Quick answer: In the first major head-to-head obesity trial, tirzepatide produced greater average weight loss than semaglutide after 72 weeks. Participants taking tirzepatide lost an average of 20.2% of their starting weight, compared with 13.7% among those taking semaglutide.[1]

However, this does not mean tirzepatide is automatically the best medication for everyone. Your medical history, treatment goals, insurance coverage, side effects, cardiovascular health, diabetes status and ability to stay on treatment all matter.

This article compares the injectable weight-management medications:

• Zepbound, which contains tirzepatide
• Wegovy, which contains semaglutide

Mounjaro also contains tirzepatide, while Ozempic contains semaglutide, but those brands are primarily approved for treating type 2 diabetes. Although people often use the brand names interchangeably, they do not have identical FDA-approved indications.

Tirzepatide vs semaglutide at a glance

Feature	Tirzepatide	Semaglutide
Weight-management brand	Zepbound	Wegovy
Type 2 diabetes brand	Mounjaro	Ozempic
Medication class	GIP and GLP-1 receptor agonist	GLP-1 receptor agonist
Typical frequency	Once weekly	Once weekly for the injectable formulation
Average weight loss in SURMOUNT-5	20.2% after 72 weeks	13.7% after 72 weeks
Maximum dose studied in SURMOUNT-5	15 mg weekly	2.4 mg weekly
Notable additional indication	Moderate-to-severe obstructive sleep apnea in adults with obesity	Cardiovascular risk reduction in certain adults with established cardiovascular disease and overweight or obesity
Common side effects	Nausea, diarrhea, vomiting, constipation and abdominal symptoms	Nausea, diarrhea, vomiting, constipation and abdominal symptoms

The percentages above are clinical-trial averages, not promises. Some participants lost considerably more, while others lost less or discontinued treatment.

Which medication produced more weight loss?

The best direct comparison comes from the 2025 SURMOUNT-5 trial, which included 751 adults with obesity who did not have type 2 diabetes.[1]

Participants were randomly assigned to receive the maximum tolerated dose of either:

• Tirzepatide at 10 or 15 mg once weekly
• Semaglutide at 1.7 or 2.4 mg once weekly

Both medications were gradually increased to reduce side effects. After 72 weeks, the average changes were:

Result after 72 weeks	Tirzepatide	Semaglutide
Average body-weight change	-20.2%	-13.7%
Average waist-circumference change	-18.4 cm	-13.0 cm

Participants assigned to tirzepatide were also more likely to reach weight-loss thresholds of at least 10%, 15%, 20% and 25%.[1]

For a person starting at 250 pounds, the trial averages would equal approximately:

• 50.5 pounds with tirzepatide
• 34.3 pounds with semaglutide

That calculation only illustrates the percentages. It does not predict what one particular person will lose.

Important limitations of the comparison

SURMOUNT-5 provides stronger evidence than comparing two unrelated trials, but it still has limitations:

• It included adults with obesity who did not have diabetes.
• It was an open-label trial, meaning participants and researchers knew which medication was being used.
• It compared specific injectable doses over 72 weeks.
• Treatment was combined with diet and physical-activity counseling.
• The trial was funded by Eli Lilly, the manufacturer of tirzepatide.
• Trial participants are monitored more closely than many patients in routine practice.

The results therefore do not prove that every patient will lose more weight with tirzepatide.

How do these medications work?

Both medications imitate naturally occurring hormones involved in appetite, digestion and blood-sugar regulation.

Semaglutide

Semaglutide activates the glucagon-like peptide-1, or GLP-1, receptor. Its effects may include:

• Reducing appetite
• Increasing feelings of fullness after eating
• Slowing stomach emptying
• Reducing food intake
• Improving glucose-dependent insulin release

Tirzepatide

Tirzepatide activates both the GLP-1 receptor and the glucose-dependent insulinotropic polypeptide, or GIP, receptor.

This dual action is one possible explanation for the greater average weight reduction seen in clinical trials. However, stronger average efficacy does not eliminate the importance of tolerability, access and individual response.

Neither medication directly “melts” or targets a particular area of fat. Weight loss occurs primarily because people tend to feel less hungry, become full sooner and consume fewer calories over time.

Zepbound vs Mounjaro and Wegovy vs Ozempic

The active ingredients may be the same, but the brands and approved uses matter.

Tirzepatide brands

• Zepbound: Approved for chronic weight management in qualifying patients. It also has an indication for moderate-to-severe obstructive sleep apnea in adults with obesity.[2,3]
• Mounjaro: Approved to improve blood-sugar control in adults with type 2 diabetes when used with diet and exercise.

