Semaglutide vs Tirzepatide: Efficacy, Side Effects, and Cost

You have probably seen both medications mentioned online, sometimes interchangeably, sometimes as though one is clearly superior. The research gives a more specific picture. Both medications produced meaningful weight loss in trials. In the one trial that compared them directly, tirzepatide produced more on average. But the right medication for you depends on your health history, cost, and what a licensed provider decides is clinically appropriate for your situation.

The mechanism difference: one receptor vs. two

This is the basic distinction between the medications.

Semaglutide is a GLP-1 receptor agonist. It activates one receptor type, the GLP-1 receptor. GLP-1 helps regulate appetite and how much you eat, and GLP-1 receptors are found in areas of the brain involved in appetite^[5].

Tirzepatide is a GIP receptor and GLP-1 receptor agonist. It activates the GLP-1 receptor (the same target as semaglutide) and the GIP receptor (glucose-dependent insulinotropic polypeptide). According to the Zepbound label, nonclinical studies suggest the added GIP action may further contribute to the regulation of food intake^[6].

That second pathway is one proposed reason tirzepatide produced more average weight loss in trials. It has not been proven to be the reason, and it does not mean semaglutide does not work. Semaglutide produced substantial weight loss in its own trials. The useful question is not “does it work” but “which works better on average, and which fits you.”

Weight loss efficacy: what the trials show

Four trials matter most here. Each one studied the manufacturers’ brand-name medicines, not compounded versions.

STEP 1: Semaglutide 2.4mg

The STEP 1 trial (New England Journal of Medicine, 2021) enrolled 1,961 adults with a BMI of 30 or higher, or 27 or higher with at least one weight-related condition, who did not have diabetes. Participants took once-weekly semaglutide 2.4mg or placebo for 68 weeks, alongside a lifestyle program. Average weight loss was 14.9% on semaglutide versus 2.4% on placebo, or about 15.3 kg (roughly 34 pounds) versus 2.6 kg^[2]. About half (50.5%) of participants on semaglutide lost 15% or more. Results varied widely from person to person.

SURMOUNT-1: Tirzepatide at multiple doses

The SURMOUNT-1 trial (New England Journal of Medicine, 2022) enrolled 2,539 adults with a BMI of 30 or higher, or 27 or higher with at least one weight-related complication, excluding diabetes. Participants took once-weekly tirzepatide 5mg, 10mg, or 15mg or placebo for 72 weeks. Average weight loss was 15.0% at 5mg, 19.5% at 10mg, and 20.9% at 15mg, compared with 3.1% on placebo^[3].

STEP 1 and SURMOUNT-1 were separate trials with different participants, durations (68 vs. 72 weeks), and designs, so their results cannot be compared directly. Setting 14.9% next to 20.9% is a cross-trial comparison, and it can mislead. That is why SURMOUNT-5 matters.

SURMOUNT-5: Head-to-head comparison

This is the most directly relevant trial for your decision. SURMOUNT-5 (New England Journal of Medicine, 2025) randomly assigned 751 adults with obesity but without type 2 diabetes to the highest dose they tolerated of tirzepatide (10mg or 15mg) or semaglutide (1.7mg or 2.4mg), injected once weekly for 72 weeks^[1].

Results at 72 weeks^[1]:

• Tirzepatide: average weight loss of 20.2%
• Semaglutide: average weight loss of 13.7%
• Waist circumference: down an average of 18.4 cm with tirzepatide and 13.0 cm with semaglutide
• Participants on tirzepatide were more likely to reach weight loss of at least 10%, 15%, 20%, and 25%

A few things to keep in mind. The trial was open-label (participants knew which medication they were taking) and was funded by Eli Lilly, which makes tirzepatide^[1]. It did not include people with type 2 diabetes. The semaglutide doses studied topped out at 2.4mg; the current Wegovy label now allows a higher maximum of 7.2mg once weekly for some adults, which SURMOUNT-5 did not test^[5]. And these are averages, not a prediction for any individual. Results vary.

What this means for your choice

In SURMOUNT-5, tirzepatide produced greater average weight loss than semaglutide. But “average” hides individual variation. Some people on semaglutide lose more weight than some people on tirzepatide. Biology, dose, how consistently you take it, eating habits, activity, and sleep all influence outcomes.

Here is a practical way to read it. If you are just starting, the head-to-head data favors tirzepatide on average weight loss, and a licensed provider can weigh that against your health history, coverage, and cost. If you are already on semaglutide, responding well, and tolerating it, the trial does not mean you need to switch. Cost and insurance coverage often decide it in practice; see the cost section below.

Whichever medication you take, plan for it to be long term. In SURMOUNT-4, adults who had lost an average of 20.9% on tirzepatide and were then switched to placebo regained an average of 14.0% of body weight over the next 52 weeks, while those who continued lost a further 5.5%^[4]. Stopping often leads to regain, so plan any change with your prescriber.

A licensed provider will also consider your other conditions. The two medications have different FDA-approved uses beyond weight management (see the label table below), and that can matter more for some people than average weight loss.

Side effects: are they different?

