Tirzepatide vs Wegovy: The Head-to-Head Weight Loss Comparison

This is the cleanest direct comparison in the GLP-1 weight-loss category. Both tirzepatide (sold as Zepbound for weight management) and Wegovy (semaglutide for weight management) are FDA-approved for the same indication, dosed weekly by subcutaneous injection, and prescribed for adults with obesity or overweight with at least one weight-related comorbidity. No off-label confusion to navigate, no different label to translate. Two on-label brands, two different molecules, two different manufacturers, two different price points.

The comparison breaks down on five dimensions: mechanism, average weight loss, side effects, cost, and cardiovascular evidence. We walk through each below, then close with how to think about choosing between them.

Wegovy is semaglutide, a GLP-1 receptor agonist. It is a synthetic version of GLP-1 (glucagon-like peptide-1), a hormone your gut releases after a meal. When the medication binds to the GLP-1 receptor, it slows gastric emptying, signals satiety to the brain, and stabilizes blood glucose.

Tirzepatide is a dual agonist. It binds both the GLP-1 receptor and the GIP receptor (glucose-dependent insulinotropic polypeptide). GIP is a second gut hormone that works in concert with GLP-1, and the dual activation amplifies effects on appetite suppression, gastric emptying, and insulin sensitivity. The dual-receptor mechanism is the structural reason behind tirzepatide’s larger average weight loss in clinical trials. For the underlying biology, see Harbor’s science of GLP-1 page.

The two registration trials and the head-to-head are the cleanest data we have.

STEP-1: Wegovy (semaglutide 2.4 mg)

The STEP-1 trial, published in the New England Journal of Medicine in 2021, enrolled 1,961 adults with overweight or obesity (without diabetes) and randomized them to semaglutide 2.4 mg weekly or placebo for 68 weeks. Mean body weight reduction was 14.9% on semaglutide compared with 2.4% on placebo. Eighty-six percent reached at least 5% weight loss and approximately 50% reached at least 15%. The full paper is available at nejm.org/doi/full/10.1056/NEJMoa2032183.

SURMOUNT-1: Zepbound (tirzepatide 15 mg)

The SURMOUNT-1 trial, published in the New England Journal of Medicine in 2022, enrolled 2,539 adults with overweight or obesity (without diabetes) and randomized them to tirzepatide 5 mg, 10 mg, 15 mg, or placebo for 72 weeks. Mean body weight reductions were 15.0% on 5 mg, 19.5% on 10 mg, and 20.9% on 15 mg, compared with 3.1% on placebo. Approximately 57% of participants at the highest dose lost 20% or more. The full paper is at nejm.org/doi/full/10.1056/NEJMoa2206038.

SURMOUNT-5: the direct head-to-head

SURMOUNT-5 is the first direct head-to-head trial of tirzepatide and Wegovy. The trial enrolled 751 adults with obesity (without diabetes) and reported that tirzepatide produced approximately 47% greater relative weight loss than semaglutide 2.4 mg at 72 weeks. The trial was conducted by Eli Lilly and reported in 2024.

[STAT BAR: Tirzepatide 15 mg — SURMOUNT-1 | 20.9% | 95%] [STAT BAR: Tirzepatide 10 mg — SURMOUNT-1 | 19.5% | 88%] [STAT BAR: Wegovy 2.4 mg — STEP-1 | 14.9% | 68%] [STAT BAR: Tirzepatide 5 mg — SURMOUNT-1 | 15.0% | 68%] [STAT BAR: Placebo — STEP-1 | 2.4% | 11%]

Visual: average weight loss in trials. Mean percentage body weight reduction at trial endpoint.

What the data adds up to

Tirzepatide produces approximately 5 to 6 percentage points more average weight loss than Wegovy at peak doses, which translates to roughly 40 to 47% greater relative weight loss in head-to-head trials. The advantage holds across patient subgroups, including by sex, baseline BMI, and age. Both medications produce clinically significant weight loss for the majority of patients who reach a therapeutic dose. The dose-escalation factor matters: real-world weight loss tends to be lower than trial averages because not every patient reaches the maximum tolerated dose.

Both medications share a gastrointestinal-dominant side effect profile. The mechanism that slows gastric emptying is the one that causes nausea. The differences come down to magnitude and timing.

Registration trial rates

• Nausea - Wegovy 43.9%, Zepbound 33.3%. Wegovy’s higher nausea rate is the most common reason for early discontinuation.
• Diarrhea - Wegovy 30.0%, Zepbound 22.0%.
• Vomiting - Wegovy 24.1%, Zepbound 19.0%.
• Constipation - Wegovy 24.2%, Zepbound 17.0%.

Tirzepatide’s lower side-effect rates in head-to-head comparison are likely a function of its longer titration schedule (six dose steps over 20 weeks) compared with Wegovy’s five steps over 16 weeks. Slower titration gives the body more time to adapt to each dose level.

