Semaglutide vs. tirzepatide: choosing the right GLP-1

They are not exactly the same medication

Semaglutide and tirzepatide are two of the most widely discussed medications for weight loss. Both can help people lose a meaningful amount of weight when used with nutrition, physical activity, and clinical support. Both are taken on a schedule that gradually increases the dose. Both can cause side effects, especially gastrointestinal symptoms. And both should be prescribed and monitored by a licensed clinician. But they are not exactly the same medication. Semaglutide is a GLP-1 receptor agonist. Tirzepatide is a dual GIP and GLP-1 receptor agonist. That difference may help explain why tirzepatide has shown greater average weight loss in several studies, including a direct head-to-head trial. But "more weight loss on average" does not automatically mean it is the right choice for every patient. The right medication depends on your health history, goals, side-effect tolerance, cost, availability, contraindications, and your clinician's judgment.

First, what are GLP-1 medications?

GLP-1 stands for glucagon-like peptide-1, a hormone involved in appetite, digestion, and blood sugar regulation. GLP-1 receptor agonists mimic some of GLP-1's effects. They can help people feel fuller sooner, reduce hunger, slow stomach emptying, and improve blood sugar control. Semaglutide is the active ingredient in Wegovy, which is FDA-approved for chronic weight management, and Ozempic, which is FDA-approved for type 2 diabetes. Wegovy's FDA label describes it as a GLP-1 receptor agonist used with reduced-calorie diet and increased physical activity for long-term weight reduction in adults with obesity, adults with overweight and at least one weight-related condition, and adolescents age 12 and older with obesity. The label also includes cardiovascular risk reduction in adults with established cardiovascular disease and either obesity or overweight. Tirzepatide is the active ingredient in Zepbound, which is FDA-approved for chronic weight management, and Mounjaro, which is FDA-approved for type 2 diabetes. Zepbound's FDA label describes tirzepatide as a glucose-dependent insulinotropic polypeptide, or GIP, receptor and GLP-1 receptor agonist. It is indicated with 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 and at least one weight-related condition. The label also includes treatment of moderate to severe obstructive sleep apnea in adults with obesity.

How semaglutide works

Semaglutide activates the GLP-1 receptor. In practical terms, that can help reduce appetite, increase fullness, slow gastric emptying, and improve glucose regulation. For weight loss, the best-known semaglutide trial is STEP 1. In adults with overweight or obesity without diabetes, once-weekly semaglutide 2.4 mg plus lifestyle intervention led to an average body weight change of -14.9% at 68 weeks, compared with -2.4% with placebo. That is a large average effect compared with older weight-loss medications. But individual responses vary. Some people lose substantially more than average, while others lose less or stop because of side effects.

How tirzepatide works

Tirzepatide activates both the GIP and GLP-1 receptors. It is sometimes called a "dual agonist." The GIP component is one reason tirzepatide is often discussed separately from older GLP-1-only medications. In the SURMOUNT-1 trial, adults with obesity or overweight without diabetes received tirzepatide or placebo for 72 weeks. Average weight change was -15.0% with 5 mg, -19.5% with 10 mg, and -20.9% with 15 mg, compared with -3.1% with placebo. Gastrointestinal side effects were the most common adverse events and were usually mild to moderate, especially during dose escalation. Those results are why tirzepatide is often seen as one of the most effective weight-loss medications currently available.

Which one leads to more weight loss?

On average, tirzepatide appears to produce greater weight loss than semaglutide at commonly studied obesity doses. The strongest evidence is the SURMOUNT-5 head-to-head trial, published in The New England Journal of Medicine in 2025. It compared tirzepatide with semaglutide in adults with obesity but without type 2 diabetes. The PubMed record describes it as a phase 3b, open-label, controlled trial comparing the two medications directly. Earlier observational research also found that tirzepatide was associated with greater weight loss than semaglutide among adults with overweight or obesity, though observational studies are not as strong as randomized controlled trials because treatment groups can differ in important ways. A fair summary is: tirzepatide tends to produce more weight loss on average, but semaglutide remains highly effective and may be the better choice for some patients.

Why someone might choose semaglutide

Semaglutide may be a good fit when a clinician wants a medication with a longer track record in GLP-1 use, specific cardiovascular evidence, or a treatment option that matches a patient's insurance coverage and medical history. Wegovy's FDA label includes an indication to reduce the risk of major adverse cardiovascular events in adults with established cardiovascular disease and either obesity or overweight. Semaglutide may also be preferred if someone has previously tolerated it well, has access to it through insurance, or is looking for a medication with substantial long-term obesity data. In STEP 5, semaglutide 2.4 mg produced weight loss of about 15% at two years in adults with overweight or obesity.

Why someone might choose tirzepatide

Tirzepatide may be a good fit when the main clinical goal is greater average weight loss, assuming the patient is an appropriate candidate and tolerates the medication. The SURMOUNT-1 results showed average weight loss above 20% at the higher studied doses, and Zepbound's approved maintenance doses for weight reduction are 5 mg, 10 mg, or 15 mg once weekly. Tirzepatide may also be relevant for patients with obesity and moderate to severe obstructive sleep apnea, because Zepbound's FDA label includes that indication. Again, that does not mean tirzepatide is automatically "better." It means the expected weight-loss effect may be larger on average, while the right choice still depends on the individual.

