For many Americans struggling to lose weight, powerful new medications are changing the game. With roughly 40% of U.S. adults living with obesity, according to the Centers for Disease Control and Prevention, the demand for effective treatments has never been higher. Two groundbreaking “weight loss shots” — semaglutide (known by brand names like Ozempic or Wegovy) and tirzepatide (Mounjaro or Zepbound) — have emerged as highly effective weight loss medications.
Both semaglutide and tirzepatide work by mimicking natural gut hormones to help manage Type 2 diabetes and promote significant weight loss. But they work in slightly different ways. The difference in how they target the body’s hunger and fullness signals is key to understanding the potential weight loss differences between them.
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How They Work: GLP-1 and GIP Hormones
Semaglutide is a single-action drug, mimicking the GLP-1 (glucagon-like peptide-1) gut hormone. Tirzepatide, on the other hand, is a dual-action drug, mimicking both GLP-1 and GIP (glucose-dependent insulinotropic polypeptide).
Both GIP and GLP-1 are known as incretin hormones. They are secreted from the gut in response to food. These hormones regulate appetite, blood sugar and digestion.
What is GLP-1?
GLP-1 is a natural hormone released after meals, and it does a lot of good:
— Helps you feel full longer: It slows down how quickly food leaves your stomach.
— Curbs hunger: It signals to your brain that you are full, which helps reduce cravings and overall food intake.
— Manages blood sugar: It boosts insulin production and lowers glucagon (a hormone that raises blood sugar), making it particularly helpful for people with diabetes.
What is GIP?
GIP is another gut hormone released in response to food. Like GLP-1, GIP helps increase insulin and decrease glucagon. Research suggests that GIP also plays a role in burning energy and may even help prevent fat storage.
The power of 2: GIP and GLP-1
GIP and GLP-1 are believed to work together to be more effective. Experts suggest they act synergistically to increase the feeling of fullness (satiety), reduce how much you eat and boost weight loss.
According to Dr. Eiriny Eskander, a dual board-certified endocrinologist and internal medicine physician who works at Diabetes and Endocrine Specialists in Encino, California, this dual-action mechanism creates a more powerful and effective agent, leading to greater weight loss.
Since tirzepatide mimics both GLP-1 and GIP, it is more effective at reducing weight.
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Comparing Semaglutide and Tirzepatide
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Efficacy: Key Weight Loss Findings
Studies show both semaglutide and tirzepatide can lead to significant weight loss when combined with diet and exercise, with tirzepatide having higher average weight loss result. Here are the highlights of how they compare:
— Semaglutide (like Wegovy): In the STEP-1 trial, people who were overweight or had obesity (without diabetes) and took once-weekly semaglutide lost an average of 15% of their body weight over 68 weeks. This was much better than the 2.4% lost by the placebo group. Participants also saw improvements in heart health markers like blood pressure and cholesterol levels. In separate studies, the semaglutide pill was found to be as effective as the injection. People who took 25 mg of semaglutide orally lost approximately 14% of their body weight, compared with just 2% with a placebo.
— Tirzepatide (like Zepbound): The Surmount-1 trial, involving people with obesity or who were overweight (without diabetes), found that once-weekly tirzepatide led to an even greater weight loss. Depending on the dose (5 mg, 10 mg or 15 mg), participants lost an average of 15% to 21% of their body weight after 72 weeks. All doses outperformed the placebo.
Both medications are effective weight-loss tools. However, in their respective trials, tirzepatide demonstrated a potentially higher maximum average weight loss (up to 21%) compared to semaglutide (up to 15%).
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Comparison of Side Effects and Safety
Semaglutide and tirzepatide can cause similar side effects, which are usually mild. Clinical trials of semaglutide and clinical trials of tirzepatide indicate that tirzepatide may be better tolerated. Side effects occurred more frequently among participants receiving semaglutide.
The most common side effects associated with GLP-1s are gastrointestinal-related. During clinical trials, these side effects were mostly mild to moderate and temporary, typically occurring during dosage increases.
During the Surmount-5 clinical trial, which compared semaglutide to tirzepatide for weight loss, more patients who took semaglutide discontinued treatment due to side effects than those who took tirzepatide. Also, people who received semaglutide were more likely to have vomiting.
“People are very worried about potential side effects, but even at the highest dose, about 95% to 96% of patients can tolerate the medicine,” adds Dr. Disha Narang, an endocrinologist and director of obesity medicine at Endeavor Health in Chicago.
Eskander says that at her practice, she finds that patient better tolerate tirzepatide.
[READ: What to Know About the New Wegovy Pill]
Serious side effects
GLP-1s can cause more serious side effects, though these are less common.
Rapid weight loss, along with slowed digestion, can increase the risk of gallbladder inflammation and gallstones. This risk is increased at higher doses and during long-term treatment. Gallstones can block the gallbladder opening, the cystic duct or the bile ducts. This causes bile to back up into the gallbladder, causing inflammation, pain, nausea and vomiting. This can lead to complications such as pancreatitis and sepsis.