Both medications have similar gastrointestinal side effect profiles. In SURMOUNT-5, the most common side effects in both groups were gastrointestinal, most were mild to moderate, and they happened mainly while the dose was being increased^[1].

On the current labels, the most common side effects of Wegovy include nausea, diarrhea, vomiting, constipation, abdominal pain, headache, fatigue, indigestion, dizziness, bloating, burping, low blood sugar in people with type 2 diabetes, gas, stomach flu, reflux, and hair loss^[5]. The most common side effects of Zepbound include nausea, diarrhea, vomiting, constipation, abdominal pain, indigestion, injection site reactions, fatigue, allergic reactions, burping, hair loss, and reflux^[6].

Both labels carry a boxed warning about thyroid C-cell tumors seen in rodents. It is unknown whether either medication causes these tumors, including medullary thyroid carcinoma, in humans. Neither should be used by people with a personal or family history of medullary thyroid carcinoma or with Multiple Endocrine Neoplasia syndrome type 2, or by people with a known serious allergy to the medication^[5][6].

Both labels also warn about acute pancreatitis, gallbladder disease, low blood sugar when used with insulin or sulfonylureas, kidney injury from dehydration, severe gastrointestinal reactions, serious allergic reactions, diabetic retinopathy complications in people with type 2 diabetes, and the risk of inhaling stomach contents during anesthesia or deep sedation. The Wegovy label also lists heart rate increase^[5][6]. Both medications slow stomach emptying, which can affect how other oral medicines are absorbed. The Zepbound label advises people taking birth control pills to switch to a non-oral method, or add a barrier method, for 4 weeks after starting and for 4 weeks after each dose increase^[6]. Both should be stopped if pregnancy is recognized when used for weight reduction^[5][6].

If you have had side effects on one medication, that does not guarantee you will have the same on the other. Tolerance is individual. Some people who feel nauseated on semaglutide tolerate tirzepatide well, and vice versa.

For both medications, the labels use a gradual dose escalation schedule to reduce gastrointestinal side effects^[5][6]. Rushing it tends to make nausea and stomach upset worse. Your prescriber sets the schedule. For a closer look at side effect rates, see semaglutide vs tirzepatide side effects, and for body composition, muscle loss on semaglutide vs tirzepatide.

Current FDA label differences

The brand-name medications approved for weight management are Wegovy (semaglutide, Novo Nordisk) and Zepbound (tirzepatide, Eli Lilly). The same molecules are also sold under other names for type 2 diabetes: Ozempic injection and Rybelsus/Ozempic tablets (semaglutide)^[8][9] and Mounjaro (tirzepatide)^[7]. This table summarizes the weight-management labels as of October 16, 2026.

Sources: Wegovy prescribing information, Revised 06/2026^[5]; Zepbound prescribing information, Revised 08/2026^[6]. Both labels pair the medication with a reduced-calorie diet and increased physical activity. There is no FDA-approved oral tirzepatide.

Cost comparison

Prices vary by program and dose, and the gap between the two medications depends on how you buy them. A few things drive the total:

• Brand-name or compounded. Brand-name prices depend on your insurance coverage, any manufacturer self-pay program, and the pharmacy. Compounded prices vary by program.
• Dose and form. Some sellers charge more for higher doses. Pens, vials, and tablets can be priced differently.
• What is bundled. Some programs include provider visits, labs, and shipping in one price; others bill them separately.
• Coverage. Insurance plans differ in whether they cover either medication for weight management, and which one they prefer.

Compare the total cost: medication, dose increases, provider visits, labs, shipping, membership fees, and cancellation terms. A low starting price can rise as the dose goes up. Our medication pricing guide and the formulations and dose reference walk through what to check.

If you are looking at compounded versions, know what they are. Compounded semaglutide and tirzepatide are not FDA-approved, the FDA does not review them for safety, effectiveness, or quality, and they are not the same as Wegovy or Zepbound^[11]. None of the trials on this page studied compounded products. FDA has determined that the tirzepatide injection shortage (decision reissued December 19, 2024) and the semaglutide injection shortage (February 21, 2025) are resolved, and the periods during which FDA did not intend to act against compounders over shortage-dependent conditions have ended (FDA page current as of 04/01/2026)^[10]. See compounded medications for more.

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Who might prefer semaglutide?

Cost and coverage: Depending on your insurance and the program, semaglutide may cost you less. Compare the total cost of both before deciding.

Prior success: If you have used semaglutide before, responded well, and tolerated it without significant side effects, the head-to-head results alone are not a reason to switch.

A pill option: Wegovy is available as a once-daily tablet as well as a weekly injection^[5]. If you would rather not inject, that is currently the only FDA-approved oral option of the two.

Heart or liver conditions: Wegovy is FDA-approved to lower the risk of major cardiovascular events in adults with established cardiovascular disease and obesity or overweight, and (as an injection) to treat MASH with moderate to advanced liver fibrosis^[5]. A provider may weigh those indications if they apply to you.

