Tirzepatide vs. Semaglutide: How Do They Compare?

Tirzepatide and semaglutide are both once-weekly injections that lower appetite and blood sugar, but tirzepatide activates two gut hormone receptors (GIP and GLP-1) while semaglutide activates one (GLP-1). In SURMOUNT-5, the only large randomized trial to compare them directly for obesity, people on tirzepatide lost an average of 20.2% of their body weight over 72 weeks versus 13.7% on semaglutide. Semaglutide, however, has the longer safety record and, as of September 2026, the broader set of proven heart, kidney, and liver benefits. Both carry the same boxed warning about thyroid C-cell tumors.

Two molecules, four approved products

Much of the confusion around these medications comes from how they are packaged and approved. Each molecule is sold as one FDA-approved product for type 2 diabetes and a separate FDA-approved product for weight management, and the approved uses differ by product, not just by molecule. The active ingredient inside the pen is the same within each pair.

• Tirzepatide is available as the FDA-approved tirzepatide product for type 2 diabetes and the FDA-approved tirzepatide product for weight management, which also covers obstructive sleep apnea. Both are made by Eli Lilly.
• Semaglutide is available as the FDA-approved semaglutide product for type 2 diabetes and the FDA-approved semaglutide product for weight management (2.4 mg), which also covers cardiovascular risk reduction and a liver condition called MASH. Both are made by Novo Nordisk. Semaglutide also comes as a once-daily oral semaglutide tablet, with one version approved for type 2 diabetes and another for weight management.

The practical consequence is that a statement like "semaglutide is approved for heart protection" is only true for specific products, doses, and patient groups. The sections below spell out which is which, and for brevity they refer to each molecule's diabetes product and weight-management product. For a closer look at each medication on its own, see the pages on tirzepatide and semaglutide.

How the two drugs work differently

What they share: the GLP-1 pathway

GLP-1 (glucagon-like peptide-1) is a hormone your gut releases after you eat. The prescribing information for the weight-management tirzepatide product describes it as a physiological regulator of appetite and calorie intake. Drugs that mimic it, called GLP-1 receptor agonists, do three main things: they act on appetite centers in the brain so you feel full sooner and think about food less, they slow the rate at which your stomach empties, and they prompt the pancreas to release insulin only when blood sugar is elevated.

Semaglutide is a pure GLP-1 receptor agonist. It has been modified to resist breakdown and to bind to albumin, a blood protein, which is why a hormone that normally lasts minutes can be dosed once a week. The weight-management semaglutide label gives its elimination half-life as approximately 1 week, meaning it takes about 5 to 7 weeks after the last dose for the drug to clear your circulation.

What tirzepatide adds: the GIP pathway

GIP (glucose-dependent insulinotropic polypeptide) is a second gut hormone released after meals. Tirzepatide is a single molecule that activates both the GIP receptor and the GLP-1 receptor. According to its label, it carries a fatty acid chain that lets it bind albumin, giving it a half-life of approximately 5 to 6 days.

Tirzepatide is not an even split between the two pathways. A 2020 laboratory study by Lilly and academic researchers, using cell signaling experiments and isolated pancreatic islets, found that tirzepatide engages the GIP receptor more strongly than the GLP-1 receptor, and that at the GLP-1 receptor it signals in a "biased" way that differs from natural GLP-1. The authors proposed that this imbalance may help explain its effects. That is a mechanistic hypothesis built on cell work, not something proven in patients.

Why would adding GIP help? The honest answer

Nobody can yet say with certainty. The weight-management tirzepatide label is careful on this point: it states that both GIP and GLP-1 receptors are found in brain areas that regulate appetite, and that "nonclinical studies suggest" GIP may add to the regulation of food intake. Nonclinical means animal and laboratory studies. A 2020 scientific review by Lilly researchers noted that GIP's effects on fat tissue are still debated, while arguing that GIP appears to improve fat and sugar metabolism when paired with GLP-1's appetite effects.

One measurable difference has been shown in people: the weight-management tirzepatide label reports that tirzepatide increased insulin sensitivity in a clamp study (a precise laboratory test of how well the body responds to insulin) in patients with type 2 diabetes after 28 weeks. What is firmly established is the clinical result, covered next: in head-to-head trials, tirzepatide has produced more weight loss and more blood sugar lowering than semaglutide. The exact reason why is still being worked out. A sibling guide covers how tirzepatide's GIP and GLP-1 actions work in more depth.

