Question explored with the scientific record
Conversation so far
- 1 what are the risks of these new glp-1 drugs?
- 2 what about side effects, such as problems with skin, mood etc.
- 3 what about digestive problems - diarhoea constipation etc.
Answered on this page ↓
what about digestive problems - diarhoea constipation etc.
The short version: diarrhea and constipation are common on GLP-1 drugs, they are the most predictable side effect of the class, and they are usually worst in the first weeks.
The mechanism is simple. These drugs slow the stomach and gut, so food sits longer. That produces nausea, vomiting, diarrhea, and constipation together [7]. A 2022 review of high-dose GLP-1 drugs and dual agonists found gut side effects in 30% to 70% of patients, mostly in the first two weeks, mostly mild to moderate, and mostly transient [2]. Discontinuation because of gut side effects ran 3% to 4% [2]. A 2025 real-world study of liraglutide in obesity found any adverse event in 48% of patients, with nausea and vomiting the most common, and 22.9% of discontinuations blamed on gut tolerance [5].
The numbers vary a lot by drug and dose, which matters if you are choosing one.
| Drug (monotherapy) | Diarrhea | Nausea |
|---|---|---|
| Exenatide twice daily | under 2% | 8% |
| Exenatide once weekly | 11% | 11% |
| Liraglutide | 17% | 28% |
Those are from a 2013 review [1]. In a head-to-head trial, liraglutide caused diarrhea in 59 patients versus 28 on exenatide once weekly [6]. Tirzepatide caused more gut side effects than semaglutide, with diarrhea odds roughly 3.6 to 8.3 times placebo in the SURMOUNT trials [8]. Retatrutide, a triple agonist, caused gut effects in 13% to 50% of users, with 16% to 17% quitting the drug [4].
Constipation is real but less quantified in these records. It appears in the side-effect lists [7][4] but no record here gives a clean rate for it alone. That is a gap in what I can see, not a finding that it is rare.
One serious downstream risk: severe vomiting and dehydration can trigger kidney injury. A case report describes a 70-year-old on metformin who developed life-threatening lactic acidosis after rapid liraglutide uptitration caused severe vomiting and dehydration [3]. That is one patient, but the mechanism is real and worth knowing if you take metformin or have kidney problems.
My call: expect gut side effects, especially in the first weeks, and titrate slowly; if diarrhea or constipation is severe or persistent, that is a reason to talk to your doctor about dose or drug choice, not something to push through silently. Confidence: moderate on the rates, low on constipation specifically.
Sources used 8
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Practical Use of Glucagon-Like Peptide-1 Receptor Agonist Therapy in Primary Care
GLP-1 receptor agonists offer distinct benefits and limitations for type 2 diabetes, and individualized selection among exenatide BID, exenatide QW, and liraglutide plus patient education can improve acceptance and self-management.
DOI: 10.2337/diaclin.31.4.148 -
Efficacy and safety of high‐dose glucagon‐like peptide‐1, glucagon‐like peptide‐1/glucose‐dependent insulinotropic peptide, and glucagon‐like peptide‐1/glucagon receptor agonists in type 2 diabetes
In this systematic review, high-dose GLP-1 RAs and especially tirzepatide increased proportions of patients with type 2 diabetes reaching HbA1c <7% (up to 80%-97%) and weight-loss targets, with gastrointestinal side effects in 30%-70% that were mostly mild and transient.
DOI: 10.1111/dom.14640 -
Metformin-associated lactic acidosis precipitated by liraglutide use: adverse effects of aggressive antihyperglycaemic therapy
A 70-year-old man on metformin developed life-threatening metformin-associated lactic acidosis after rapid liraglutide uptitration caused severe vomiting, dehydration and acute kidney injury.
DOI: 10.1136/bcr-2018-227102 -
Retatrutide As a Novel Treatment for Obesity and Type 2 Diabetes
Retatrutide, a once-weekly GLP-1/GIP/glucagon triple agonist, produced substantial dose-related weight loss and HbA1c reduction in two phase 2 trials in obesity and type 2 diabetes, but caused frequent gastrointestinal adverse effects, high discontinuation rates, and heart-rate/…
DOI: 10.31579/2768-0487/111 -
Comprehensive analysis of real-world data on liraglutide treatment in patients with obesity: a multicenter national study
A large multicenter retrospective real-world study in Türkiye assessing the effectiveness, safety, metabolic effects, and reasons for discontinuation of liraglutide in adults with obesity/overweight, showing substantial weight loss and metabolic improvements but notable adverse …
DOI: 10.1186/s40001-025-02836-5 -
Exenatide once weekly versus liraglutide once daily in patients with type 2 diabetes (DURATION-6): a randomised, open-label study
This study compares the efficacy and safety of exenatide once weekly versus liraglutide once daily in patients with type 2 diabetes, finding that liraglutide resulted in greater reductions in glycated hemoglobin (HbA1c) and weight loss, but with more gastrointestinal side effect…
DOI: 10.1016/S0140-6736(12)61267-7 -
Therapeutic Boon or Hidden Bane? Semaglutide for Weight Loss in Non-diabetics
A narrative review concludes that semaglutide achieves substantial weight loss and cardiovascular benefits in nondiabetic patients, but high cost, gastrointestinal and rare serious side effects, and misuse risks require comprehensive obesity-care strategies.
DOI: 10.29328/journal.jcmhs.1001080 -
Efficacy and Safety of Tirzepatide for Weight Management in Non-Diabetic Obese Individuals: A Narrative Review
A narrative review synthesizing current clinical evidence on the efficacy and safety of tirzepatide for weight management in non-diabetic obese adults, showing substantial weight loss and cardiometabolic benefits across multiple SURMOUNT trials with generally GI-dominant adverse…
DOI: 10.3390/obesities5020026