Mounjaro and Zepbound are both made with tirzepatide. They are the same medicine with two FDA labels for different uses. Mounjaro is for type 2 diabetes in adults and in children aged 10 and older. It is also approved to lower the risk of heart attack, stroke, and heart-related death in some adults with type 2 diabetes. Zepbound is for weight loss in adults with obesity, or with overweight and a health problem linked to weight. It is also approved for moderate to severe sleep apnea in adults with obesity.
Each label lists the side effects seen in its own placebo-controlled trials. The tables below copy those numbers. Placebo means a shot with no medicine in it. A problem in a table is not proof that the medicine caused it.
The two tables come from separate trials. The Mounjaro trials enrolled adults with type 2 diabetes for 40 weeks. The Zepbound trials enrolled adults with obesity or overweight for up to 72 weeks. One of those two trials included only people with type 2 diabetes. Different people and different trial lengths can change how often a problem is reported. So the gap between the two tables is not a test of one label against the other.
The boxed warning on both labels
Mounjaro and Zepbound (tirzepatide): Both labels have a boxed warning, FDA's strongest kind. Tirzepatide caused thyroid C-cell tumors in rats. It is not known whether it causes them in people, including medullary thyroid cancer (MTC). People with a personal or family history of MTC, or with a condition called MEN 2, must not use it. The labels list signs of a thyroid tumor to watch for: a lump in the neck, trouble swallowing, shortness of breath, or hoarseness that does not go away.
Stomach and bowel problems, and stopping the medicine
- Mounjaro label: in the diabetes trials, 37.1% to 43.6% of adults on Mounjaro and 20.4% on placebo had a stomach or bowel problem. 3.0% to 6.6% stopped Mounjaro because of these problems, compared with 0.4% on placebo.
- Zepbound label: in the weight trials, 56% of adults on Zepbound and 30% on placebo had a stomach or bowel problem. 1.9% to 4.3% stopped Zepbound because of these problems, compared with 0.5% on placebo.
- Both labels say most nausea, vomiting, and diarrhea happened while the dose was being raised and became less common over time.
Compare each number with its own placebo number, not with the other label.
Mounjaro vs Zepbound: side effect tables
The Mounjaro table is its label's full list of problems in at least 5% of people on Mounjaro that were more common than on placebo. The Zepbound label lists problems in at least 2% of adults on Zepbound that were more common than on placebo. Its table here shows the 12 the label names as most common. In both tables, the middle column shows the lowest and highest share across three dose groups.
A problem missing from one table may still have happened. In the Mounjaro diabetes trials, allergic reactions were reported by 3.2% on Mounjaro and 1.7% on placebo, and shot-site reactions by 3.2% and 0.4%. Both are below the 5% cut for its table.
The Zepbound label also lists dizziness, gas, bloated belly, and low blood pressure, each more common than on placebo. They are in the less common table on the tirzepatide side effects page.
Low blood sugar is left out of both tables. When Mounjaro was taken alone, no one in the Mounjaro groups had a blood sugar below 54 mg/dL. On placebo, 1% did. When Mounjaro was added to long-acting insulin, 14% to 19% did, compared with 13% on placebo. In the Zepbound trial of adults with type 2 diabetes, 4.2% on Zepbound and 1.3% on placebo did.
Both labels report more low blood sugar with a diabetes medicine called a sulfonylurea. In that Zepbound trial, it happened to 10.3% of people on Zepbound who also took a sulfonylurea and 2.1% of those who did not. The Zepbound label says it can cause low blood sugar, including in adults without type 2 diabetes.
Compare each Mounjaro or Zepbound number with its own placebo number.
Mounjaro label
Mounjaro trials in adults with type 2 diabetes 40 weeks
Adults with type 2 diabetes in 2 trials. One tested Mounjaro alone. The other added it to long-acting insulin, with or without metformin. 718 adults took Mounjaro in three dose groups and 235 took placebo.
| Reported problem | Mounjaro groups | Placebo |
|---|---|---|
| Nausea | 12% to 18% | 4% |
| Diarrhea | 12% to 17% | 9% |
| Less appetite | 5% to 11% | 1% |
| Vomiting | 5% to 9% | 2% |
| Constipation | 6% to 7% | 1% |
| Indigestion (dyspepsia) | 5% to 8% | 3% |
| Belly pain | 5% to 6% | 4% |
Source for Mounjaro trials in adults with type 2 diabetes: Mounjaro prescribing information on DailyMed , label revised .
Zepbound label
Zepbound trials in adults with obesity or overweight Up to 72 weeks
Adults with obesity or overweight in 2 trials. One trial included only people with type 2 diabetes; the other left them out. 2,519 got Zepbound in three dose groups and 958 got placebo.
| Reported problem | Zepbound groups | Placebo |
|---|---|---|
| Nausea | 25% to 29% | 8% |
| Diarrhea | 19% to 23% | 8% |
| Constipation | 11% to 17% | 5% |
| Vomiting | 8% to 13% | 2% |
| Belly pain | 9% to 10% | 5% |
| Indigestion (dyspepsia) | 9% to 10% | 4% |
| Shot-site reactions, like redness, itching, or bruising | 6% to 8% | 2% |
| Tiredness or weakness (fatigue) | 5% to 7% | 3% |
| Allergic reactions, mostly rash or itching | 5% | 3% |
| Burping | 4% to 5% | 1% |
| Hair loss | 4% to 5% | 1% |
| Acid reflux (GERD) | 4% to 5% | 2% |
Source for Zepbound trials in adults with obesity or overweight: Zepbound prescribing information on DailyMed , label revised .
What these numbers do not show
- These tables come from separate trials with different people, so they cannot be compared directly.
- Each label lists more warnings than these tables show. The full tables, notes, and warnings are linked below.
- People who have had a serious allergic reaction to tirzepatide or another ingredient in the product must not use it.
- Both labels list problems reported after approval, such as pancreatitis that can be deadly, blocked bowels, severe constipation, kidney failure, and severe allergic reactions. How often these happen is not known.
- These medicines slow how fast the stomach empties. There are rare reports of people with GLP-1 medicines breathing stomach contents into the lungs during surgery or deep sedation. The labels say to tell the care team before any planned surgery or procedure.
- The labels say these medicines may make birth control pills work less well, mostly in the first weeks and after a dose increase. They advise switching to a non-pill method or adding a barrier method, such as condoms, for 4 weeks after starting and for 4 weeks after each dose increase.
- The Zepbound label does not recommend using it with other tirzepatide products or with any GLP-1 medicine.
- Each label covers its own uses. Ask the prescriber before changing, stopping, or combining any of these medicines or other diabetes medicines.
- Trials can miss rare harms and harms that take years to appear.
- These numbers describe Mounjaro and Zepbound. They do not describe compounded tirzepatide or products sold online as research tirzepatide.
Full tables, notes, and warnings
Report a side effect
You can report a suspected side effect to the FDA at 1-800-FDA-1088 or through FDA MedWatch . If a reaction feels serious, get medical care first.
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- Saxenda vs Zepbound: side effects in the weight-management labels
- Victoza vs Ozempic: side effects in the type 2 diabetes labels
- Saxenda vs Wegovy: side effects in the weight-management labels
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