Most stomach side effects on semaglutide and tirzepatide show up while the dose is going up, and the labels say they tend to fade after that. That is the short version of what the FDA labels for Wegovy, Ozempic, Zepbound and Mounjaro say about timing. This guide walks through each phase, the first dose, each step-up and maintenance, using only what the labels and the main trials report.
One limit up front: none of these labels publishes a week-by-week chart of who felt sick when. They give overall trial rates and a few plain statements about when most events happened. So this is not a forecast. It is what the data says about timing, and where it goes quiet.
All four labels start you on a low dose and raise it in steps of at least 4 weeks. Each label gives the same reason: the schedule is there "to reduce the risk of gastrointestinal adverse reactions." Gastrointestinal, or GI, just means the stomach and gut: nausea, vomiting, diarrhea, constipation and belly pain (Wegovy label, 2.2; Zepbound label, 2.1; Ozempic label, 2.2; Mounjaro label, 2.1).
| Drug | Start | Steps in the label | Top dose |
|---|---|---|---|
| Wegovy (semaglutide) | 0.25 mg, weeks 1–4 | 0.5 mg weeks 5–8, 1 mg weeks 9–12, 1.7 mg weeks 13–16 | 2.4 mg from week 17 (7.2 mg allowed for some adults) |
| Ozempic (semaglutide) | 0.25 mg for 4 weeks | 0.5 mg, then 1 mg and 2 mg, each after at least 4 weeks | 2 mg |
| Zepbound (tirzepatide) | 2.5 mg for 4 weeks | 5 mg, then up by 2.5 mg after at least 4 weeks on the current dose | 15 mg |
| Mounjaro (tirzepatide) | 2.5 mg | Up by 2.5 mg after at least 4 weeks on the current dose | 15 mg (adults) |
On Wegovy, that means the climb to 2.4 mg takes 16 weeks. The weight-loss trials behind the labels used similar windows: the Wegovy heart trial had a 16-week escalation period (Wegovy label, 14.1), and the SURMOUNT-1 tirzepatide trial included a 20-week dose-escalation period (Jastreboff 2022). The glossary explains titration, the term for this stepping up.
The starting dose is not meant to do the full job. The Zepbound label says it outright: 2.5 mg "is for treatment initiation and is not approved as a maintenance dosage" (Zepbound label, 2.1). Wegovy's 0.25 mg and Ozempic's 0.25 mg play the same role.
What do the labels say about the first weeks specifically? Three things:
What the labels do not give is a first-week nausea rate.
This is where the labels are clearest. Every one of them ties most GI events to the escalation period:
The pooled trial analyses say the same. Across the STEP 1 to 3 semaglutide 2.4 mg trials, most GI events were mild to moderate (98.1%), transient, and "occurred most frequently during/shortly after dose escalation" (Wharton 2022). Across SURMOUNT-1 to 4 for tirzepatide, most GI events were non-serious and occurred during dose escalation, and when people did need anti-nausea or anti-diarrhea medicine, the first use was most often during escalation (Rubino 2025).
The labels do not say how many days a flare lasts after a step-up. They only say events cluster in the climbing phase.
These are calls for your prescriber, not changes to make on your own.
The Wegovy label says that if 2 or more doses in a row are missed, the prescriber should restart escalation at a lower dose "to reduce the risk of gastrointestinal adverse reactions" (Wegovy label, 2.4). The Wegovy, Ozempic, Zepbound and Mounjaro missed-dose pages lay out each label's rule.
The clearest maintenance data comes from STEP 4. Everyone took Wegovy through a 20-week run-in that included 16 weeks of escalation. During that run-in, 11% stopped the drug, most often because of side effects (5.3%). The 803 people who reached 2.4 mg were then randomized to keep going or switch to placebo (Wegovy label, 14.2). The pooled analysis of that phase says 2.4 mg maintenance "was well tolerated" (Wharton 2022).
The Zepbound label adds a matching point about who quits. Most people who stopped Zepbound because of side effects "did so during the first few months of treatment due to gastrointestinal adverse reactions" (Zepbound label, 6.1).
