GLP-1 side effect rates, and why they cannot be compared
All four labels report nausea, vomiting, diarrhea and constipation. They report them in different populations, against different comparators, at different reporting thresholds and over different trial lengths — and every one of them prints a sentence saying the numbers must not be compared across drugs. The tables below are therefore reproduced separately, each with the conditions that produced it.
Ellis Brandt built this site’s grading methodology and maintains it. Rates read from section 6.1 of each label's own tables. Last re-read September 2026.
Not medical advice. Semaglutide and tirzepatide are prescription-only medicines, and whether one is appropriate for you is a question for a licensed clinician who knows your history. This page reports what the FDA-approved prescribing information says and nothing else; it is not written or reviewed by a clinician. See the medical disclaimer.
Why these four tables are not one table
A reader who wants to know whether semaglutide or tirzepatide causes more nausea is asking a reasonable question that these documents do not answer. The two diabetes labels report rates in patients with type 2 diabetes at a threshold of 5%; the two weight labels report rates in patients with obesity or overweight at a threshold of 2% and greater than placebo. A 44% in one table and an 18% in another describe different people, different doses and different counting rules.
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| Label | Population in the table | Reporting threshold | Comparator arm |
|---|---|---|---|
| Ozempic | Adults with type 2 diabetes mellitus, placebo-controlled trials | Reported in at least 5% of Ozempic-treated patients | Placebo, N=262 |
| Wegovy | Adults with obesity or overweight, for weight reduction | At least 2% and greater than placebo | Placebo, N=1,261 |
| Mounjaro | Adults with type 2 diabetes mellitus, pool of placebo-controlled trials | Reported in at least 5% of Mounjaro-treated patients | Placebo, N=235 |
| Zepbound | Adults with obesity or overweight, weight reduction and long-term maintenance trials (Study 1 and Study 2) | At least 2% and greater than placebo | Placebo, N=958 |
Ozempic
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| Adverse reaction | Placebo (N=262) % | Ozempic 0.5 mg (N=260) % | Ozempic 1 mg (N=261) % |
|---|---|---|---|
| Nausea | 6.1 | 15.8 | 20.3 |
| Vomiting | 2.3 | 5 | 9.2 |
| Diarrhea | 1.9 | 8.5 | 8.8 |
| Abdominal pain | 4.6 | 7.3 | 5.7 |
| Constipation | 1.5 | 5 | 3.1 |
The same section reports gastrointestinal adverse reactions overall at placebo 15.3%, Ozempic 0.5 mg 32.7% and Ozempic 1 mg 36.4%, and states that “the majority of reports of nausea, vomiting, and/or diarrhea occurred during dose escalation.” Discontinuation because of a gastrointestinal reaction: 0.4% on placebo, 3.1% on 0.5 mg, 3.8% on 1 mg.
Percent of patients in each arm of the label's pooled placebo-controlled trials. The track is 100% of the arm, so the unfilled part of each bar is the share who reported none.
Ozempic prescribing information, section 6.1, “Gastrointestinal Adverse Reactions”, in the pool of placebo-controlled trials. Label version 20, effective 2026-06-01, read September 2026. These are one label’s numbers and are not comparable to any other label’s — that is what the sentence at the top of this page says, and it is why this figure draws three arms of one trial rather than four drugs.
Wegovy
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| Adverse reaction | Placebo (N=1,261) % | Wegovy injection 2.4 mg once weekly (N=2,116) % |
|---|---|---|
| Nausea | 16 | 44 |
| Diarrhea | 16 | 30 |
| Vomiting | 6 | 24 |
| Constipation | 11 | 24 |
| Abdominal pain | 10 | 20 |
| Headache | 10 | 14 |
| Fatigue | 5 | 11 |
| Dyspepsia | 3 | 9 |
| Dizziness | 4 | 8 |
| Hair loss | 1 | 3 |
Ten rows of a longer table, chosen as the ones a reader asks about; the label’s own table runs to nineteen. In these trials 6.8% of patients on Wegovy 2.4 mg and 3.2% on placebo permanently discontinued because of an adverse reaction — most often nausea (1.8% against 0.2%), vomiting (1.2% against 0%) and diarrhea (0.7% against 0.1%).
The label carries a second table for the 7.2 mg dosage, against both placebo and 2.4 mg. There, nausea is 13% on placebo, 35% on 2.4 mg and 39% on 7.2 mg, and dysesthesia — an abnormal sensation — is 0%, 6% and 22%.