SURMOUNT-5: the head-to-head weight loss trial

For years, comparisons between these drugs relied on lining up separate trials, which is unreliable because the trials enrolled different people under different conditions. SURMOUNT-5, published in the New England Journal of Medicine in 2025, removed that problem by randomizing people to one drug or the other.

How the trial was designed

SURMOUNT-5 was a phase 3b randomized trial of 751 adults with obesity who did not have type 2 diabetes. Participants were assigned 1:1 to the maximum tolerated dose of tirzepatide (10 mg or 15 mg) or the maximum tolerated dose of semaglutide (1.7 mg or 2.4 mg), injected once weekly for 72 weeks. The primary measure was the percent change in body weight at week 72. According to the American College of Cardiology's summary, it ran at 32 sites in the United States and Puerto Rico, the average age was 45, and 35% of participants were men.

What it found

Both differences in weight and waist size were statistically significant (P<0.001). Put in relative terms, tirzepatide produced roughly one and a half times the weight loss of semaglutide in this trial. In both groups the most common side effects were gastrointestinal, mostly mild to moderate, and occurred mainly while doses were being increased. The American College of Cardiology summary also noted that men lost less weight than women in both groups.

Limits you should know about

• It was open-label. Participants and doctors knew which drug was being given. Weight on a scale is an objective measure, but knowing your assignment can influence effort, persistence, and how side effects are reported.
• It was funded by Eli Lilly, the maker of tirzepatide. Industry funding is standard for trials of this size and does not invalidate the result, but it is worth knowing.
• It excluded people with type 2 diabetes, who lose less weight on both drugs.
• It compared the doses approved at the time. A higher 7.2 mg semaglutide dose was approved in 2026 and was not part of the trial.
• It measured weight, not health outcomes. It was not designed to show which drug prevents more heart attacks, and 72 weeks cannot answer long-term safety questions.

Does the result hold up in everyday practice?

A 2024 study in JAMA Internal Medicine looked at electronic health records from US health systems, a weaker form of evidence than a randomized trial because patients were not randomly assigned. After matching 18,386 adults with overweight or obesity who started either drug (in the versions labeled for diabetes), those on tirzepatide had lost more weight at 3, 6, and 12 months. The difference at 12 months was 6.9 percentage points, close to what SURMOUNT-5 later found.

That study also carries a sobering number: more than half of patients in both groups (55.9% on tirzepatide and 52.5% on semaglutide) had stopped their medication by the end of follow-up. Real-world persistence is far lower than in trials, and a drug you stop taking does not keep working.

How the placebo-controlled trials compare

Before SURMOUNT-5, each drug was tested against placebo in its own program: SURMOUNT for tirzepatide and STEP for semaglutide. These results are useful for understanding what each drug does, but comparing across them is less reliable than the head-to-head trial, because populations, trial lengths, and lifestyle programs differed.

What the averages hide

Averages conceal a wide spread. In SURMOUNT-1, 57% of people on the 15 mg dose lost 20% or more of their body weight, compared with 3% on placebo. In STEP 1, 50.5% of people on semaglutide lost 15% or more, compared with 4.9% on placebo. In both programs, a minority of participants lost relatively little despite taking the full dose. No test can currently predict in advance which group you will fall into.

Notice also the pattern in people with type 2 diabetes: both drugs produce meaningfully less weight loss in that group (about 13% to 15% with tirzepatide and about 10% with semaglutide 2.4 mg) than in people without diabetes.

The higher semaglutide dose narrows the gap

On March 19, 2026, the FDA approved a higher-dose version of the weight-management semaglutide product, a 7.2 mg dose of injectable semaglutide, for adults who have tolerated 2.4 mg for at least 4 weeks and for whom additional weight reduction is clinically indicated. In the STEP UP trial, 7.2 mg produced an average 18.7% weight loss at 72 weeks versus 15.6% with 2.4 mg. That moves semaglutide closer to tirzepatide's SURMOUNT-1 results, though the two have not been compared directly at these doses, so no one can say whether the gap has closed.