Going above 2.4 mg is a new step. Wegovy now allows 7.2 mg for adults who have tolerated 2.4 mg for at least 4 weeks and need more weight loss (Wegovy label, 2.2). In those trials, nausea was 39% on 7.2 mg, 35% on 2.4 mg and 13% on placebo. Changes in skin feeling, which the label calls dysesthesia, were 22% on 7.2 mg versus 6% on 2.4 mg (Wegovy label, 6.1).
These are the label rates for the four main stomach side effects across the whole trial, not per week. The Wegovy and Zepbound numbers come from weight-loss trials. The Ozempic and Mounjaro numbers come from type 2 diabetes trials, which used lower doses and different people, so the labels warn that rates cannot be compared directly from one drug to another.
| Label, dose | Nausea | Diarrhea | Vomiting | Constipation |
|---|---|---|---|---|
| Wegovy placebo | 16% | 16% | 6% | 11% |
| Wegovy 2.4 mg | 44% | 30% | 24% | 24% |
| Zepbound placebo | 8% | 8% | 2% | 5% |
| Zepbound 5 mg | 25% | 19% | 8% | 17% |
| Zepbound 10 mg | 29% | 21% | 11% | 14% |
| Zepbound 15 mg | 28% | 23% | 13% | 11% |
| Ozempic placebo | 6.1% | 1.9% | 2.3% | 1.5% |
| Ozempic 0.5 mg | 15.8% | 8.5% | 5% | 5% |
| Ozempic 1 mg | 20.3% | 8.8% | 9.2% | 3.1% |
| Mounjaro placebo | 4% | 9% | 2% | 1% |
| Mounjaro 5 mg | 12% | 12% | 5% | 6% |
| Mounjaro 10 mg | 15% | 13% | 5% | 6% |
| Mounjaro 15 mg | 18% | 17% | 9% | 7% |
Sources: Wegovy Table 3, Zepbound Table 1, Ozempic Table 1, Mounjaro Table 1, all in section 6.1 of each label. Note that the placebo groups also report these symptoms. On Wegovy, 47% of people on placebo reported some GI reaction, against 73% on the drug (Wegovy label, 6.1).
| Label | Stopped for any side effect | Stopped for GI side effects | Severe GI reactions |
|---|---|---|---|
| Wegovy 2.4 mg vs placebo | 6.8% vs 3.2% | 4.3% vs 0.7% | 4.1% vs 0.9% |
| Zepbound 5 / 10 / 15 mg vs placebo | 4.8% / 6.3% / 6.7% vs 3.4% | 1.9% / 3.3% / 4.3% vs 0.5% | 1.7% / 2.5% / 3.1% vs 1% |
| Ozempic 0.5 / 1 mg vs placebo | not stated in the sections we used | 3.1% / 3.8% vs 0.4% | 0.4% / 0.8% vs 0% |
| Mounjaro 5 / 10 / 15 mg vs placebo | not stated in the sections we used | 3.0% / 5.4% / 6.6% vs 0.4% | 1.3% / 0.4% / 1.2% vs 0.9% |
Sources: section 6.1 and the severe GI warning in each label (Wegovy label, 5.6; Zepbound label, 5.2; Ozempic label, 5.7; Mounjaro label, 5.6). The single most common reason people left Wegovy was nausea, at 1.8% versus 0.2% on placebo (Wegovy label, 6.1). In the trials themselves, STEP 1 reported 4.5% stopping for GI events versus 0.8% on placebo (Wilding 2021), and SURMOUNT-1 reported 4.3%, 7.1% and 6.2% stopping for any side effect on 5, 10 and 15 mg versus 2.6% on placebo (Jastreboff 2022).
The Medication Guides, the plain-language part of each label written for patients, list these signals (Wegovy Medication Guide; Zepbound Medication Guide):
The guides also say to tell every provider about the drug before surgery or sedation.
Because the labels only say "mostly during escalation," your own pattern is worth writing down. Dose Track lets you log each dose across all your compounds, set reminders, keep track of pens and vials, and log side effects on the day they happen, so you and your prescriber can see whether symptoms bunch up after each step-up and settle after. The guide to tracking GLP-1 doses and side effects covers what to log, and the GLP-1 tracking guide shows how the app handles it. For nausea specifically, see GLP-1 nausea: what the labels say.
This article is general information, not medical advice. Talk to your prescriber before you start, change or stop any medicine.