Serious adverse events

Both medications carry a boxed warning for the risk of thyroid C-cell tumors observed in rodent studies. Risk in humans has not been established. Both are contraindicated in patients with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2. Pancreatitis and gallbladder disease are uncommon but documented adverse events on both. Serious adverse events occurred in 6.3% of tirzepatide recipients vs 6.7% on placebo in SURMOUNT-1; in 9.8% of semaglutide recipients vs 6.4% on placebo in STEP-1.

For symptom-by-symptom side effect management, see Harbor’s guide to managing tirzepatide side effects.

The single area where Wegovy outperforms tirzepatide today is cardiovascular outcomes evidence. The SELECT trial, published in 2023, randomized 17,604 adults with established cardiovascular disease and overweight or obesity (without diabetes) to Wegovy or placebo over a median of 39.8 months. Wegovy reduced the risk of major adverse cardiovascular events (cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke) by 20%.

This result extended Wegovy’s FDA indication in 2024 to include cardiovascular risk reduction in adults with established cardiovascular disease and overweight or obesity. It is also the basis for Medicare Part D coverage of Wegovy for that specific population.

Tirzepatide’s cardiovascular outcomes trial (SURPASS-CVOT) is ongoing, with results expected through 2027. Until that data is available, Wegovy is the GLP-1 with the strongest cardiovascular evidence base. For patients with established heart disease, this is a meaningful consideration.

Cost is the practical barrier for most patients without coverage. The list prices, savings programs, and compounded options form a four-layer landscape.

Brand list prices

• Zepbound - approximately $1,059 per month for autoinjector pens. Eli Lilly’s self-pay vial program offers single-dose vials at approximately $499 per month for selected lower doses (2.5 mg and 5 mg).
• Wegovy - approximately $1,349 per month for the single-use pen. Novo Nordisk offers a savings card for commercially insured patients that can reduce out-of-pocket cost depending on plan and a maximum monthly savings cap.

Insurance coverage

Coverage varies. Some commercial plans cover Wegovy and Zepbound for weight management with prior authorization, often requiring BMI documentation and step therapy. Medicare Part D was directed to cover Wegovy in 2024 for the SELECT cardiovascular risk-reduction indication, and Zepbound followed for the obstructive sleep apnea indication. State Medicaid programs that cover weight-loss medications are the exception.

Compounded options

Harbor offers compounded semaglutide at $99 per month and compounded tirzepatide at $149 per month, both with a 12-month results guarantee. Compounded preparations are not FDA-approved drug products. They are prepared by licensed 503A pharmacies under physician oversight. See our guide on brand vs compounded tirzepatide for the regulatory framework. Both options are HSA and FSA eligible.

Switching between Wegovy and tirzepatide is one of the most common transitions Harbor’s clinical team manages. The standard protocol is straightforward.

Wegovy to tirzepatide

1. Take the last Wegovy dose.
2. Wait one week.
3. Start tirzepatide at the 2.5 mg starting dose, regardless of the prior Wegovy dose.
4. Titrate every four weeks: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg.

Tirzepatide to Wegovy

1. Take the last tirzepatide dose.
2. Wait one week.
3. Start Wegovy at the 0.25 mg starting dose.
4. Titrate every four weeks: 0.25 mg, 0.5 mg, 1.0 mg, 1.7 mg, 2.4 mg.

Weight loss typically pauses or slows for the first one to two weeks during the switch and reaccelerates once the new medication reaches a therapeutic dose. Most patients find side effects equal to or milder than their original starting experience because the body has already adapted to incretin activity.

Both medications are reasonable choices for most adults with obesity. The differences are at the margin, and the margin is where the choice gets made.

Tirzepatide (Zepbound or compounded) is usually the right call when

• You have a weight-loss target of 20% or more.
• Your starting BMI is 35 or higher.
• You have insulin resistance, prediabetes, or co-existing type 2 diabetes.
• You have obstructive sleep apnea associated with obesity (Zepbound is FDA-approved for this indication).
• You have tried semaglutide before and plateaued before reaching your goal.

Wegovy (or compounded semaglutide) is usually the right call when

• You have established cardiovascular disease and obesity. The SELECT trial supports Wegovy specifically for this population.
• Your weight-loss target is in the 10 to 15% range.
• Cost-sensitivity is significant and the compounded option is the only affordable path. Compounded semaglutide at $99/mo is the lowest-cost route to a clinically meaningful weight loss.
• You want the medication with the longest post-market safety record. Semaglutide has been on the US market since 2017; tirzepatide since 2022.
• You have a history of significant GI sensitivity on prior GLP-1 attempts. Wegovy’s lower top dose can be easier for some patients to tolerate at peak.

About 60% of new Harbor members start on compounded semaglutide and 40% start on compounded tirzepatide. The match is based on starting BMI, weight-loss goal, cardiovascular history, prior GLP-1 experience, side-effect tolerance, and cost preference. The decision is made between member and clinician at the eligibility-quiz stage and re-visited as the program progresses.

About one in five members who start on semaglutide eventually switches to tirzepatide because of plateau or insufficient efficacy. The switch is managed through the patient portal without a price increase, and the 12-month results guarantee carries forward. Compare Harbor side-by-side with other GLP-1 programs on our compare page.