Semaglutide brands

• Wegovy: Approved for chronic weight management in qualifying patients. Wegovy injection also has an indication to reduce the risk of cardiovascular death, heart attack and stroke in certain adults with established cardiovascular disease and overweight or obesity.[4]
• Ozempic: Approved for adults with type 2 diabetes and specific related risk-reduction indications.

The dose, delivery system, labeling and insurance rules can differ between brands. Do not substitute one brand for another without instructions from a qualified prescriber.

Who may qualify for weight-loss medication?

Eligibility must be determined by a clinician. In general, injectable medications such as Zepbound and Wegovy may be considered for adults with:

• A body mass index of 30 or higher, or
• A body mass index of at least 27 plus a weight-related medical condition

Examples of weight-related conditions can include high blood pressure, abnormal cholesterol, type 2 diabetes, cardiovascular disease or obstructive sleep apnea.

BMI is an imperfect screening measurement. A responsible evaluation should also consider medical history, current medications, previous weight-management attempts, laboratory findings, pregnancy plans, eating-disorder history and potential contraindications.

These are prescription treatments for chronic weight management—not short-term cosmetic solutions.

When might tirzepatide be preferred?

A clinician might consider tirzepatide when:

• Maximizing average weight-loss potential is an important goal.
• The patient meets treatment criteria and has no contraindication.
• Insurance covers Zepbound or the patient can reliably obtain it.
• Previous treatment produced an inadequate response.
• Obesity occurs with moderate-to-severe obstructive sleep apnea.
• The patient can tolerate its gastrointestinal effects.

The head-to-head evidence favors tirzepatide for average weight reduction in adults with obesity without diabetes. Nevertheless, starting tirzepatide does not guarantee a better result for every person.

When might semaglutide be preferred?

A clinician might consider semaglutide when:

• Wegovy is covered while Zepbound is not.
• The patient previously responded well to semaglutide.
• Tirzepatide was not tolerated or is contraindicated.
• The patient has established cardiovascular disease and fits Wegovy’s cardiovascular risk-reduction indication.
• The prescriber determines that semaglutide better fits the complete medical picture.

A medication that produces slightly less weight loss in a trial may still be the better real-world choice if it is safer, covered, tolerated and consistently available for a particular patient.

Side effects of tirzepatide and semaglutide

The most common side effects of both medications involve the digestive system. These may include:

• Nausea
• Vomiting
• Diarrhea
• Constipation
• Abdominal discomfort
• Indigestion or reflux
• Reduced appetite

Symptoms are often most noticeable when treatment begins or after the dose is increased. Gradual dose escalation is intended to improve tolerability.

In SURMOUNT-5, gastrointestinal side effects were the most common adverse events in both groups. Most were mild to moderate and occurred during dose escalation.[1] The trial should not be interpreted as proof that one medication will always feel easier for an individual patient.

Practical ways to discuss side effects with your clinician

Depending on your situation, a clinician may recommend:

• Eating smaller meals
• Stopping when comfortably full
• Avoiding especially heavy or high-fat meals when nauseated
• Drinking enough fluid
• Increasing dietary fiber gradually when appropriate
• Remaining at a dose longer before escalating
• Delaying an increase when symptoms are still significant

Do not change your dose or dosing schedule without consulting the prescribing clinician.

Important warnings and precautions

Both medications carry a boxed warning concerning thyroid C-cell tumors observed in rodents. It is unknown whether either medication causes these tumors in humans.

They are contraindicated in people with:

• A personal or family history of medullary thyroid carcinoma
• Multiple Endocrine Neoplasia syndrome type 2
• A serious hypersensitivity reaction to the medication or its ingredients

Other potentially serious concerns include:

• Pancreatitis
• Gallbladder disease
• Dehydration and kidney injury
• Severe gastrointestinal reactions
• Hypoglycemia when combined with certain diabetes medications
• Allergic reactions
• Complications related to delayed stomach emptying during anesthesia or deep sedation

Tell your surgical and anesthesia teams that you take one of these medications before a procedure.

Weight-loss treatment is not appropriate during pregnancy. Discuss pregnancy, breastfeeding and plans to become pregnant with the prescribing clinician. Medication-specific instructions may be needed before a planned pregnancy.

Seek prompt medical care for severe or persistent abdominal pain, repeated vomiting, signs of dehydration, yellowing of the skin or eyes, difficulty breathing, facial swelling or another severe reaction.

Can you switch from semaglutide to tirzepatide?

Some patients switch because of inadequate weight loss, side effects, insurance coverage or a change in medical goals.

