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Tirzepatide success rate: what the trials actually show

By the Tirz Rx Editorial Team · 18 min read

Last updated 2026-07-30

TL;DR

In SURMOUNT-1, 91% of people on the highest tirzepatide dose lost at least 5% of body weight, with average loss of 20.9% at 72 weeks. For diabetes (SURPASS trials), A1C dropped 1.8 to 2.1 points on average. Success depends heavily on dose, duration, and whether you stay on treatment.

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Researchers running the SURMOUNT and SURPASS trials didn't use a single pass/fail bar. They tracked several thresholds at once: the percentage of people who lost at least 5% of body weight, at least 10%, at least 15%, at least 20%, and the average (mean) percent weight loss across the whole group. For diabetes trials, success meant A1C reduction and the share of patients who reached A1C under 7% (or under 5.7%, which is normal range). This matters because "success rate" isn't one number. A drug can have a 91% response rate at the 5% threshold and a much lower rate at the 20% threshold. When you see a headline stat, check which bar it's clearing. The FDA approved tirzepatide under two brand names for two different jobs: Mounjaro for type 2 diabetes (approved May 2022) and Zepbound for chronic weight management (approved November 2023) [1][2]. Both are the same molecule, dosed the same way, just labeled for different indications and studied in different trial families.

What percentage of people lose weight on tirzepatide?

Lost ≥5% body weight85%89%91%35%
Lost ≥10% body weight69%79%84%15%
Lost ≥20% body weight36%50%57%3%
Mean weight loss15.0%19.5%20.9%3.1%These numbers come from SURMOUNT-1 (NCT04184622), a 72-week, double-blind, placebo-controlled trial in adults with obesity or overweight (without diabetes) [3]. The study, published in the New England Journal of Medicine, concluded that "tirzepatide, at all three doses, reduced body weight and improved cardiometabolic measures in participants with obesity or overweight" [3]. A meaningful chunk of people, 57% on the top dose, crossed the 20% weight loss line. For context, that's in the range historically seen with bariatric surgery for some procedures, though surgery and drug trials aren't directly comparable in study design or follow-up length. For readers who want to see what these percentages look like in practice, the tirzepatide before and after breakdown pairs these numbers with realistic timelines by month.

In SURMOUNT-1, the trial supporting Zepbound's approval, 91% of participants on the 15 mg dose lost at least 5% of body weight at 72 weeks, compared to 35% on placebo [3]. That's the most commonly cited "success rate" figure, and it holds up across independent summaries of the trial. Breaking it down further by dose, using the trial's reported thresholds: | Outcome | 5 mg | 10 mg | 15 mg | Placebo |

How does tirzepatide's success rate compare for people with type 2 diabetes?

The SURPASS trial program, five main studies (SURPASS-1 through SURPASS-5), tested tirzepatide specifically in people with type 2 diabetes, mostly measuring blood sugar control rather than weight loss as the primary endpoint. In SURPASS-2 (NCT03987919), which compared tirzepatide head-to-head against semaglutide 1 mg, tirzepatide at the 10 mg and 15 mg doses reduced A1C by 2.01% and 2.30% respectively, versus 1.86% for semaglutide, over 40 weeks [4]. The trial's published conclusion stated that "tirzepatide was noninferior, and superior, to semaglutide with respect to the mean change in the glycated hemoglobin level" [4]. Across the SURPASS program generally, a large share of participants, often 80-90% depending on dose and baseline A1C, reached an A1C under 7%, which is the standard treatment target used by the American Diabetes Association [5]. Weight loss in these diabetes trials was real but smaller than in the obesity-specific SURMOUNT trials, typically in the 7-13% range depending on dose, likely because people with longstanding type 2 diabetes often have more insulin resistance and different baseline metabolic conditions. If you're weighing whether the diabetes benefit or the weight benefit matters more for your situation, is tirzepatide worth it walks through both angles side by side.

SURMOUNT-1: share of participants reaching each weight-loss threshold at 72 weeks By tirzepatide dose vs. placebo 35% Placebo, ≥5% lo… 85% 5 mg, ≥5% loss 89% 10 mg, ≥5% loss 91% 15 mg, ≥5% loss 84% 15 mg, ≥10% loss 57% 15 mg, ≥20% loss Source: New England Journal of Medicine, SURMOUNT-1 (2022)

Does the success rate hold up over the long term?

