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Read what the GLP-1 trials actually found, in plain English, with the numbers left in.
Every major semaglutide and tirzepatide trial in one page each: who was studied, what changed, what went wrong, and what the trial cannot tell you.
- 24
- trial digests with the numbers left in
- One page per trial, from STEP 1 to the newest triple agonists.
- -14.9%
- STEP 1, semaglutide 2.4 mg at 68 weeks, vs -2.4% placebo
- Average weight change on semaglutide 2.4 mg over 68 weeks, against -2.4% on placebo.
- -20.9%
- SURMOUNT-1, tirzepatide 15 mg at 72 weeks, vs -3.1% placebo
- Average weight change on tirzepatide 15 mg over 72 weeks, against -3.1% on placebo.
Start here
Three ways in, depending on what you need right now
- 01Trial result explorerFilter 24 GLP-1 trials by drug, indication, endpoint and duration; chart weight change by arm.
- 02How to read a GLP-1 trial: estimands, placebo-subtracted change and responder thresholdsTwo people can quote different weight numbers from the same trial, and both can be right.
- 03Browse trials24 pages, most recently updated September 4, 2026
Interactive
The calculator
Each runs in your browser, shows its formula, and prints a dated assumptions note. Nothing you type leaves the page.
Reading
Start with these
Each page opens with a plain-English summary, a figure drawn from the data, the numbers that matter, and what it means if you're considering treatment.
Methods
How to read a GLP-1 trial: estimands, placebo-subtracted change and responder thresholds
You'll get: Two people can quote different weight numbers from the same trial, and both can be right.
Five checks before quoting a trial weight number: who was counted, what placebo did, how wide the range is, what a threshold means, what was measured.
Methods
Master comparison table: 24 pivotal GLP-1 and GIP/GLP-1 trials side by side
You'll get: This page puts all 24 trials on this site in one table, with a link to each write-up.
One table for all 24 trials on this site: drug, who was studied, how many, how long, what was measured, the result, who paid, and a link to the paper.
Trials
SURMOUNT-1: tirzepatide 5, 10 and 15 mg for obesity over 72 weeks
You'll get: SURMOUNT-1 is the main trial behind Zepbound and the source of the over 20 percent figure for tirzepatide.
The main tirzepatide weight trial. 2539 adults without diabetes, 72 weeks: 15 to 21 percent weight loss across three doses versus 3 percent on placebo.
Trials
SURMOUNT-4: what happens when tirzepatide is stopped
You'll get: SURMOUNT-4 took 670 adults who had been on tirzepatide for 36 weeks and had half of them switch to placebo.
After 36 weeks on tirzepatide, 670 adults kept it or switched to placebo for 52 weeks. Kept it: lost 5.5 percent more. Switched: regained 14 percent.
Trials
SURMOUNT-5: tirzepatide against semaglutide, head to head
You'll get: SURMOUNT-5 is the first trial to test tirzepatide against semaglutide head to head in people with obesity and no diabetes.
First head-to-head in obesity without diabetes. 751 adults, highest tolerated dose of each, 72 weeks. Tirzepatide about 20 percent, semaglutide about 14.
Live updates
What changed since this site was written
Sources checked October 23, 2026, refreshed every six hours.
Newest on PubMed
Papers indexed in the last year matching randomised trials of incretin agents (102 in total).
- Glycaemic Changes After Semaglutide Discontinuation in Adults With Type 1 Diabetes Using Automated Insulin Delivery: Analysis of the ADJUST-T1D Extension Study
Diabetes Obes Metab · November 1, 2026 · PubMed 42675550
- Retatrutide-Associated Improvements in Cardiovascular Risk Biomarkers in Adults With Obesity With or Without Type 2 Diabetes
Diabetes Obes Metab · November 1, 2026 · PubMed 42608321
- Efficacy of Luseogliflozin Added to Semaglutide in Patients With Metabolic Dysfunction-Associated Steatohepatitis and Type 2 Diabetes Mellitus: A Randomised, Open-Label Trial
Diabetes Obes Metab · November 1, 2026 · PubMed 42605535
- Semaglutide modulates explore/exploit decision-making in major depressive disorder: A randomized clinical trial
Psychol Med · October 21, 2026 · PubMed 42904347
- Cardiovascular safety of orforglipron versus insulin glargine in adults with type 2 diabetes at increased cardiovascular risk (ACHIEVE-4): a phase 3, event-driven, randomised, open-label, non-inferiority, active comparator trial
Lancet · October 17, 2026 · PubMed 42815506
FDA and enforcement tracker
FormBlends research feed, data as of September 4, 2026.
September 1, 2026 · Adverse-event report update
FDA GLP-1 concerns page updated: 990 adverse-event reports for compounded semaglutide and >730 for compounded tirzepatide (as of May 31, 2026); border screening and fake-pharmacy labelsAugust 28, 2026 · Label or price event
FDA approves Mounjaro (tirzepatide) to reduce MACE risk in adults with type 2 diabetes (SURPASS-CVOT)August 27, 2026 · Court decision
Fifth Circuit affirms summary judgment for FDA in both GLP-1 shortage cases (Nos. 25-10600 tirzepatide; 25-10758 semaglutide)August 24, 2026 · FDA warning letter
FDA warning letters to five peptide vendors: Peak Performance Peptides (735127), Royal Peptides (734884), NuScience Peptides (733652), Peptide Partners (735063), TXP Innovations dba Tex Peptides (735067)August 24, 2026 · FDA warning letter
FDA warning letter: TXP Innovations LLC dba Tex Peptides (Unapproved New Drugs/Misbranded)
Compounded price index
Median all-in cash price per 28 days across providers, as of September 3, 2026.
- semaglutide, month 1 at 0.25 mg/week
- $197
- median of 14 providers
- semaglutide, month 4 at 1 mg/week
- $199
- median of 13 providers
- tirzepatide, month 1 at 2.5 mg/week
- $268
- median of 14 providers
- tirzepatide, month 4 at 5 mg/week
- $299
- median of 12 providers
- September 3, 2026: Index, All, baseline 51 rows. First weekly snapshot. Changes against this baseline will be listed here with the date they were observed.
PubMed lists come from NCBI E-utilities and are not reviewed by us before they appear. Feeds are FormBlends Research data (CC BY 4.0); FormBlends sells compounded GLP-1 drugs and appears in the price index under the same rules as every other provider. Compounded drugs are not FDA approved.
Browse
Sections
27 pages across 2 sections, each sourced to a label, a trial or a dated manufacturer page.
Trials
You'll get: 24 sourced pages, each with a plain-English opener
The main tirzepatide weight trial. 2539 adults without diabetes, 72 weeks: 15 to 21 percent weight loss...
Methods
You'll get: 3 sourced pages, each with a plain-English opener
Five checks before quoting a trial weight number: who was counted, what placebo did, how wide the range is,...
How the digests are written
Each digest starts from the PubMed abstract of the primary paper, fetched directly from the NCBI database, and where the full text is open access, from that too. We report the estimand the authors used, keep the confidence interval next to the point estimate, and separate the coprimary endpoints from the secondary ones. Numbers that appear only in press releases, conference slides or secondary reviews are left out. If a figure you expect is missing, it is because the abstract does not state it.
What a trial digest is not
A digest is not a recommendation and it is not a comparison between drugs unless the trial itself was head-to-head. Population averages from selected, monitored trial participants do not predict any one person's result, and none of these trials studied compounded products, which are not FDA approved and not interchangeable with the brand products that were tested. Talk to a prescriber about what any of this means for you.