The higher dose brought more side effects. In STEP UP, gastrointestinal events were reported by 70.8% of people on 7.2 mg versus 61.2% on 2.4 mg, and dysesthesia (altered skin sensation, which the FDA describes as sensitivity, pain, or burning) affected 22.9% versus 6.0%. The FDA noted that these skin sensations typically resolved on their own or with a dose reduction.

Both drugs share the same weakness: regain after stopping

Neither medication produces a permanent change. In SURMOUNT-4, adults who had lost an average of 20.9% of their weight over 36 weeks on tirzepatide were randomized to continue or switch to placebo. Over the next 52 weeks, those who continued lost a further 5.5%, while those switched to placebo regained 14.0%. In STEP 4, people switched from semaglutide to placebo after 20 weeks regained 6.9% over the following 48 weeks, while those who continued lost another 7.9%. The guide on what happens when you stop taking semaglutide covers this in detail, and the same biology applies to tirzepatide.

Blood sugar control: the SURPASS-2 trial

If you have type 2 diabetes, the more relevant head-to-head trial is SURPASS-2, published in the New England Journal of Medicine in 2021. It randomized 1,879 adults with type 2 diabetes to tirzepatide 5 mg, 10 mg, or 15 mg, or to semaglutide 1 mg, for 40 weeks. Participants started with an average HbA1c (a 3-month average of blood sugar) of 8.28% and an average weight of 93.7 kg.

All three tirzepatide doses were statistically superior to semaglutide 1 mg for blood sugar lowering. The margin was modest at 5 mg (0.15 percentage points) and larger at 15 mg (0.45 percentage points). Clinically significant low blood sugar (below 54 mg per deciliter) was uncommon with either drug, reported in 0.2% to 1.7% of tirzepatide groups and 0.4% of the semaglutide group. Serious adverse events were reported in 5% to 7% of people on tirzepatide and 3% of those on semaglutide.

Two caveats matter. SURPASS-2 was open-label and funded by Eli Lilly. And the comparator was semaglutide 1 mg, not the 2 mg dose that the current label for the type 2 diabetes semaglutide product allows for people who need more glucose control. So SURPASS-2 shows tirzepatide beating a mid-range semaglutide dose, not its maximum diabetes dose.

Side effects compared

The shared profile

Because both drugs act on the GLP-1 receptor, their side effects are largely the same in kind: nausea, diarrhea, vomiting, constipation, abdominal pain, indigestion, burping, fatigue, and sometimes hair loss during rapid weight loss. The trials consistently report that these effects cluster around dose increases, which is why both drugs start low and step up no faster than every 4 weeks.

In both of the head-to-head trials, the rates of the most common stomach and bowel side effects were close. In SURPASS-2, nausea affected 17% to 22% of people on tirzepatide and 18% on semaglutide; diarrhea 13% to 16% versus 12%; and vomiting 6% to 10% versus 8%. The JAMA Internal Medicine records study likewise found similar rates of gastrointestinal adverse events between the two drugs.

What the prescribing information reports

The table below places the weight-management label figures side by side. Read it with caution: both labels explicitly warn that adverse reaction rates from one drug's trials cannot be directly compared with another's. The placebo columns show why. Placebo patients in the semaglutide weight-management trials reported nausea at twice the rate of placebo patients in the tirzepatide weight-management trials (16% versus 8%), which tells you the trials counted or elicited symptoms differently.

The fairest reading of all the evidence together is that tirzepatide is at least as well tolerated as semaglutide and possibly somewhat better, given that fewer people in SURMOUNT-5 stopped it for gastrointestinal reasons (2.7% versus 5.6%). It would be an overreach to say tirzepatide causes half the nausea. For a week-by-week view of how these effects typically rise and settle, see the semaglutide side effects timeline.

Serious warnings that apply to both

The warnings sections of the two weight-management labels, tirzepatide and semaglutide, are nearly identical.