There is no single conversion dose that works for everyone. A safe plan depends on:

• The current medication and dose
• How long it has been used
• Previous side effects
• Other medications
• Blood-sugar levels
• The reason for switching

Do not take the two medications together unless a qualified prescriber has provided an appropriate plan. Zepbound should not be combined with another tirzepatide-containing product or a GLP-1 receptor agonist.[2]

Does a higher dose always produce better results?

Not necessarily.

Higher maintenance doses produced greater average weight loss in several trials, but they can also produce more side effects. The best dose is generally the lowest appropriate maintenance dose that provides meaningful benefit and acceptable tolerability.

Dose escalation should not become a race. Increasing too quickly can make nausea, vomiting, constipation or dehydration more difficult to manage.

What happens if the medication stops working?

Weight loss rarely follows a perfectly straight line. The rate commonly slows as body weight decreases, and temporary plateaus are expected.

Before labeling a medication a failure, a clinician may review:

• How long you have been at a therapeutic dose
• Whether doses are being taken consistently
• Total calorie and protein intake
• Physical activity and resistance training
• Sleep quality
• Constipation or fluid changes
• Medications that promote weight gain
• Thyroid, hormonal or metabolic conditions
• Whether the treatment goal is realistic

Do not increase the dose, shorten the interval between injections or combine medications independently.

Will the weight return after stopping treatment?

Weight regain is common after discontinuing anti-obesity medication. Appetite may increase when the medication’s effects wear off, while the biological pressures that promote weight regain remain.

This does not mean that treatment “failed.” Obesity is a chronic, relapsing medical condition, and many patients require long-term treatment. Before starting, discuss affordability, expected duration and what will happen if coverage changes.

Which one is better overall?

If the question is strictly which medication produced more average weight loss in the direct trial, the answer is tirzepatide.

If the question is which medication is best for a particular patient, the answer requires more context.

A thoughtful decision should consider:

1. Expected benefit
2. FDA-approved indications
3. Medical history and contraindications
4. Cardiovascular disease or obstructive sleep apnea
5. Diabetes and other medications
6. Side-effect tolerance
7. Insurance coverage and reliable access
8. Pregnancy plans
9. Ability to continue treatment long term
10. The patient’s preferences and goals

Frequently asked questions

Is tirzepatide the same as semaglutide?

No. Tirzepatide activates both GIP and GLP-1 receptors. Semaglutide activates the GLP-1 receptor.

Is Zepbound stronger than Wegovy?

In SURMOUNT-5, Zepbound’s active ingredient produced greater average weight loss than injectable semaglutide at the doses studied.[1] “Stronger” does not necessarily mean safer or more suitable for every patient.

Can I use Ozempic and Mounjaro together?

These medications should not be combined for weight loss. Combining incretin-based treatments can increase risk without established added benefit.

Which causes fewer side effects?

Both commonly cause gastrointestinal symptoms. Individual tolerability varies, so one person may do better with tirzepatide while another may tolerate semaglutide more easily.

How quickly will I lose weight?

Weight loss varies and usually develops over months. Initial doses are intended primarily for treatment initiation, not maximum weight loss. Results should be judged over an appropriate period under medical supervision.

Bottom line

Tirzepatide produced greater average weight loss than semaglutide in the 72-week SURMOUNT-5 head-to-head trial: 20.2% versus 13.7%.[1]

That is clinically meaningful evidence, but it does not make the treatment decision automatic. Semaglutide remains an effective option, and its cardiovascular indication may be particularly relevant for some patients. Tirzepatide may be especially relevant when greater average weight reduction or treatment of obesity-associated obstructive sleep apnea is a priority.

The best medication is one that is medically appropriate, tolerable, accessible and sustainable—with ongoing monitoring from a qualified healthcare professional.

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Medical review: Mark Aquino, MSN, APRN, FNP-C, board-certified family nurse practitioner.

Medical disclaimer: This article provides general educational information and is not individualized medical advice. Prescription weight-management medications require evaluation, prescribing and monitoring by a qualified healthcare professional. Never start, stop, combine or change the dose of a prescription medication based solely on online information.

References

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. doi:10.1056/NEJMoa2416394.
2. US Food and Drug Administration. FDA approves new medication for chronic weight management. Published November 8, 2023.
3. US Food and Drug Administration. FDA approves first medication for obstructive sleep apnea. Published December 20, 2024.
4. US Food and Drug Administration. FDA approves first treatment to reduce risk of serious heart problems specifically in adults with obesity or overweight. Published March 8, 2024.
5. 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. doi:10.1056/NEJMoa2206038.