The 72-week data gets most of the attention, but a few things happen if you extend the timeline or stop treatment. SURMOUNT-4 (NCT04660643) specifically tested what happens when people stop tirzepatide after losing weight. Participants took tirzepatide for 36 weeks, then were randomized to either continue the drug or switch to placebo for another 52 weeks. Those who continued kept losing weight, ending around 25.3% total loss. Those switched to placebo regained a significant portion, ending around 9.9% total loss from baseline, meaning they'd given back roughly two-thirds of what they'd lost [6]. That's the single most important fact about "success rate" that trial press releases tend to bury: tirzepatide's results are conditional on staying on it. This isn't unique to tirzepatide. It's consistent with how GLP-1/GIP drugs work mechanically. They suppress appetite and slow gastric emptying while active; stop the drug and the underlying hunger signaling tends to return. For a month-by-month sense of how the curve actually looks in the first stretch of treatment, see tirzepatide first month what to expect and the fuller tirzepatide results timeline.

Does dose affect how likely tirzepatide is to work?

Yes, clearly. Every trial shows a dose-response relationship: the 15 mg (or maximum studied) dose consistently outperforms 10 mg, which outperforms 5 mg, both for weight loss percentage and for the share of people crossing each response threshold. This is exactly why prescribers titrate slowly, usually starting at 2.5 mg for four weeks, then stepping up every four weeks toward a maintenance dose of 5, 10, or 15 mg. The titration schedule exists mainly to manage GI side effects, not because lower doses don't work at all. Some people do well and stay on 5 or 7.5 mg long-term if they're hitting their goals with fewer side effects. The FDA label for Zepbound lists maintenance doses of 5 mg, 10 mg, and 15 mg once weekly, with a starting dose of 2.5 mg for the first four weeks used to reduce gastrointestinal side effects rather than for therapeutic effect [7].

Who is least likely to succeed on tirzepatide?

Trial data and clinical experience point to a few patterns worth naming honestly. People who can't tolerate the GI side effects long enough to reach a therapeutic dose sometimes stop before they'd see meaningful results. In SURMOUNT-1, gastrointestinal events (nausea, diarrhea, constipation, vomiting) were the most common adverse events and the leading cause of treatment discontinuation, occurring in a minority but meaningful share of participants, generally mild to moderate and clustering around dose increases [3]. People who don't pair the drug with any change in eating pattern sometimes see smaller results than trial participants, because SURMOUNT and SURPASS trials included counseling on a reduced-calorie diet and increased physical activity as part of the protocol, not tirzepatide alone [3][4]. People who stop the drug once they hit a goal weight, as SURMOUNT-4 showed, tend to regain a substantial share of the loss within about a year [6]. And there's a subset of "non-responders" in every GLP-1/GIP trial, roughly 9-15% of people even at the highest doses who don't reach even the 5% weight loss threshold. The biology behind who responds less isn't fully mapped yet; it's an honest gap in the research.

How does tirzepatide's success rate compare to semaglutide?

The most direct comparison comes from SURMOUNT-1 versus the semaglutide obesity trial STEP 1, and more rigorously from SURPASS-2, which put tirzepatide and semaglutide in the same trial against each other for diabetes. In SURPASS-2, tirzepatide beat semaglutide 1 mg on A1C reduction (2.30% vs 1.86% at the 15 mg dose) and on weight loss (11.2 kg vs 5.7 kg average) over 40 weeks [4]. This was a real head-to-head, randomized trial, which makes it more reliable than cross-trial comparisons of separate studies with different populations and protocols. For weight-specific outcomes, semaglutide's STEP 1 trial (using Wegovy, 2.4 mg weekly) showed an average of 14.9% weight loss at 68 weeks, versus tirzepatide's 20.9% at the 15 mg dose over 72 weeks in SURMOUNT-1. These are different trials in different populations run at different times, so the comparison is suggestive, not definitive. But no head-to-head weight-loss trial has reversed that general pattern so far. A full side-by-side on mechanism, side effects, and cost lives at tirzepatide pros and cons if you're deciding between the two drug classes.

What does "success" look like beyond the scale?

Weight loss percentage is the headline number, but SURMOUNT and SURPASS trials tracked several other outcomes that matter for real-world success. In SURMOUNT-1, participants on tirzepatide saw improvements in waist circumference, blood pressure, and lipid markers alongside weight loss [3]. SURMOUNT-2, which specifically enrolled people with type 2 diabetes and obesity, showed similar metabolic improvements in a population that typically responds less dramatically to weight-loss interventions generally. There's also a cardiovascular angle developing. The SURMOUNT-MMO and SURPASS-CVOT trials are ongoing or recently reported, aimed at nailing down tirzepatide's effect on heart attack, stroke, and cardiovascular death, similar to what's already been established for some GLP-1 drugs. As of this writing, tirzepatide doesn't yet have the same length of cardiovascular outcomes evidence as older GLP-1 drugs like semaglutide (which has the SELECT trial behind it), so anyone weighing heart-health benefits specifically should treat that as an evolving area, not a settled one.