Mounjaro
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| Adverse reaction | Placebo (N=235) % | 5 mg (N=237) % | 10 mg (N=240) % | 15 mg (N=241) % |
|---|---|---|---|---|
| Nausea | 4 | 12 | 15 | 18 |
| Diarrhea | 9 | 12 | 13 | 17 |
| Decreased appetite | 1 | 5 | 10 | 11 |
| Vomiting | 2 | 5 | 5 | 9 |
| Constipation | 1 | 6 | 6 | 7 |
| Dyspepsia | 3 | 8 | 8 | 5 |
| Abdominal pain | 4 | 6 | 5 | 5 |
Zepbound
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| Adverse reaction | Placebo (N=958) % | 5 mg (N=630) % | 10 mg (N=948) % | 15 mg (N=941) % |
|---|---|---|---|---|
| Nausea | 8 | 25 | 29 | 28 |
| Diarrhea | 8 | 19 | 21 | 23 |
| Vomiting | 2 | 8 | 11 | 13 |
| Constipation | 5 | 17 | 14 | 11 |
| Abdominal pain | 5 | 9 | 9 | 10 |
| Dyspepsia | 4 | 9 | 9 | 10 |
| Injection site reactions | 2 | 6 | 8 | 8 |
| Hair loss | 1 | 5 | 4 | 5 |
Eight rows of a sixteen-row table. The Zepbound label also quantifies the severe end: in a pool of two weight-reduction trials, severe gastrointestinal adverse reactions were reported in 1% on placebo, 1.7% on 5 mg, 2.5% on 10 mg and 3.1% on 15 mg. The same section states that Zepbound “is not recommended in patients with severe gastroparesis.”
What none of these tables tells you
They are trial rates, and every label says so itself, once, in the sentence quoted at the top of this page — the phrase “may not reflect the rates observed in practice” is the tail of that same sentence, not a second warning. Counted in each document: it occurs exactly once on each of the four. They describe selected populations followed for a fixed period under supervision, and they are the best-quality numbers that exist for these products. They are not a forecast for any individual, and this site does not turn them into one.
They also say nothing about compounded semaglutide or compounded tirzepatide, which have no approved label and no trial tables of their own. Related: the dose escalation schedules, which is where each label locates most of these reactions.
Sources
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| Label | Applicant on the label | SPL version | Label effective date | Where it was read |
|---|---|---|---|---|
| Ozempic (semaglutide) | Novo Nordisk Pharmaceutical Industries, LP | 20 | 2026-06-01 | DailyMed, set id adec4fd2-6858-4c99-91d4-531f5f2a2d79 |
| Wegovy (semaglutide) | Novo Nordisk Pharmaceutical Industries, LP | 19 | 2026-06-18 | DailyMed, set id ee06186f-2aa3-4990-a760-757579d8f77b |
| Mounjaro (tirzepatide) | Eli Lilly and Company | 40 | 2026-08-27 | DailyMed, set id d2d7da5d-ad07-4228-955f-cf7e355c8cc0 |
| Zepbound (tirzepatide) | Eli Lilly and Company | 40 | 2026-08-28 | DailyMed, set id 487cd7e7-434c-4925-99fa-aa80b1cc776b |
Every percentage on this page was read out of the structured table in the source document, not out of its running text. Each capture was checked against its own document title before anything was quoted from it, and a nonsense set id was fetched through the identical method in the same session as a control — it returned 404 with an empty body, so a document that returns is a document that exists.
See the providers
Side effects are a property of the drug, not the seller. The boards list who sells it and what each one publishes.
- Semaglutide providersprovider board
Readers who have settled on semaglutide and are choosing who to buy it from.
- Tirzepatide providersprovider board
Readers who have settled on tirzepatide and are choosing who to buy it from.
More, read from the same labels
- Semaglutide vs tirzepatidereading the label
What the four FDA-approved labels say each molecule is, what each is approved to treat, and where the two differ.
- Dose escalation schedulesreading the label
The starting dose, the escalation interval and the maximum dose each label sets, and why they are not interchangeable.
- Missed dose rulesreading the label
The window each label gives for a late dose, and the minimum gap it requires when the injection day changes.
- Drug interactionsreading the label
Insulin and sulfonylureas, oral medications, and the oral-contraceptive precaution that appears on two of these four labels and not the other two.
- Buying one onlinereading the label
The agency's own warning signs for a telehealth GLP-1 seller, its 28-day vial rule, and what it says about drugs that arrive warm.
- Who should not take onereading the label
The boxed warning every one of these labels carries, the two contraindications, and which warnings appear on which product.
The sentence on every label
“Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.”
Printed at the head of section 6.1 on Ozempic, Mounjaro and Zepbound, read September 2026. Wegovy prints the same sentence with one word changed — “…cannot be directly compared to rates in the clinical studies of another drug”.