Mounjaro Side Effects: What to Expect
Every reaction the tirzepatide trial program recorded, alongside the boxed warning and the Section 5 risks its FDA label carries.
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Most Common Mounjaro Side Effects
Every reaction the Mounjaro FDA label records, showing how often it appeared among tirzepatide-treated patients and how often it appeared on placebo. The figures are taken from the label's Section 6, DailyMed SetIDd2d7da5d-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, read on 2026-05-31. Treat this as a summary — the full label is the document, and a prescriber is the person to discuss it with.
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).”
Quoted word for word from the Mounjaro FDA label (DailyMed SetID d2d7da5d-ad07-4228-955f-cf7e355c8cc0). Nothing the FDA issues carries more weight than a boxed warning. Your own history and your family's both need to be on the table before you start Mounjaro, and that means talking to a licensed prescriber.
Serious Warnings & Precautions
Past the everyday reactions above, Section 5 of the Mounjaro label sets out these serious risks. They arrive far less often, and some of them need care the same day — which is why the symptoms are worth knowing 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
Compare every Mounjaro provider
Every warning above is something a prescriber screens for before writing anything. Current price, verification status, product form and the states each seller ships to are all on one screen.
Related deep-dives
What to do about each symptom, and the evidence underneath it, is covered here:
- How long GLP-1 side effects last →
- Hair loss and muscle loss on a GLP-1 →
- Pancreatitis and gallbladder risk →
- What the thyroid cancer warning rests on →
- Eye risk: NAION and retinopathy →
- Drinking on a GLP-1 →
- What happens when you stop →
- Where to inject, and why the site matters →
- Tirzepatide side effects over the long run →
- Side effects reported on compounded tirzepatide →