What side effects affect whether people can stay on tirzepatide long enough to succeed?

Because tirzepatide's benefits depend on staying on the drug, side effects that cause people to quit early are functionally part of the success-rate story, not a separate topic. The most common side effects across SURMOUNT and SURPASS trials are gastrointestinal: nausea, diarrhea, decreased appetite, vomiting, and constipation. These are usually worse during dose increases and tend to ease over several weeks at a stable dose [3][4]. More serious but less common risks include acute pancreatitis, gallbladder problems (including gallstones), severe gastrointestinal disease, and hypoglycemia when combined with insulin or sulfonylureas [7]. People with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2) should not take tirzepatide at all. This is a boxed warning on the FDA label, the agency's most serious category of warning, based on thyroid C-cell tumors observed in rodent studies; it's not yet confirmed whether this risk translates to humans, but the precaution stands regardless [7]. Anyone reading trial success rates should weigh them against this real safety profile, more than the percentages on the scale. None of the numbers above make sense in isolation from the tolerability question.

Is compounded tirzepatide's success rate the same as the branded drug's?

Short answer: nobody actually knows, and that's worth saying plainly. All the percentages above (91%, 20.9%, 2.3% A1C reduction) come from trials of FDA-approved Mounjaro and Zepbound, manufactured by Eli Lilly under controlled, tested conditions. Compounded tirzepatide, made by compounding pharmacies during the FDA-declared shortage period, was never itself run through a randomized controlled trial measuring these outcomes. The active molecule, when compounded correctly by a legitimate, licensed pharmacy, should behave the same way pharmacologically, tirzepatide is tirzepatide. But compounding introduces variables the trials didn't test: differences in salt form, vehicle, sterility practices, and dosing accuracy from pharmacy to pharmacy. The FDA has published warnings about tirzepatide products sold online, including versions found to be counterfeit or containing incorrect ingredients [8]. As of the FDA's updates on the tirzepatide shortage, the agency removed tirzepatide from its shortage list in late 2024, which narrows the legal basis for mass compounding under section 503A and 503B going forward, though compounding for individual patients with documented clinical need can still occur [9]. If you're considering a compounded route, the safety of your outcome depends heavily on the pharmacy's licensing and testing practices, more than the molecule. This is where working with a provider-reviewed pathway matters. Tirz Rx reviews providers and points readers toward routes that use licensed, verified fulfilling pharmacy partners rather than unregulated sellers, precisely because the success-rate data above only applies cleanly to product that matches what was actually studied.

What should you actually expect, realistically?

If you're starting tirzepatide for weight loss, the honest expectation based on SURMOUNT-1 is: most people (around 9 in 10 on the top dose) will lose at least 5% of body weight, a majority will cross 10%, and a bit over half will cross 20%, if they stay on treatment for the better part of a year and a half and tolerate the drug well [3]. If you're starting it for type 2 diabetes, expect A1C reduction in the 1.8 to 2.3 percentage point range on average, with a strong chance (most participants in SURPASS trials) of reaching under 7% [4][5]. What the averages hide: individual results vary a lot, some people lose far more, some far less, some barely respond, and stopping the drug tends to reverse a large share of the benefit within a year [6]. Read the tirzepatide reviews roundup for how these trial numbers line up (or don't) with what real patients report, and check tirzepatide before and after for visual and timeline context before you start.

Frequently asked questions

What percentage of people lose weight on tirzepatide?

In SURMOUNT-1, 91% of participants on the 15 mg dose lost at least 5% of body weight at 72 weeks, compared to 35% on placebo. Average weight loss was 20.9% on the top dose. Lower doses (5 mg, 10 mg) showed slightly lower response rates but still well above placebo across every threshold measured.

Does tirzepatide work for everyone?

No. Roughly 9-15% of participants even at the highest studied dose didn't reach the 5% weight loss threshold in SURMOUNT-1. Response varies by individual biology, adherence to dosing, diet and activity changes made alongside the drug, and how well someone tolerates the GI side effects long enough to reach a therapeutic dose.

How long does it take to see results on tirzepatide?

Trial data shows measurable weight loss beginning within the first 4-8 weeks, with the steepest average loss occurring during dose escalation over the first several months. SURMOUNT-1 measured its primary results at 72 weeks, so meaningful comparisons to trial percentages require staying on treatment for well over a year.