• Boxed warning for thyroid C-cell tumors. In rodents, both drugs caused thyroid C-cell tumors at clinically relevant exposures. It is unknown whether either causes these tumors, including medullary thyroid carcinoma (MTC), in humans. Both are contraindicated if you have a personal or family history of MTC or have multiple endocrine neoplasia syndrome type 2 (MEN 2).
• Acute pancreatitis. Both labels instruct prescribers to stop the drug if pancreatitis is suspected. In the two main tirzepatide weight-management trials, confirmed pancreatitis occurred in 0.2% of patients on the drug and 0.2% on placebo.
• Gallbladder disease. In the weight-management labels, gallstones were reported in 1.1% of tirzepatide patients versus 1% on placebo, and in 1.6% of semaglutide injection patients versus 0.7% on placebo. Gallbladder inflammation was reported in 0.7% versus 0.2% with tirzepatide and 0.6% versus 0.2% with semaglutide. Rapid weight loss of any cause raises gallstone risk.
• Acute kidney injury from dehydration. Most reported cases followed significant vomiting or diarrhea.
• Low blood sugar, mainly when combined with insulin or a sulfonylurea. In the tirzepatide weight-management trial in people with type 2 diabetes, hypoglycemia occurred in 10.3% of patients also taking a sulfonylurea versus 2.1% of those who were not.
• Worsening of diabetic retinopathy in people with type 2 diabetes. In the SUSTAIN-6 trial of semaglutide, retinopathy complications were significantly more common with semaglutide than placebo (hazard ratio 1.76). The tirzepatide label warns that rapid improvement in glucose control has been linked with temporary worsening.
• Pulmonary aspiration during anesthesia. Both drugs slow stomach emptying, and there are rare reports of people inhaling stomach contents during general anesthesia or deep sedation despite fasting. Both labels tell patients to inform their care team before any planned procedure.
• Serious allergic reactions, including anaphylaxis and angioedema, have been reported with both.
• Severe gastroparesis. Neither drug is recommended if you have it.

Both drugs modestly raise resting heart rate: by an average of 1 to 3 beats per minute with tirzepatide and 1 to 4 beats per minute with semaglutide in the weight-management trials. One update worth knowing: earlier versions of both weight-management labels carried a warning about suicidal behavior and ideation. The current labels list that section as removed (February 2026 on both), after an FDA review found no increased risk.

Differences worth knowing

• Oral birth control. The tirzepatide labels advise people using oral hormonal contraceptives to switch to a non-oral method or add a barrier method for 4 weeks after starting and for 4 weeks after each dose increase, because delayed stomach emptying may reduce the pill's effectiveness. The weight-management semaglutide label carries no equivalent instruction; it notes that semaglutide 1 mg injection did not affect absorption of oral medications in pharmacology studies.
• Planning a pregnancy. Both labels say weight loss offers no benefit during pregnancy and may harm the fetus, and both drugs should be stopped when pregnancy is recognized if used for weight reduction. The weight-management semaglutide label adds a specific instruction to stop at least 2 months before a planned pregnancy because of semaglutide's long half-life.
• Injection site reactions were reported in 6% to 8% of patients on the weight-management tirzepatide product versus 2% on placebo.
• Track record. Injectable semaglutide's cardiovascular outcome trial in diabetes was published in 2016. Tirzepatide's first large pivotal trials were published in 2021 and 2022. Longer use in more people means more opportunity for rare problems to have surfaced.

When to seek urgent care

Whichever medication you take, the labels point to the same warning signs. Seek urgent medical attention for:

• Severe or persistent abdominal pain, especially if it spreads to your back, with or without vomiting (possible pancreatitis).
• Pain in the upper right abdomen, fever, yellowing of the skin or eyes, or clay-colored stools (possible gallbladder disease).
• Swelling of the face, lips, tongue, or throat, trouble breathing or swallowing, or a severe rash (possible serious allergic reaction).
• Vomiting or diarrhea severe enough that you cannot keep fluids down, or signs of dehydration such as very little urine or lightheadedness.
• Sudden changes in vision if you have diabetes.
• Shakiness, sweating, confusion, or fainting that could signal low blood sugar, particularly if you also take insulin or a sulfonylurea.

A lump or swelling in your neck, persistent hoarseness, or trouble swallowing should be reported to your prescriber promptly, as the labels list these as possible symptoms of thyroid tumors.

Heart, kidney, and liver outcomes: where the evidence stands

Weight and blood sugar are surrogate markers: numbers that stand in for the things you actually care about, such as heart attacks, strokes, kidney failure, and early death. This is where the two drugs differ most, and where semaglutide currently has the stronger evidence base.

