzepatide in SURMOUNT-1

The SURMOUNT-1 trial enrolled 2,539 adults with obesity or overweight, again without diabetes. Over 72 weeks, average weight change in the tirzepatide groups ranged from about 15% to about 21% depending on the dose group, compared with about 3% on placebo.

The head to head trial, SURMOUNT-5

Comparing two separate trials has limits, because the people, timelines and methods differ. That is why the SURMOUNT-5 trial got so much attention. It put 751 adults with obesity, without type 2 diabetes, on one medication or the other and compared them directly for 72 weeks.

The reported results:

• Average weight change was about 20.2% with tirzepatide and about 13.7% with semaglutide.
• Tirzepatide also showed a larger reduction in waist size.
• In both groups, the most common side effects were gastrointestinal. Most were mild to moderate and showed up mainly while doses were being stepped up.

A few honest caveats belong next to those numbers. The trial was open label, meaning participants knew which medication they were on. It was funded by Eli Lilly, the company that makes tirzepatide. And these are averages across hundreds of people. Individual results in all three trials varied widely, and your own experience may look nothing like the average.

Why averages do not answer your question

Research tells you what happened to a group. Your provider is trying to understand what is happening to you. Those are different questions.

Two people on the same medication can have very different weight trends, side effects and schedules. Your provider weighs your health history, other medications, how you are tolerating things and many factors that never show up in a headline. That is exactly why your own records matter so much. They are the closest thing to a personal study your provider can look at.

What to track on either medication

The good news is that tracking looks almost the same whichever one you use. A solid GLP-1 tracker routine covers five things.

1. Every dose, as given

Log the date, the time and the dose your provider gave you, in the unit your provider used. If you miss one or take it late, log that too. A gap you recorded is more useful than a gap nobody can explain. Peppy keeps this in a dose history with an on-time percentage you can show at appointments.

2. Your titration steps

Both medications are often adjusted in steps over time. Write down each step your provider gives you and the date it started. When you later notice a change in side effects, you can see whether it lined up with a step. You can set this up as a ladder in the titration schedule feature, following the guide on titration ladders and cycles.

3. Weight, on a steady routine

Weigh at a similar time of day under similar conditions. Day to day numbers bounce around, so the trend over weeks says more than any single reading. A weight tracking chart next to your doses makes that trend easy to read with your provider.

4. Side effects, with a rating

Since gastrointestinal effects were the most common in the trials above, it is worth noting what you feel, how strong it was and when it happened. A simple mild, moderate or severe rating keeps it consistent. Do not try to decide what a symptom means on your own. Bring the log and let your provider interpret it.

5. Injection sites

Note where each injection went. A rotation record helps you avoid using the same spot too often. Peppy shows this on a body map in injection site rotation.

If your provider switches you

Some people move from one medication to the other. If that happens, a few record keeping habits make the transition cleaner:

• Mark the switch date clearly so your weight and side effect history splits into a before and after.
• Start a fresh entry for the new medication rather than editing the old one. That way your old history stays intact.
• Record the new vial or pen details exactly as your provider or pharmacist describes them. Peppy's vial tracker helps you see what is left and when you will run low.
• Write down questions as they come up. A short list on your phone is easier to bring to the next visit than trying to remember everything.

You can read more about tracking each medication on the dedicated semaglutide tracker and tirzepatide tracker pages, or the broader GLP-1 tracker overview.

Bringing it to your appointment

Before a visit, take two minutes to review the last few weeks. Look for missed or late doses, any titration step that started, your weight trend and any side effects rated moderate or higher. That short summary turns a vague "it has been fine, I think" into a clear picture.

Research comparing semaglutide and tirzepatide is useful background. But the most useful data in the room will be your own. A steady GLP-1 tracker habit, kept honestly, gives you and your provider something concrete to decide from.