Tirzepatide vs Semaglutide: A Comprehensive Comparison for Providers

Weight loss medications have undergone a sea change in the past several years. With the rise of incretin therapies, two names have emerged as leaders: tirzepatide and semaglutide. They share many similarities. The frequency with which we hear these two drug names bandied about, along with their brand names — Mounjaro/Zepbound and Ozempic/Wegovy, respectively — can lead to confusion.

Here, we will compare tirzepatide vs semaglutide and explain how each one works and their differences, while also highlighting potential future developments.

Tirzepatide vs Semaglutide At a Glance

How Do Tirzepatide and Semaglutide Compare in Effectiveness?

Both tirzepatide and semaglutide have been shown to be effective for weight loss in clinical trials and in practice. Hence their popularity. For simplicity, and because we are focusing on the weight loss indication for each, we will refer to the drugs by their brand names.

Zepbound Data as Reported by Lilly

The manufacturer’s language on the weight loss indication reads thus:

“Zepbound 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.”

At 72 weeks, patients taking Zepbound 15mg lost an average of 20.9% of their body weight; patients taking 10mg lost an average of 19.5%; and patients taking 5mg lost an average of 15%. Participants had a mean baseline starting weight of 226-231 lbs.

Wegovy Data as Reported by Novo Nordisk

The manufacturer’s language on the weight loss indication reads thus:

“Wegovy® (semaglutide) injection 2.4 mg 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 and pediatric patients aged 12 years and older with obesity and adults with overweight in the presence of at least one weight-related comorbidity.”

At two years, patients taking Wegovy showed a mean weight loss of 15% or 34 pounds, from a mean baseline BMI of 38.5. Studies also showed that one-third of patients taking Wegovy maintained weight loss of≥20% at two years.

A Head-to-Head Study

The Lilly-sponsored SURMOUNT-5 study compared weight loss with tirzepatide vs semaglutide. The results were published in The New England Journal of Medicine in May 2025.

SURMOUNT-5 was a phase 3b, open-label, controlled trial, comparing weight loss outcomes in adult patients taking tirzepatide or semaglutide. The primary endpoint was the percent change in weight from baseline at 72 weeks. Participants lost an average of 50.3 lbs. or 20.2% of their weight on Zepbound or 33lb or 13.7% on Wegovy.

What Are the Differences in How Tirzepatide and Semaglutide Work?

Both medications work by mimicking incretins. The gastrointestinal system secretes these hormones following nutrient intake. They facilitate digestion and subsequent absorption and metabolism of nutrients from food. Research is still working to fully understand the role incretins play in overall health.

Incretins have been studied for more than 140 years, but advancements in the 2010s and 2020s highlight two: GIP (glucose-dependent insulinotropic polypeptide), from the upper gut, and GLP-1 (glucagon-like peptide-1), from the lower gut. They signal the pancreas to secrete more insulin, which helps lower blood sugar. The effects of these hormones are diminished in people with type 2 diabetes.

GIP and GLP-1 also help regulate food intake by stimulating neurons in the brain’s satiety center. In addition, they have effects on adipose cells, bone, and the cardiovascular system. This is why these medications, initially developed to treat diabetes, have proved effective for treating obesity, cardiovascular disease, and even obstructive sleep apnea. Research into these and other applications continues to proliferate.

GIP-1 and GIP

Semaglutide activates the GLP-1 receptor, prompting an increase in glucose-dependent insulin secretion. It slows food movement through the digestive tract, making the person feel fuller for longer, helping the liver regulate sugar production, and reducing food cravings.

Other GLP-1 receptor agonists include liraglutide (Saxenda) and dulaglutide (Trulicity). Both are indicated to treat type 2 diabetes.

Tirzepatide is a dual agonist, acting on both GLP-1 and GIP. Its proponents report that adding GIP provides a more comprehensive approach to managing diabetes and obesity.

Both medications are shown to help patients lose weight in combination with diet and exercise. Some patients also report that the treatment helps to quiet “food noise,” or intrusive thoughts about food and eating, a struggle for many who have lived with overweight for a long time.

Triple-receptor agonists — or triagonists — in development target GLP-1, GIP, and glucagon receptors.

