Mounjaro Side Effects: What to Expect
Adverse reactions reported for tirzepatide in its pivotal trial program, plus the boxed warning and serious warnings from the FDA label.
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Most Common Mounjaro Side Effects
Adverse reactions reported in the Mounjaro FDA label, with the incidence among tirzepatide-treated patients and placebo for comparison. Figures are transcribed from the label's adverse-reactions section (DailyMed SetID d2d7da5d-ad07-4228-955f-cf7e355c8cc0).
| Adverse reaction | Incidence (Mounjaro vs placebo) |
|---|---|
| Nausea | 12–18% (placebo 4%) |
| Diarrhea | 12–17% (placebo 9%) |
| Decreased appetite | 5–11% (placebo 1%) |
| Vomiting | 5–9% (placebo 2%) |
| Constipation | 6–7% (placebo 1%) |
| Dyspepsia | 5–8% (placebo 3%) |
| Abdominal pain | 5–6% (placebo 4%) |
Source: Mounjaro FDA prescribing information via DailyMed (SetID d2d7da5d-ad07-4228-955f-cf7e355c8cc0), Section 6 Adverse Reactions. Last verified 2026-05-31. This is summary information — read the full label and talk to a prescriber.
Boxed Warning — Thyroid C-Cell Tumors
“Tirzepatide causes thyroid C-cell tumors in rats. It is unknown whether MOUNJARO causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans, as the human relevance of tirzepatide-induced rodent thyroid C-cell tumors has not been determined. MOUNJARO is contraindicated in patients with a personal or family history of MTC or in patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).”
Verbatim from the Mounjaro FDA label (DailyMed SetID d2d7da5d-ad07-4228-955f-cf7e355c8cc0). The boxed warning is the FDA's most serious warning. Do not start Mounjaro without discussing your personal and family medical history with a licensed prescriber.
Serious Warnings & Precautions
Beyond the common reactions above, the Mounjaro label lists these serious risks (Section 5 Warnings & Precautions). They are less common but can be medically urgent — know the symptoms and when to seek care.
- Risk of thyroid C-cell tumors
- Acute pancreatitis
- Hypoglycemia with concomitant use of insulin secretagogues or insulin
- Hypersensitivity reactions
- Acute kidney injury due to volume depletion
- Severe gastrointestinal adverse reactions
- Diabetic retinopathy complications
- Acute gallbladder disease
- Pulmonary aspiration during general anesthesia or deep sedation
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Related deep-dives
For management steps and the underlying evidence on each symptom, read our dedicated articles:
- Mounjaro nausea: causes & management →
- Mounjaro constipation: causes & relief →
- Mounjaro dizziness: causes & management →
- Mounjaro fatigue: causes & management →
- Mounjaro hair loss & telogen effluvium →
- Mounjaro headaches: how common? →
- Mounjaro acid reflux & GERD →
- Can you drink alcohol on Mounjaro? →
- Tirzepatide diarrhea: mechanism & management →
- Tirzepatide & lean-mass / muscle loss →
- Mounjaro/Zepbound FDA prescribing info explained →
- GLP-1 side effects: what the trials showed →
- How long do GLP-1 side effects last? →
- GLP-1 side-effect questions answered →