semaglutide vs tirzepatide: how they compare

Both are once-weekly injections that quiet appetite and slow how fast your stomach empties, so you feel full sooner and eat less without forcing it. The difference is the receptors they act on. Semaglutide is a GLP-1 receptor agonist. It mimics one gut hormone (GLP-1) that signals fullness to the brain. Tirzepatide is a dual agonist: it acts on GLP-1 and a second hormone receptor, GIP, at once.

That second pathway is the leading theory for why tirzepatide tends to produce more weight loss in studies, the two hormone signals together appear to suppress appetite more than GLP-1 alone. Brand names can be confusing: Ozempic and Wegovy are both semaglutide (Ozempic for diabetes, Wegovy for weight), while Mounjaro and Zepbound are both tirzepatide. Same molecule, different label and approved use.

In the STEP 1 trial, adults with overweight or obesity (without diabetes) taking semaglutide 2.4 mg plus lifestyle support lost about 14.9% of their body weight over 68 weeks, compared with 2.4% on placebo. In the SURMOUNT-1 trial, adults taking tirzepatide lost roughly 16% to 22.5% of their body weight over 72 weeks, depending on dose, about 20.9% on the 10 mg dose and 22.5% on the highest dose.

These were separate trials with different participants, so the numbers aren't a direct comparison, but the pattern is consistent: tirzepatide's averages ran higher. It's worth holding these as averages, not promises. Results in any trial spread widely; some people lost far more than the mean and some far less, and every participant had structured lifestyle support alongside the drug.

When the two were tested directly against each other in the SURMOUNT-5 trial, which randomized 751 adults with obesity to one drug or the other for 72 weeks, tirzepatide came out ahead. Participants on tirzepatide lost about 20.2% of their body weight on average versus 13.7% on semaglutide, with greater waist-circumference reduction as well. That's the strongest evidence so far that, on average, tirzepatide produces more weight loss.

But "more effective on average" is not the same as "better for you." Semaglutide still produced substantial, clinically meaningful loss in the same trial, and a difference in group averages doesn't predict your individual response. Plenty of women do very well on semaglutide, and tolerability, cost, and health history can matter more in practice than a few percentage points in a study.

Both medications share a very similar side-effect profile, and it's mostly digestive: nausea, diarrhea, vomiting, constipation, and reduced appetite. These tend to be mild to moderate, show up most when the dose is increasing, and ease for many people over time. In the SURMOUNT-1 trial, nausea was the most common complaint on tirzepatide and a frequent reason people lowered their dose. Slow dose titration is the usual way prescribers manage this.

Both also carry an FDA boxed warning about a possible risk of thyroid C-cell tumors, based on animal studies. They're not prescribed to people with a personal or family history of medullary thyroid cancer or MEN 2. Rarer but serious risks like pancreatitis and gallbladder problems apply to both. This is exactly the territory where your own medical history changes the calculus, which is why the decision belongs with a prescriber, not a chart of averages.

This is often the deciding factor in real life. List prices for both run roughly $1,000, $1,350 a month, and coverage has been tightening, some pharmacy benefit managers now prefer one drug over the other, and many plans require prior authorization or won't cover weight-loss use at all. Manufacturer savings programs and self-pay vial options exist but vary, and what your specific plan covers can swing the choice entirely.

Availability has shifted too: earlier shortages have largely resolved, and regulators have moved to curb compounded versions that were sold at lower prices. Because coverage rules change often and differ by plan and employer, the practical move is to check what your insurance actually covers for each medication before you and your prescriber settle on one, sometimes the "second-best on paper" option is the one you can actually access and afford.

Here's the part the trials quietly make clear: when people stop the medication, much of the weight tends to return. In the STEP 1 extension, participants regained about two-thirds of their lost weight in the year after stopping semaglutide, and tirzepatide studies show a similar rebound after withdrawal. The medication lowers the appetite signal. It doesn't, on its own, build the eating, movement, and sleep patterns that hold a result in place.

So whichever drug you and your doctor choose, the daily habits during and after the shot are what make the difference last: enough protein to protect muscle, regular movement, decent sleep, and a steady relationship with food. The medication makes those habits easier to start because hunger is quieter, that window is the opportunity. The choice between semaglutide and tirzepatide matters, but it matters less than what you build while you're on it.