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Mounjaro side effects, as its own label reports them
Mounjaro’s label reports nausea in 12, 15 and 18 of every 100 adults on 5, 10 and 15 mg, against 4 on placebo.
Source: Read from the Mounjaro label, revision 04/2026
What matters first
Medically reviewed by Jennifer Montecillo, MD · non-practicing medical reviewerReviewed 2026-08-12every number here is sourced
The two placebo-controlled diabetes trials in adults
Read the placebo column first. Nearly everything below happens to some people on a dummy injection too, and the gap between the columns is the part the drug is answerable for.
Trial armsPlacebo: n = 235Mounjaro 5 mg: n = 237Mounjaro 10 mg: n = 240Mounjaro 15 mg: n = 241
| Side effect | Placebo | Mounjaro 5 mg | Mounjaro 10 mg | Mounjaro 15 mg |
|---|---|---|---|---|
| Nausea | 4% | 12% | 15% | 18% |
| Diarrhea | 9% | 12% | 13% | 17% |
| Appetite loss | 1% | 5% | 10% | 11% |
| Vomiting | 2% | 5% | 5% | 9% |
| Constipation | 1% | 6% | 6% | 7% |
| Indigestion | 3% | 8% | 8% | 5% |
| Belly pain | 4% | 6% | 5% | 5% |
The trial in patients aged 10 and older
Trial armsPlacebo: size not publishedMounjaro 5 mg: size not publishedMounjaro 10 mg: size not published
| Side effect | Placebo | Mounjaro 5 mg | Mounjaro 10 mg |
|---|---|---|---|
| Vomiting | 3% | 16% | 12% |
| Belly pain | 9% | 22% | 15% |
The boxed warning: thyroid tumors in rodents
Like every drug in this family, Mounjaro opens with a boxed warning drawn from rat studies that found thyroid C-cell tumors. The human risk is unknown. Anyone with medullary thyroid cancer in the family, or with the inherited condition MEN 2, is ruled out by the label.
What does the label tell prescribers to watch for?
These sit above the table in the label, in the section reserved for the problems that are rare but matter most.
| Warning | What this label says about it |
|---|---|
| Pancreatitis | The warning was rewritten in December 2025 to match the rest of the GLP-1 family. |
| Low blood sugar | The clearest risk here, because most people on Mounjaro are also taking other diabetes medicines. |
| Diabetic eye disease | Fast improvement in blood sugar can make existing eye damage worse. |
| Kidney injury | Usually after fluid loss from being sick or having diarrhea. |
| Severe stomach and gut problems | Rewritten in December 2025 alongside the pancreatitis warning. |
| Gallbladder disease | Reported by 0.6 in 100 adults on Mounjaro and none on placebo. |
| Serious allergic reactions | More common in people who developed antibodies to the drug. |
| Breathing in stomach contents under anesthetic | The label warns that the stomach may not be empty. |
What have people actually reported about Mounjaro?
93,975 reports naming Mounjaro have reached the FDA’s public database. A report is not proof the drug caused anything, and there is no way to know how many people took it.
| Most reported | Reports | Share of Mounjaro reports |
|---|---|---|
| Wrong dose given | 17,026 reports | 18% of Mounjaro reports |
| Nausea | 9,613 reports | 10% of Mounjaro reports |
| Injection site pain | 9,193 reports | 9.8% of Mounjaro reports |
| Off label use | 7,824 reports | 8.3% of Mounjaro reports |
| Diarrhea | 5,925 reports | 6.3% of Mounjaro reports |
| Extra dose given | 5,116 reports | 5.4% of Mounjaro reports |
| Vomiting | 5,114 reports | 5.4% of Mounjaro reports |
| Constipation | 3,635 reports | 3.9% of Mounjaro reports |
| Injection site hemorrhage | 3,540 reports | 3.8% of Mounjaro reports |
| Injection site erythema | 3,094 reports | 3.3% of Mounjaro reports |
Mounjaro’s report pile is the largest of the four brands, and its top entry is a dosing error rather than a symptom.
Pain where the injection went in ranks third, above diarrhea and vomiting. That ordering does not appear for either semaglutide pen, and it fits a product that is frequently drawn from a vial rather than clicked out of a pen.
4Interpret the page
Young patients had a rougher time than adults
The label says side effects in patients aged 10 and older matched the adult picture with three exceptions: vomiting, belly pain and low blood sugar all came up more often.
Vomiting hit 16 in every 100 on 5 mg, against 3 on placebo. Belly pain hit 22 in every 100 on 5 mg, against 9 on placebo. Both are well above what the adult table shows at the same dose.
No severe low blood sugar was reported. That is the reassuring half of the same finding, and both halves come from one 99-patient trial, which is small.
Antibodies changed who reacted at the injection site
Some people make antibodies to tirzepatide. The label reports what happened next, split by whether they did.
Among adults who developed antibodies, 4.6 in every 100 had a reaction where they injected. Among those who did not, it was 0.7. Allergic reactions split the same way, 4.1 against 3.0.
The label does not say the antibodies caused this. It publishes the split and leaves it there, which is the correct way to handle a finding with no trial designed to test it.
Why do Mounjaro and Zepbound report different numbers for the same drug?
Both are tirzepatide. The percentages differ because the trials behind them differ, not because one product is gentler than the other.
Each label opens its table with the same warning: rates from one drug’s trials cannot be set against another’s. That holds here even though the drug substance is identical. The two sets of trials enrolled different people. They ran to different doses. And they used different cut-offs for what got printed at all.
Where to read next
Two pages carry the parts this one leaves out.
- The Mounjaro dose schedule has the step pattern these percentages are attached to.
- Side effects of tirzepatide itself covers the drug across every product built on it.
Questions readers ask
What should I avoid while taking Mounjaro?
What's safer, Ozempic or Mounjaro?
What are the worst side effects of taking Mounjaro?
What are the long-term effects of Mounjaro?
- MOUNJARO (tirzepatide) injection — DailyMed SPL, sections 5, 6.1 and 8.4retrieved 2026-08-12FDA label