Articles / Tolerability
The side-effect toll: who stops treatment, and why it matters more than nausea
Nausea is common across every obesity drug. Dropouts for side effects range from 1% to 25%, and they do not follow nausea rates. Four patterns from the trial data.
Published Oct 23, 2026 ยท 3 min read
Almost every obesity drug causes nausea in a large share of people. That is so common across the class that it barely separates one drug from another. The figure that does separate them is the share of people who stop treatment because of side effects. Someone who quits loses the benefit, usually regains weight and has paid for nothing. Across the trials we track, that rate runs from about 1% to about 25%.
Dropouts for side effects, trial by trial
| Drug, dose, trial | Weight loss (on treatment) | Stopped for side effects | Placebo | Nausea |
|---|---|---|---|---|
| Petrelintide up to 9 mg, ZUPREME-1, 42 wk | 10.7%* | 1.0% | n/r | 20.0% |
| Tirzepatide 15 mg, SURMOUNT-1, 72 wk | 22.5% | 6.2% | 2.6% | 31.0% |
| CagriSema, REDEFINE 1, 68 wk | 22.7% | 6.0% | 3.7% | 55.0% |
| Wegovy pill 25 mg, OASIS 4, 64 wk | 16.6% | 6.9% | n/r | 46.6% |
| Semaglutide 2.4 mg, STEP 1, 68 wk | 16.9% | 7.0% | 3.1% | 44.2% |
| Orforglipron 36 mg, ATTAIN-1, 72 wk | 12.4% | 10.3% | 2.7% | 33.7% |
| MariTide, Phase 2, 52 wk | about 20%* | 11.0% | n/r | n/r |
| Retatrutide 12 mg, TRIUMPH-1, 80 wk | 28.3% | 11.3% | 4.9% | 42.4% |
| Survodutide, SYNCHRONIZE-1, 76 wk | 16.6%* | 24.5% | n/r | n/r |
* Estimand not named in the source. n/r: not reported in the sources we use. Different trials, lengths and populations; read gaps of a point or two as noise.
Four patterns in the data
1. Nausea and dropouts do not track each other. CagriSema had the highest nausea rate in the table, 55%, yet only 6.0% stopped for side effects. Orforglipron had much less nausea, 33.7%, but 10.3% stopped. That suggests dose escalation, dose reductions and how side effects are handled may matter as much as how often they happen.
2. The top dose is not always the best deal. On retatrutide, going from 9 mg to 12 mg adds 2.4 points of weight loss (25.9% to 28.3%) but raises side-effect dropouts from 6.9% to 11.3%. The 9 mg dose delivers more than 90% of the effect for about 60% of the dropouts. On tirzepatide the pattern is not even consistent: the 10 mg arm had more dropouts (7.1%) than 15 mg (6.2%).
3. Survodutide is the outlier. Survodutide, a GLP-1 and glucagon drug, stands out: about one in four participants stopped for side effects in SYNCHRONIZE-1. Retatrutide also acts on glucagon but stayed at 11.3% on its top dose, so glucagon alone does not explain the gap. For drugs that add glucagon for its promised extra benefits, higher energy use and less liver fat, tolerability is the question to watch.
4. Amylin alone is gentler, and weaker. Petrelintide, an amylin drug without GLP-1, had nausea in 20% and side-effect dropouts in about 1% over 42 weeks. Its weight loss, up to 10.7%, is also lower. That trade-off is why most amylin programmes are heading for combinations with GLP-1 drugs rather than replacing them (see our amylin explainer).
Beyond the stomach
Most side effects are gastrointestinal, but not all. Retatrutide brings a new one, dysesthesia, an unusual skin sensation reported by 12.5% on the 12 mg dose against 0.9% on placebo. In VENTURE-Oral, a short 13-week trial of the oral form of VK2735, 20% stopped for side effects against 13% on placebo. Longer Phase 3 trials will show whether slower dose increases bring that down.
What it means
As weight loss numbers converge in the low to high 20s, tolerability becomes the main way to choose between drugs. Our GLP-1 Performance Index scores each drug on weight loss per unit of side-effect burden for this reason, and the evidence map lets you plot weight loss against dropouts, nausea, vomiting, diarrhea or constipation for every trial arm.
General information, not medical advice. Sources: Eli Lilly, SURMOUNT-1; STEP 1, NEJM 2021; OASIS 4, NEJM 2025; Eli Lilly, ATTAIN-1; Eli Lilly, TRIUMPH-1; Novo Nordisk, REDEFINE 1; Fierce Biotech, SYNCHRONIZE-1; Pharmacy Times, ZUPREME-1; Viking Therapeutics, VENTURE-Oral.