Longer track record: Semaglutide was first approved by the FDA in 2017; tirzepatide in 2022^[5][6]. If you prefer a medication with longer use in practice, semaglutide fits that description.

Who might prefer tirzepatide?

Greater average weight loss: In SURMOUNT-5, average weight loss was greater with tirzepatide (20.2% vs. 13.7% at 72 weeks)^[1]. That is an average across participants, not a guarantee for you.

Sleep apnea: Zepbound is FDA-approved to treat moderate to severe obstructive sleep apnea in adults with obesity^[6].

Individual response: You only learn how you respond to a medication by taking it. If someone on semaglutide reaches a plateau, a provider may discuss switching to tirzepatide. If tirzepatide causes side effects that cannot be managed, semaglutide is another option. Our guide to switching between semaglutide and tirzepatide covers how that usually works.

If you have type 2 diabetes, note that SURMOUNT-5 did not include people with diabetes^[1], and both molecules are also sold under separate brand names for diabetes (Ozempic and Rybelsus for semaglutide, Mounjaro for tirzepatide)^[7][8][9].

How to decide

The decision should involve you and a licensed provider. At most telehealth programs and clinics, the provider will consider:

1. Your health history (prior reactions to medications, existing conditions, current medications)
2. Your weight goals and what is clinically realistic for you
3. Your cost situation and what you can sustain long term
4. Any preference you have based on research or prior experience, including whether you want a pill or an injection

In the head-to-head trial, tirzepatide produced more weight loss on average. Both medications produced substantial weight loss compared with placebo in their own trials. The right medication for you is the one you can take consistently, that a provider decides is appropriate for your health, and that fits your budget.

Neither medication replaces eating habits and movement. Both labels pair the medication with a reduced-calorie diet and increased physical activity^[5][6]. Some programs include nutrition guidance, fitness support, or coaching; others do not, so check what is included before you sign up.

Next steps

If you are trying to choose between the two, bring these questions to any program you are considering: which medication and form they offer, whether they prescribe brand-name or compounded products, what the price is at each dose, and what is included. At most telehealth programs, a licensed provider reviews your health history and decides whether a prescription is appropriate, and which one. That decision may be semaglutide, tirzepatide, or neither.

If you have already started on one medication and want to understand switching, see the guide on transitioning between semaglutide and tirzepatide. If you want a detailed dosing breakdown, the tirzepatide vs semaglutide dosage chart walks through escalation schedules and unit conversions.

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Citations

[1] Aronne LJ, Horn DB, le Roux CW, et al. “Tirzepatide as Compared with Semaglutide for the Treatment of Obesity.” N Engl J Med. 2025;393(1):26-36. https://pubmed.ncbi.nlm.nih.gov/40353578/ (SURMOUNT-5: design, 20.2% vs 13.7% weight loss, waist circumference, side effects, funding.)

[2] Wilding JPH, Batterham RL, Calanna S, et al. “Once-Weekly Semaglutide in Adults with Overweight or Obesity.” N Engl J Med. 2021;384(11):989-1002. https://pubmed.ncbi.nlm.nih.gov/33567185/ (STEP 1: 14.9% vs 2.4% at 68 weeks.)

[3] Jastreboff AM, Aronne LJ, Ahmad NN, et al. “Tirzepatide Once Weekly for the Treatment of Obesity.” N Engl J Med. 2022;387(3):205-216. https://pubmed.ncbi.nlm.nih.gov/35658024/ (SURMOUNT-1: 15.0%, 19.5%, 20.9% vs 3.1% at 72 weeks.)

[4] Aronne LJ, Sattar N, Horn DB, et al. “Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial.” JAMA. 2024;331(1):38-48. https://pubmed.ncbi.nlm.nih.gov/38078870/ (Regain after stopping tirzepatide.)

[5] U.S. Food and Drug Administration. WEGOVY (semaglutide) injection and tablets, prescribing information. Revised 06/2026. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/215256s025lbl.pdf

[6] U.S. Food and Drug Administration. ZEPBOUND (tirzepatide) injection, prescribing information. Revised 08/2026. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/217806Orig1s041correctedlbl.pdf

[7] U.S. Food and Drug Administration. MOUNJARO (tirzepatide) injection, prescribing information. Revised 04/2026. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/215866Orig1s052lbl.pdf

[8] U.S. Food and Drug Administration. OZEMPIC (semaglutide) injection, prescribing information. Revised 05/2026. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/209637Orig1s039lbl.pdf

[9] U.S. Food and Drug Administration. RYBELSUS and OZEMPIC (semaglutide) tablets, prescribing information. Revised 1/2026. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/213051Orig1s030lbl.pdf

[10] U.S. Food and Drug Administration. “FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize.” Content current as of 04/01/2026. https://www.fda.gov/drugs/drug-alerts-and-statements/fda-clarifies-policies-compounders-national-glp-1-supply-begins-stabilize (Accessed 2026-10-16.)

[11] U.S. Food and Drug Administration. “FDA’s Concerns with Unapproved GLP-1 Drugs Used for Weight Loss.” Content current as of 10/01/2026. https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss (Accessed 2026-10-16.)