Side effects: what to expect

The most common side effects for both medications are gastrointestinal. These may include nausea, vomiting, diarrhea, constipation, abdominal discomfort, reduced appetite, reflux, or bloating. Side effects are often most noticeable when starting treatment or increasing the dose. That is why these medications are usually titrated gradually rather than started at the highest dose. Both medications also carry important warnings and precautions. Wegovy's label lists warnings including acute pancreatitis, acute gallbladder disease, hypoglycemia when used with insulin or insulin secretagogues, acute kidney injury due to volume depletion, severe gastrointestinal adverse reactions, hypersensitivity reactions, diabetic retinopathy complications in patients with type 2 diabetes, increased heart rate, and pulmonary aspiration during anesthesia or deep sedation. Zepbound's label lists warnings including severe gastrointestinal adverse reactions, acute kidney injury due to volume depletion, acute gallbladder disease, acute pancreatitis, hypersensitivity reactions, hypoglycemia when used with insulin or insulin secretagogues, diabetic retinopathy complications in patients with type 2 diabetes, suicidal behavior and ideation, pulmonary aspiration during anesthesia or deep sedation, and instructions not to share pens between patients.

Who should not take these medications?

Both semaglutide and tirzepatide carry a boxed warning related to thyroid C-cell tumors observed in rodents. It is unknown whether these drugs cause medullary thyroid carcinoma, or MTC, in humans. Wegovy is contraindicated in people with a personal or family history of MTC or Multiple Endocrine Neoplasia syndrome type 2, also called MEN 2. Zepbound has the same type of contraindication: it should not be used in people with a personal or family history of MTC or in patients with MEN 2. These medications are also generally not used during pregnancy. Wegovy's label advises discontinuing semaglutide at least two months before a planned pregnancy because of its long half-life. Zepbound's label states that it may cause fetal harm and should be discontinued when pregnancy is recognized. It also advises people using oral contraceptives to switch to a non-oral method or add a barrier method for four weeks after starting tirzepatide and for four weeks after each dose escalation, because tirzepatide can affect absorption of oral medications. A clinician should review personal history of pancreatitis, gallbladder disease, kidney disease, diabetes medications, diabetic retinopathy, gastrointestinal disease, pregnancy plans, current medications, and prior medication reactions before prescribing.

What about compounded versions?

Some patients use compounded semaglutide or compounded tirzepatide when FDA-approved branded medications are unavailable, not covered, or unaffordable. Compounding can be legal in certain circumstances, but patients should be careful. The FDA has warned about fraudulent compounded semaglutide and tirzepatide products, dosing errors, adverse events, and products labeled with pharmacies that did not actually compound them. The FDA advises patients to know the source of their medicine, check labels carefully, and ensure the medication is prescribed by a licensed healthcare provider and provided by a licensed pharmacy. The FDA has also stated that some compounded semaglutide products may use salt forms such as semaglutide sodium or semaglutide acetate, which are different active ingredients from the active ingredient used in approved semaglutide drugs. The practical takeaway: avoid research-use products, peptide websites, counterfeit products, or anything not prescribed and dispensed through appropriate medical and pharmacy channels.

How to choose between semaglutide and tirzepatide

The decision should be individualized. In a real clinical visit, a provider may weigh questions like:

• What is the primary goal? If the main goal is the greatest average weight loss, tirzepatide may be considered. If cardiovascular risk reduction in a patient with established cardiovascular disease is a key factor, semaglutide may be especially relevant because Wegovy has that labeled indication.
• What does the patient tolerate? The best medication is not the one with the highest average weight loss in a trial. It is the one the patient can safely and consistently use.
• What does insurance cover? Coverage can determine whether a medication is realistic long term. Stopping GLP-1 therapy often leads to weight regain for many patients, so affordability and continuity matter.
• What other conditions are present? Type 2 diabetes, cardiovascular disease, sleep apnea, kidney disease, gallbladder history, pregnancy plans, and current medications can all affect the decision.
• What has the patient tried before? If someone has already used semaglutide successfully, switching may not be necessary. If someone had limited response or poor tolerance, a clinician may consider another option.

The bottom line

Semaglutide and tirzepatide are both effective medications for weight management when used appropriately with lifestyle changes and medical supervision. Semaglutide is a GLP-1 receptor agonist with strong evidence for weight loss and specific cardiovascular risk-reduction labeling in adults with established cardiovascular disease and overweight or obesity. Tirzepatide is a dual GIP/GLP-1 receptor agonist that generally produces greater average weight loss in obesity trials and is also approved for adults with obesity and moderate to severe obstructive sleep apnea. Neither medication is "one size fits all." The right choice is the one that matches your health profile, goals, safety considerations, access, and long-term plan.