Semaglutide's outcome trials

• SELECT (2023): 17,604 adults aged 45 or older with established cardiovascular disease and a BMI of 27 or higher, but no diabetes, received semaglutide 2.4 mg or placebo for an average follow-up of about 40 months. Cardiovascular death, heart attack, or stroke occurred in 6.5% on semaglutide versus 8.0% on placebo, a 20% relative reduction (hazard ratio 0.80). This is the basis for the cardiovascular indication on the weight-management semaglutide product.
• SUSTAIN-6 (2016): 3,297 adults with type 2 diabetes at high cardiovascular risk received semaglutide 0.5 mg or 1 mg or placebo for 104 weeks. The same composite outcome occurred in 6.6% versus 8.9% (hazard ratio 0.74).
• FLOW (2024): 3,533 adults with type 2 diabetes and chronic kidney disease received semaglutide 1 mg or placebo. The trial was stopped early after a planned interim analysis, with a median follow-up of 3.4 years. Major kidney disease events were 24% lower with semaglutide (hazard ratio 0.76), and death from any cause was 20% lower (hazard ratio 0.80).
• ESSENCE (2025): In an interim analysis of 800 adults with biopsy-confirmed MASH (metabolic dysfunction-associated steatohepatitis, a progressive form of fatty liver disease) and moderate or advanced scarring, 62.9% on semaglutide 2.4 mg had resolution of liver inflammation without worsening scarring, versus 34.3% on placebo.
• STEP-HFpEF (2023): In 529 adults with obesity and heart failure with preserved ejection fraction (a form of heart failure where the heart pumps normally but is stiff), semaglutide 2.4 mg improved a standard symptom score by 7.8 points more than placebo and improved 6-minute walking distance by about 20 meters more.

Tirzepatide's outcome trials

• SURPASS-CVOT (2025): 13,299 adults with type 2 diabetes and established cardiovascular disease were randomized to tirzepatide or dulaglutide, an older GLP-1 drug already proven to reduce cardiovascular events. There was no placebo group. Over a median of about 4 years, cardiovascular death, heart attack, or stroke occurred in 12.2% on tirzepatide versus 13.1% on dulaglutide (hazard ratio 0.92; 95.3% CI 0.83 to 1.01). Tirzepatide met the test for noninferiority, meaning it was at least as good, but it did not meet the test for superiority (P=0.09).
• SUMMIT (2025): In 731 adults with obesity and heart failure with preserved ejection fraction followed for a median of 104 weeks, cardiovascular death or a worsening heart failure event occurred in 9.9% on tirzepatide versus 15.3% on placebo (hazard ratio 0.62). The benefit came from fewer worsening heart failure events. Cardiovascular deaths were few and not reduced (8 with tirzepatide, 5 with placebo).
• SURMOUNT-OSA (2024): In two trials of adults with obesity and moderate-to-severe obstructive sleep apnea, tirzepatide reduced breathing interruptions by about 25 to 29 events per hour from a starting point of roughly 50, versus about 5 events per hour with placebo.

On August 28, 2026, the FDA approved the type 2 diabetes tirzepatide product to reduce the risk of major cardiovascular events in adults with type 2 diabetes at high risk, based on SURPASS-CVOT. The label itself states that superiority to dulaglutide was not established.

The gap that remains

As of September 2026, tirzepatide has no completed cardiovascular outcome trial in people with obesity who do not have diabetes, which is the population SELECT studied for semaglutide. That trial, SURMOUNT-MMO, is underway. According to its ClinicalTrials.gov record, it has enrolled 15,374 adults with a BMI of 27 or higher and either established cardiovascular disease or multiple risk factors, and its estimated primary completion date is October 2027.

It is reasonable to expect that a drug producing more weight loss, plus proven noninferiority to an established GLP-1 drug in diabetes, will also protect the heart in people with obesity. It is not yet proven. If preventing a second heart attack or stroke is your main reason for treatment and you do not have diabetes, this difference in evidence is a legitimate point to raise with your doctor.

What each product is FDA-approved for

The table below reflects the current prescribing information for each product, checked in September 2026. Approved indications change, so confirm with your prescriber or the current label.