Administration and Ongoing Development

Both tirzepatide and semaglutide are administered at home by subcutaneous injection, starting at a low dose and titrating up to a maintenance dose. Fear or discomfort about needles may be a barrier to some patients who meet the criteria for these drugs.

In September 2025, clinical research was published on weight loss for two oral incretin therapies: an oral version of semaglutide and Orforglipron, also a GLP-1 receptor agonist. The former showed a mean weight loss of 13.6%, while the latter showed a mean weight loss of 11.2%. Both showed gastrointestinal adverse events consistent with GLP-1 receptor agonists. Novo Nordisk received approval for Wegovy tablets in December 2025.

How Do the Side Effects of Tirzepatide and Semaglutide Compare?

Side effects of weight loss medications in this class have grabbed headlines. Both medications have similar common side effects, namely gastrointestinal issues, including nausea, vomiting, pancreatitis, and diarrhea.

Patients may discontinue treatment due to the inability to tolerate these side effects. For example, in one cohort study of 125,474 patients (without type 2 diabetes) who initiated GLP-1s, 46.5% discontinued use within one year.

Other side effects include bone remodeling and kidney and thyroid disorders. However, evidence for the causality of pancreatitis with either semaglutide or tirzepatide remains controversial. Both drugs carry a boxed warning regarding the risk of thyroid C-cell tumors. Both Zepbound and Wegovy have depression listed as a potential side effect.

Does Insurance Coverage Differ Between Tirzepatide and Semaglutide?

Insurance coverage for weight loss medications varies and is currently in a state of flux. The manufacturers of these medications offer tools on their websites or via phone that can help patients understand whether they are covered and how to get assistance.

Commercial and Employer-Sponsored Insurance Plans

Whether your patient works for a government entity or a private employer, they will need to check with their specific healthcare plan. Coverage for weight loss medications varies from employer to employer and plan to plan. The same is true for individual self-pay plans. Affordable Care Act plans typically do not cover them.

Health plans do usually cover these medications for other indications, such as type 2 diabetes or, in the case of Zepbound, obstructive sleep apnea.

Patients whose plans do cover these medications for weight loss indications may still need you to submit a prior authorization request on their behalf.

Government Insurance Plans

As of this writing in late 2025, Medicare does not cover weight loss medications. However, starting in mid-2026, Medicare will begin covering GLP-1s and GLP-1/GIPs with copays as low as $50 a month.

Some Medigap and Medicare Advantage plans offer coverage, so patients should check with their individual plans.

Medicaid coverage varies by state, and changes are anticipated for 2026, so you or your patient will need to monitor the preferred drug list (PDL) in your state.

Savings and Direct Purchase Options

Both Lilly and Novo Nordisk offer savings cards for people with commercial insurance that does not cover weight loss medications. Direct patients to check each manufacturer’s website to enroll in their respective savings card program.

Additionally, both manufacturers sell these medications directly to patients with a prescription, which may save them money compared to purchasing them at the pharmacy. Again, direct them to the websites to learn what steps they need to take.

FAQs

Is a "washout period" required when switching a patient from semaglutide to tirzepatide?

There are different reasons a patient may want to switch between semaglutide and tirzepatide. It might be a change in insurance coverage or the inability to tolerate one of the medications. A washout period is not required, but may be recommended for certain patients. If they have struggled with side effects with the first medication, they may benefit from a one- to two-week break before starting the new one.

What is the recommended starting dose of tirzepatide for a patient already on the maximum dose of semaglutide (2.4 mg)?

Any patient starting either tirzepatide or semaglutide will start at the lowest dose and titrate up, regardless of whether they have previously taken an incretin medication.

Can a patient switch directly from tirzepatide to semaglutide if they experience intolerance?

A study published in 2024 looked at people switching from a GLP-1 receptor agonist to tirzepatide 5mg. 13.2% of participants developed gastrointestinal events on tirzepatide, but overall, the participants experienced greater weight reduction. So there is no guarantee that a patient will or will not experience side effects on either form of treatment.

Does insurance typically require a new prior authorization when switching between these agents?

Many insurance plans do require prior authorization for incretin-based weight loss medicines. Some plans may require trying a patient on a particular medication before trying the other one. When switching from one to the other, patients will need to check with their insurance provider or employer to find out what documentation is required for prior authorization.