What happens if you stop tirzepatide after reaching your goal?

SURMOUNT-4 found that participants who switched to placebo after 36 weeks of tirzepatide regained a large share of lost weight, ending around 9.9% total loss versus 25.3% for those who continued the drug, over the following 52 weeks. Most experts treat this as evidence tirzepatide needs long-term use to maintain results.

Is tirzepatide more effective than semaglutide?

In the SURPASS-2 head-to-head trial, tirzepatide produced greater A1C reduction (2.30% vs 1.86%) and more weight loss (11.2 kg vs 5.7 kg) than semaglutide 1 mg over 40 weeks in people with type 2 diabetes. Cross-trial comparisons for weight-loss-only populations also favor tirzepatide, though fewer head-to-head weight trials exist.

Does the success rate differ between Mounjaro and Zepbound?

They're the same molecule at the same doses, so the underlying pharmacology is identical. Mounjaro was studied and approved for type 2 diabetes (SURPASS trials); Zepbound was studied and approved for chronic weight management (SURMOUNT trials). The differing 'success rates' reflect different trial populations and endpoints, not a different drug.

Is compounded tirzepatide as effective as the branded version?

There's no randomized trial data on compounded tirzepatide specifically. It should work the same pharmacologically if compounded correctly, but the FDA has flagged counterfeit and mislabeled tirzepatide products sold online. Sourcing from a licensed, verified pharmacy matters more than usual because compounded product hasn't been through the same trial pipeline.

What's considered a 'good' amount of weight loss on tirzepatide?

Clinically, losing 5% or more of body weight is considered a meaningful response, since it's linked to measurable improvements in blood pressure, cholesterol, and blood sugar. Trial data shows most people on higher doses exceed that easily, with over half crossing 20% loss on the 15 mg dose in SURMOUNT-1.

Does tirzepatide help with A1C even if you don't lose much weight?

Yes. The SURPASS trials measured A1C reduction as the primary endpoint separately from weight loss, and improvements in blood sugar control were seen across dose groups even among participants with smaller weight changes, since tirzepatide's GLP-1/GIP action affects insulin secretion and glucagon suppression independent of weight loss.

Why do some people not respond to tirzepatide?

The biology of non-response isn't fully understood. Contributing factors likely include individual differences in GLP-1/GIP receptor sensitivity, inability to tolerate dose increases due to GI side effects, not reaching a therapeutic dose, and lack of accompanying diet or activity changes that trial protocols included alongside the drug.

How does dose affect tirzepatide's success rate?

Higher doses consistently produce better results. In SURMOUNT-1, average weight loss was 15.0% at 5 mg, 19.5% at 10 mg, and 20.9% at 15 mg. The percentage of people reaching 20%+ weight loss rose from 36% to 57% across that same dose range, showing a clear dose-response relationship.

Are there long-term studies on tirzepatide beyond 72 weeks?

SURMOUNT-4 followed participants through 88 weeks total. Longer-term cardiovascular outcome trials (SURPASS-CVOT and SURMOUNT-MMO) are ongoing or newly reported as of this writing. Compared to older drugs like semaglutide, which has the multi-year SELECT cardiovascular trial completed, tirzepatide's very long-term outcomes data is still developing.

Sources

  1. FDA, Mounjaro approval: Mounjaro (tirzepatide) was approved by the FDA for type 2 diabetes in May 2022
  2. FDA, Zepbound approval announcement: Zepbound (tirzepatide) was approved by the FDA for chronic weight management in November 2023
  3. New England Journal of Medicine, SURMOUNT-1 trial: SURMOUNT-1 weight loss and response-rate data by dose at 72 weeks
  4. New England Journal of Medicine, SURPASS-2 trial: SURPASS-2 head-to-head comparison of tirzepatide and semaglutide on A1C and weight
  5. American Diabetes Association, Standards of Care: A1C under 7% is the standard glycemic treatment target for most adults with type 2 diabetes
  6. JAMA, SURMOUNT-4 trial: Participants who stopped tirzepatide after 36 weeks regained weight compared to those who continued treatment
  7. FDA, Zepbound prescribing information: Zepbound dosing schedule, boxed warning on medullary thyroid carcinoma, and common adverse events
  8. FDA, counterfeit and compounded tirzepatide warning: FDA has warned about counterfeit and mislabeled GLP-1/GIP products including tirzepatide sold online
  9. FDA, drug shortage database entry for tirzepatide: FDA resolved the tirzepatide shortage in late 2024, affecting the legal basis for compounding under sections 503A/503B