Mounjaro side effect
Diarrhea affects roughly 15–30% of GLP-1 users, typically in the first 4–8 weeks. It tends to alternate with constipation as your gut adapts to slower transit.
In trial — Mounjaro
23%
In trial — placebo
7.3%
Severity
moderate
Source: SURMOUNT-1 (Jastreboff et al., NEJM 2022)
GLP-1 medications change gut motility unpredictably — for some people the result is faster small-bowel transit (diarrhea), for others slower colonic transit (constipation). Many people swing between the two during titration.
Timeline
Onset within the first 1–2 weeks of starting or escalating; most cases resolve within 4 weeks at a stable dose.
Call your prescriber if:
Yes — loperamide (Imodium) has no known interaction with GLP-1 medications. Use the lowest effective dose for acute episodes; avoid daily long-term use without prescriber input.
GLP-1 drugs slow gastric emptying and affect gut motility unpredictably. Different segments of the GI tract respond differently — your stomach and small intestine may slow (constipation) while your colon speeds up (diarrhea), or vice versa. This usually stabilizes by month 2–3.
This is general drug information, not medical advice. Talk to a licensed clinician before changing your dose, stopping, or starting any over-the-counter remedy.
Drug-specific guides for the other commonly reported reactions on Mounjaro.
Side effect
Nausea is the most common GLP-1 side effect. It usually shows up in the first week of a new dose, peaks within…
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Vomiting is less common than nausea — about 10–15% of GLP-1 users experience it, usually in the first month of…
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Constipation is reported by 15–25% of patients on GLP-1s. Slowed gastric emptying plus reduced food intake mea…
Read