Tirzepatide vs semaglutide: trial results, side effects, cost

Tirzepatide and semaglutide are the two injectable medications most people are choosing between when they start weight loss treatment. They are related but not identical, and the differences that matter are the receptor pathways, the labeled uses, one head to head trial, tolerability, and price. This guide walks through each, with sources, and points you to a licensed provider for the decision about your own care. For more background reading, the Belle Learn hub collects the rest of our clinician reviewed guides.

Two hormones vs one

Semaglutide is described in the Wegovy prescribing information as a glucagon-like peptide-1 (GLP-1) receptor agonist. Tirzepatide is a dual receptor agonist: it acts at the glucose-dependent insulinotropic polypeptide (GIP) receptor in addition to the GLP-1 receptor. That is the structural difference behind the phrase you see everywhere, two hormone pathways versus one.

The labeled uses also differ, and this is where the brand prescribing information is worth reading closely. Per DailyMed, Zepbound (tirzepatide) is indicated, in combination with a reduced-calorie diet and increased physical activity, to reduce excess body weight and maintain weight reduction long term in adults with obesity or adults with overweight in the presence of at least one weight-related comorbid condition, and to treat moderate to severe obstructive sleep apnea (OSA) in adults with obesity. Wegovy (semaglutide) is indicated, in combination with a reduced calorie diet and increased physical activity, to reduce the risk of major adverse cardiovascular events (cardiovascular death, non-fatal myocardial infarction, or non-fatal stroke) in adults with established cardiovascular disease and either obesity or overweight, and to reduce excess body weight and maintain weight reduction long term in adults and pediatric patients aged 12 years and older with obesity.

Both molecules are also available in compounded form through telehealth clinics, including compounded tirzepatide and compounded semaglutide at Belle. Compounded medications are not FDA approved finished products. A licensed provider determines eligibility. The FDA describes compounding as a practice in which a licensed pharmacist or a licensed physician combines, mixes or alters ingredients of a drug to create a medication tailored to the needs of an individual patient, and states that compounded drugs are not FDA approved, meaning the agency does not review their safety, effectiveness or quality before they are marketed. In plain terms, compounded medications are custom-prepared by licensed compounding pharmacies and are not evaluated by the FDA for safety or effectiveness.

What the head to head trial found

Until 2025, most comparisons between tirzepatide and semaglutide were indirect, meaning people lined up separate trials run in different populations. SURMOUNT-5, published in the New England Journal of Medicine in 2025, compared them directly.

What the trial looked at: tirzepatide as compared with semaglutide for the treatment of obesity. What it reported: a total of 751 participants underwent randomization, and the least-squares mean percent change in weight at week 72 was 20.2% (95% confidence interval, 21.4 to 19.1) with tirzepatide and 13.7% (95% confidence interval, 14.9 to 12.6) with semaglutide, with P<0.001.

Read that as a trial result, not a forecast for you. Three points of context help. First, those are least-squares mean values across a randomized group, so individual results inside the trial sat both above and below the averages. Second, the measurement point was week 72, which is a long runway compared with how most people judge a new medication after a month or two. Third, both arms were studied alongside lifestyle change, which is also how both brand labels describe their use.

A single well run trial is useful evidence and it is still one trial in one population. Your own history, other conditions, medication list and tolerance matter more to your outcome than a percentage in a table, which is why the starting decision belongs with a licensed provider who can see your full picture. You can read about the Belle clinical team if you want to know who reviews these visits.

Side effects

Here is the honest framing. The SURMOUNT-5 report we cite above is a weight outcome result, so we are not going to attach invented side effect rates to it. The authoritative list for each medication is the prescribing information, which sets out warnings, contraindications and adverse reactions in full. The Zepbound prescribing information and the Wegovy prescribing information are both published on DailyMed and free to read before your visit.

What to do with that information, practically:

• Read the warnings and contraindications sections for tirzepatide and semaglutide before your consultation, and note anything that applies to you.
• Bring your full medication list, including supplements, and your personal and family medical history to the visit.
• Tell your provider about prior experience with any GLP-1 class medication, including anything you stopped and why.
• Report new or worsening symptoms to your provider rather than adjusting on your own. Dose decisions are clinical decisions.
• Plan the food side of treatment early. Belle nutrition guidance exists because eating patterns change once treatment starts.

For compounded versions of either molecule, add one more step. Because compounded drugs are not FDA approved, the agency does not review their safety, effectiveness or quality before they are marketed, so you want a program where a licensed provider evaluates you first, a licensed compounding pharmacy prepares the medication, and someone clinical is reachable after the medication arrives.

Cost

Cost is usually the deciding factor once a provider has said both tirzepatide and semaglutide are reasonable options. Belle publishes live pricing rather than a number inside an article, because pricing moves and a stale figure is worse than none.

When you compare programs, compare the whole cost of a month, not the headline. Things worth asking about:

1. Does the advertised price hold after the first month, or is it an introductory rate that resets? Some programs reset intro pricing after month one.
2. Is the medical visit included, and is follow up with a provider included when something needs adjusting?
3. Are shipping and injection supplies included, or billed separately?
4. Is there a cancellation window, and what happens to an unused month?
5. Does the price change as your plan changes over time?

Two Belle guides go deeper on the numbers: compounded tirzepatide cost and compounded semaglutide cost. If you are also weighing compounded medication against a brand prescription, compounded semaglutide vs Wegovy and Ozempic covers what is actually different between those paths.

Who tends to start on which

There is no universal answer, and anyone who gives you one without reviewing your history is guessing. What a provider weighs generally comes down to a handful of practical factors.

Labeled use that matches your situation

The two labels are not interchangeable. The Zepbound label for tirzepatide includes treatment of moderate to severe obstructive sleep apnea in adults with obesity. The Wegovy label for semaglutide includes reducing the risk of major adverse cardiovascular events in adults with established cardiovascular disease and either obesity or overweight, and it covers pediatric patients aged 12 years and older with obesity as well as adults. If one of those descriptions fits you, it is a real input into the conversation.

Prior experience and tolerance

People who have already tried one of these medications usually come in with information: what happened, how they felt, whether they were able to stay on it. That history is often more decisive than any comparison chart.

Trial evidence, kept in proportion

SURMOUNT-5 reported a larger mean percent weight change at week 72 with tirzepatide than with semaglutide in the randomized population described above. That is a legitimate reason some people ask about tirzepatide first. It is not a guarantee about any single person, and it does not override the label, your history or cost.

Access and budget over 12 months

Weight treatment is measured in months, not weeks, which means the price you can sustain for a year matters more than the price of your first box. Choose the option you can actually stay on while you build the eating and activity habits both labels describe as part of treatment.

If you want to see the full set of options before booking, the weight loss treatments page lists what Belle offers, and all treatments covers the rest of the clinic, including longevity and skin. Whichever direction you lean, bring the questions above to a licensed provider and let the plan follow your history rather than a headline.