People taking semaglutide and tirzepatide have developed acute pancreatitis, a sudden inflammation of the pancreas, which can lead to organ dysfunction, organ failure and even death. Although pancreatitis rates were low in clinical trials, individuals with a history of pancreatitis should avoid GLP-1 receptor agonists.
All GLP-1s, including semaglutide and tirzepatide, carry boxed warnings regarding the risk of thyroid C-cell tumors, also known as medullary thyroid cancer. Boxed warnings are assigned by the Food and Drug Administration and highlight serious drug-related risks.
In clinical studies, both semaglutide and tirzepatide caused tumors in thyroid C-cells of rats. These tumors were more likely to occur with high-dose, long-term treatment. Results are inconclusive as to whether this increases the risk in humans. However, because of this possible risk, people with a personal or family history of medullary thyroid carcinoma and those with multiple endocrine neoplasia syndrome type two should not use GLP-1 medications.
Also, those with gastroparesis, or delayed stomach emptying, should avoid GLP-1 medications as they could worsen this condition.
Eskander says that she has noticed that GLP-1 medications can also cause acid reflux, and she avoids prescribing GLP-1s in those with severe acid reflux or gastrointestinal conditions.
[READ: Best Medicines for Heartburn, Nausea and Digestive Issues]
Which One Is Right for You?
When choosing a weight-loss medication, it is important to have a detailed discussion with your health care provider. Together, you should review your current medications, health history and weight-loss goals to develop a treatment plan.
Narang adds that she has seen significant success with either medication, and it is not a one-size-fits-all approach.
Choosing between semaglutide (Wegovy, Ozempic, Rybelsus) and tirzepatide (Zepbound, Mounjaro) for weight management involves practical considerations beyond just efficacy. Here’s a breakdown of key factors to help you and your doctor decide:
Administration: injection vs. pill
— Both drugs offer a once-weekly injection in the abdomen, thigh or upper arm, requiring site rotation and refrigeration.
— If you prefer a pill over an injection, the daily Wegovy pill is currently your only (non-compounded) option, but it comes with strict timing requirements. A daily pill version of Zepbound is expected to come to market later in 2026. The pill does not require refrigeration.
Dosage
— Both medications are started at a low dose and gradually increased (titrated) typically every four weeks to minimize side effects.
— Tirzepatide has more strengths, meaning more steps to reach the highest dose, which could mean a slower adjustment if you need the maximum strength
Cost and Coverage
— GLP-1 medications are expensive, and many insurance plans do not cover them, often requiring prior authorization if they do. Coverage is more likely if you have a condition like Type 2 diabetes or cardiovascular disease.
— Without insurance, tirzepatide is generally more expensive than semaglutide. The pill version of semaglutide offers the lowest entry price.
FAQs Comparing Semaglutide and Tirzepatide
Which drug causes more weight loss?
According to clinical trials, tirzepatide results in greater weight loss. At the maximum dose of tirzepatide, participants lost an average of 21% of their body weight, compared with 15% with semaglutide.
Is one injection more painful than the other?
In the Surmount-5 trial, which was a comparison of tirzepatide to semaglutide for weight loss, more people experienced injection site reactions with tirzepatide compared to semaglutide. If you are worried about the pain associated with the injections, semaglutide is also available as an oral pill.
Can I switch from semaglutide to tirzepatide?
Yes, you can switch from semaglutide to tirzepatide, but only under the direct care of your health care provider. Your provider will determine the new starting dose and schedule. Some people switch medications due to experiencing bothersome side effects, not meeting their weight loss goal, insurance coverage and price.
Are the side effects the same for both medications?
Both semaglutide and tirzepatide cause similar side effects. The most common side effects from these medications are gastrointestinal-related and include nausea, vomiting, constipation and diarrhea.
Why is tirzepatide called a “dual agonist”?
Tirzepatide is classified as a dual agonist because it activates two receptors: GIP and GLP-1. GIP and GLP-1 are hormones secreted by the intestines that regulate blood glucose, appetite and digestion. When used together, they produce a greater effect than when GLP-1 is used alone.
How much do semaglutide (Wegovy/Ozempic) and tirzepatide (Zepbound/Mounjaro) cost without insurance?
The price of these medications varies by pharmacy, location and strength. The manufacturers of semaglutide and tirzepatide offer direct-to-consumer pricing through their savings programs. The pricing is as follows:
— Mounjaro: $499 per month
— Ozempic: $349 to $499 per month
— Wegovy: $199 to $299 per month for the pill, $349 per month for the injections
— Zepbound: $499 per month
Bottom Line
Semaglutide and tirzepatide are both highly effective weight-loss medications. Both slow digestion and reduce appetite and cravings. They also share similar side effects
Clinical trials have shown that tirzepatide produces greater weight loss than semaglutide, but for those paying out of pocket, it is more expensive. Semaglutide can reduce the cardiovascular risk in people with cardiovascular disease and provides benefits for kidney and liver health. Tirzepatide can improve sleep apnea, but it is only available as an injection, whereas semaglutide is also available as a convenient daily tablet.
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Semaglutide vs. Tirzepatide for Weight Loss originally appeared on usnews.com