A few notes on reading this table. The weight-management tirzepatide product's sleep apnea approval, granted on December 20, 2024, made it the first medication approved for that condition; the FDA noted that it improves sleep apnea by reducing body weight. The weight-management semaglutide product's MASH indication is an accelerated approval, which the label says may be contingent on a confirmatory trial verifying clinical benefit. And the oral semaglutide tablet for weight management is approved for weight reduction and cardiovascular risk reduction in adults, but its label notes it has not been studied for weight reduction in adults with type 2 diabetes.

How the dose schedules differ

Both drugs step up gradually to limit stomach side effects. Per the weight-management semaglutide label, the injection starts at 0.25 mg weekly and increases every 4 weeks through 0.5 mg, 1 mg, and 1.7 mg, reaching the 2.4 mg dose at week 17. Per the weight-management tirzepatide label, treatment starts at 2.5 mg weekly for 4 weeks, moves to 5 mg, and may then increase in 2.5 mg steps no sooner than every 4 weeks. The 2.5 mg dose is for starting only and is not an approved maintenance dose; 5 mg, 10 mg, and 15 mg are. Reaching 15 mg takes at least 20 weeks.

One practical difference: tirzepatide has three approved maintenance doses for weight management, and the lowest (5 mg) still produced an average 15.0% weight loss in SURMOUNT-1. Both labels tell prescribers to weigh treatment response and tolerability when choosing a maintenance dose. Decisions about your dose belong with your prescriber.

What about muscle loss?

Any substantial weight loss, by any method, includes some loss of lean mass (muscle, organ tissue, and water) along with fat. The concern is whether these drugs cause a disproportionate loss of muscle.

The best tirzepatide data come from a body-scan substudy of SURMOUNT-1, in which 160 participants had DXA scans (a low-dose X-ray that separates fat from lean tissue) at the start and at week 72. People on tirzepatide lost 33.9% of their fat mass and 10.9% of their lean mass. About 75% of the weight lost was fat and 25% was lean mass, and that ratio was the same in the placebo group, who lost far less weight overall. In other words, the proportion looked like ordinary weight loss, just more of it.

This was a small substudy, and DXA cannot measure muscle strength or function. No head-to-head trial has compared body composition changes between tirzepatide and semaglutide, so claims that one drug "spares muscle" better than the other are not supported by direct evidence. Because more total weight loss means more total lean mass lost, resistance training and adequate protein intake matter on either drug, and more so for older adults.

Who might suit which medication

There is no universally better drug. The choice is a clinical judgment made with your prescriber, and it usually turns on a handful of factors. These are the considerations the evidence supports.

Factors that point toward tirzepatide

• The largest average weight loss is the priority. SURMOUNT-5 is direct, randomized evidence that tirzepatide produces more weight loss than semaglutide at the doses compared.
• Type 2 diabetes with a need for more glucose lowering. SURPASS-2 showed greater HbA1c reduction than semaglutide 1 mg.
• Moderate-to-severe obstructive sleep apnea with obesity. The weight-management tirzepatide product is the only one of these four products with that indication.
• Difficulty tolerating semaglutide's stomach side effects. The evidence that tirzepatide is gentler is suggestive, not conclusive, and individual responses vary.

Factors that point toward semaglutide

• Established cardiovascular disease without diabetes. The weight-management semaglutide product has placebo-controlled outcome evidence (SELECT) and an FDA indication in this group. Tirzepatide's equivalent trial has not reported.
• Type 2 diabetes with chronic kidney disease. The type 2 diabetes semaglutide product has a kidney-protection indication based on FLOW.
• MASH with liver scarring. The weight-management semaglutide injection has an accelerated approval for it.
• Age 12 to 17 with obesity. The weight-management semaglutide injection is approved from age 12. The weight-management tirzepatide label states that safety and effectiveness have not been established in pediatric patients.
• Reliance on oral birth control, given the specific contraceptive advisory on tirzepatide labels.
• A strong preference to avoid injections. An oral semaglutide tablet for weight management exists. In its 64-week trial, the label reports a statistically significant weight reduction versus placebo; it has not been compared head-to-head with injectable tirzepatide.

Factors that apply equally to both

Neither drug is appropriate if you have a personal or family history of medullary thyroid carcinoma or MEN 2, or have had a serious allergic reaction to the drug, and neither is used for weight reduction during pregnancy. Neither should be combined with another GLP-1 medication. A history of pancreatitis, gallbladder disease, severe gastroparesis, or diabetic retinopathy warrants a careful conversation before starting either one. Both are intended to be used alongside a reduced-calorie diet and increased physical activity, and both work only for as long as you take them.

