Semaglutide vs. Tirzepatide: Which Weight Loss Injection Is Right for You?

Semaglutide and tirzepatide are the two medicines behind most of today’s conversation about weight loss injections. Both are once-weekly injections, both reduce appetite, and both have strong published research behind them. They are not identical, though, and the differences matter when you are deciding which one to start. Montville MedSpa offers both, so this guide sets out the facts side by side.

This article is general information, not medical advice. A consultation with a medical provider determines which medication, if either, is right for you.

What is the difference between semaglutide and tirzepatide?

Short answer: semaglutide acts on one appetite hormone receptor (GLP-1); tirzepatide acts on two (GLP-1 and GIP).

Semaglutide is a GLP-1 receptor agonist. It mimics GLP-1, a hormone released by the gut after eating that signals fullness, slows stomach emptying and helps regulate blood sugar. It is the active ingredient in Ozempic® (type 2 diabetes) and Wegovy® (chronic weight management).

Tirzepatide is a dual GIP and GLP-1 receptor agonist. GIP (glucose-dependent insulinotropic polypeptide) is a second gut hormone involved in insulin release and energy balance. By acting on both receptors, tirzepatide combines the effects of the two hormones. It is the active ingredient in Mounjaro® (type 2 diabetes) and Zepbound® (chronic weight management).

As our weight loss injections page puts it, semaglutide helps regulate appetite and blood sugar, while tirzepatide combines the benefits of GLP-1 and GIP receptor agonists to enhance glucose control and promote weight reduction.

Which one causes more weight loss?

Short answer: in published trials, tirzepatide produced more weight loss on average, but both produced substantial results and individual responses vary.

The headline numbers from the major trials, all of which combined medication with diet and exercise:

Trial	Medication	Average weight loss
STEP 1	Semaglutide 2.4 mg weekly	About 15% of body weight over 68 weeks
SURMOUNT-1	Tirzepatide, highest dose (15 mg) weekly	About 21% of body weight over 72 weeks
SURMOUNT-5 (head to head)	Tirzepatide vs. semaglutide	About 20% vs. about 14% over 72 weeks

SURMOUNT-5, published in 2025, compared the two medicines directly in adults with obesity and without diabetes. On average, people taking tirzepatide lost more weight than people taking semaglutide.

Averages hide a lot of variation. Some people respond very well to semaglutide; others do better on tirzepatide; some find one easier to tolerate than the other. These are trial results, not a prediction for any individual, and they are not results from Montville MedSpa’s own patients.

How do the side effects compare?

Short answer: very similar. Both most commonly cause nausea, diarrhea, constipation and vomiting, mostly while the dose is being increased.

Because both medicines act on GLP-1, their side effect profiles overlap heavily. The digestive symptoms tend to be mild to moderate and usually ease as the body adjusts. In the SURMOUNT-5 trial, the rates of gastrointestinal side effects were broadly similar for the two drugs.

Both also carry the same FDA boxed warning about thyroid C-cell tumors seen in rodent studies, so neither is used by people with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN2). Neither is used during pregnancy.

One practical difference: the prescribing information for tirzepatide notes that it can make birth control pills less effective, particularly after starting and after each dose increase, and recommends using a non-oral or backup method of contraception during those periods. Tell your provider if you use oral contraceptives.

For a full guide to managing symptoms, see semaglutide side effects and how to manage them. Most of that advice applies to tirzepatide as well.

How are they taken?

Short answer: both are once-weekly injections under the skin, started at a low dose and increased gradually.

Both are given on the same day each week, typically into the stomach, thigh or upper arm. Both follow a step-up approach: a low starting dose that is increased at intervals, so the body has time to adjust and side effects stay manageable. Your provider decides your own dose and how quickly to increase it, and adjusts the plan at your check-ins.

Which one should I choose?

Short answer: the one that suits your health history, your goals and how your body responds, chosen together with your provider.

There is no single right answer, which is why the choice is made at a consultation rather than from a chart. Things your provider will weigh include:

• Your goals. How much weight you are hoping to lose and over what timeframe.
• Your medical history. Conditions such as type 2 diabetes, a history of pancreatitis or gallbladder disease, and kidney function all matter.
• Other medications. Including insulin or other blood sugar medicines, and oral contraceptives.
• Past experience. If you have tried one before, how well you tolerated it and how you responded.
• Tolerability as you go. If side effects are hard to manage on one, adjusting the dose or switching is something to discuss with your provider.

What does starting either one look like at Montville MedSpa?

Short answer: a consultation, a personalized plan, and regular monitoring.

1. Initial consultation. Our medical professionals assess your health, weight loss goals and medical history to determine the most suitable weight loss injection for you.
2. Personalized plan. Your plan covers the type and dosage of injection, dietary recommendations and exercise guidance.
3. Regular monitoring. Regular check-ins and adjustments keep the plan working and address any concerns.

If you are new to these medicines, our guide to what to expect in your first 3 months on semaglutide describes the early weeks, and much of it applies to tirzepatide too.

Frequently asked questions

Is tirzepatide stronger than semaglutide?

In the head-to-head SURMOUNT-5 trial, tirzepatide produced greater average weight loss than semaglutide. “Stronger” on average does not mean better for everyone; tolerability and your medical history matter just as much.

Can I switch from semaglutide to tirzepatide?

Switching between the two is sometimes considered, for example if one is not working well or is hard to tolerate. It should only be done under the guidance of your provider, who will decide the starting dose and timing.

Are Ozempic and Mounjaro the same as Wegovy and Zepbound?

They share active ingredients: Ozempic® and Wegovy® both contain semaglutide, and Mounjaro® and Zepbound® both contain tirzepatide. The diabetes and weight management versions have different approved uses and doses.

Do I need to change my diet on either medication?

Yes. The trials combined each medication with a reduced-calorie diet and more physical activity, and your plan at Montville MedSpa includes dietary and exercise guidance for that reason. Both medicines sit within our wider wellness services.

Find out which weight loss injection fits you

The best way to choose between semaglutide and tirzepatide is a conversation with a medical provider who knows your history. Contact Montville MedSpa to book a consultation in Montville, NJ, and learn more on our weight loss injections page.