Insurance coverage and availability often end up deciding the question in practice. Those factors vary widely and are outside the scope of this guide.

Compounded and non-approved versions

During national shortages, compounding pharmacies were allowed to make copies of both drugs. That period has ended. The FDA determined that the tirzepatide shortage was resolved on December 19, 2024, and the semaglutide shortage on February 21, 2025, and its enforcement grace periods for compounders ended by March and May 2025 respectively. On April 30, 2026, the FDA proposed excluding semaglutide, tirzepatide, and liraglutide from the list of bulk substances that large outsourcing facilities may compound from, saying it found no clinical need given that approved versions are available. As of the FDA's last update reviewed for this article, that proposal had not been finalized.

The FDA states plainly that compounded drugs are not FDA approved, meaning the agency does not review them for safety, effectiveness, or quality. As of May 31, 2026, it had received 990 adverse event reports involving compounded semaglutide and more than 730 involving compounded tirzepatide. It has separately described hospitalizations tied to dosing errors with compounded semaglutide, and reports involving both drugs prescribed at doses above the approved label. It has also warned that salt forms such as semaglutide sodium and semaglutide acetate are different active ingredients from the one in approved products, and that counterfeit pens of the type 2 diabetes semaglutide product have been found in the US supply chain.

None of the trial results in this article apply to compounded or research-grade products, because none of those products were tested in the trials. The same caution applies even more strongly to newer investigational drugs sold online: a drug that is still in clinical trials cannot be legitimately purchased.

Myths versus realities

Myth: tirzepatide is just a stronger version of semaglutide

Reality: they are different molecules. Tirzepatide activates the GIP receptor in addition to the GLP-1 receptor, and laboratory work suggests it leans more heavily on GIP. It is a distinct drug with its own trials, label, and dosing, not a higher dose of the same thing. The milligram numbers are not comparable either: 15 mg of tirzepatide and 2.4 mg of semaglutide are each simply that drug's full weight-management dose in the trials discussed here.

Myth: tirzepatide causes fewer side effects, full stop

Reality: in both randomized head-to-head trials, the common gastrointestinal side effects occurred at similar rates. Fewer people stopped tirzepatide for stomach reasons in SURMOUNT-5, which hints at better tolerability, but that trial was open-label. The serious warnings are essentially identical.

Myth: more weight loss automatically means better health outcomes

Reality: probably, but not proven for every outcome. Semaglutide has placebo-controlled evidence of fewer heart attacks, strokes, and cardiovascular deaths in people with obesity and heart disease. Tirzepatide has shown it is at least as good as another proven GLP-1 drug in people with diabetes, and its outcome trial in obesity without diabetes is still running.

Myth: once you reach your goal weight you can stop

Reality: SURMOUNT-4 and STEP 4 both showed substantial regain after switching to placebo. Obesity behaves like a chronic condition, and both drugs are labeled for long-term use.

Questions to ask your doctor

1. Given my health history, is my main goal weight loss, blood sugar control, heart protection, or something else, and which drug has the best evidence for that goal?
2. Do I have any of the conditions that rule out both drugs, such as a family history of medullary thyroid cancer or MEN 2?
3. I have had gallstones, pancreatitis, or diabetic eye disease. How does that change the risk for me?
4. I take oral birth control. What does that mean if I start tirzepatide?
5. I take insulin or a sulfonylurea. How will my low blood sugar risk be managed?
6. How quickly will my dose increase, and what should I do if the side effects at a new dose are hard to tolerate?
7. How will we protect my muscle mass while I lose weight?
8. What is the plan for the long term, and what happens if I need to stop?
9. I have a surgery or a procedure with sedation coming up. Who needs to know I am on this medication?
10. If I am planning a pregnancy, when should the medication be stopped?

Bring a list of every medication and supplement you take. Because both drugs slow stomach emptying, the labels ask prescribers to take extra care with oral medications that have a narrow safety margin, such as warfarin.

This is general information, not medical advice. Whether a treatment is right for you is determined by a licensed provider after an evaluation.