A day on a GLP-1 medication: a routine for a calmer stomach

It's 7am, and breakfast doesn't sound appealing. By lunch, a few bites feel like a full meal. By evening, you're wondering why you haven't had a bowel movement in two days. If you've started a GLP-1 medication, such as semaglutide or tirzepatide, this may sound familiar.

Stomach side effects are the most common complaint with these medications. Here's what the research shows, followed by a practical routine for the day. It isn't a substitute for your prescriber's instructions.

First, what to expect

In pooled data from three trials of semaglutide 2.4 mg, nausea affected 43.9% of participants compared with 16.1% on placebo. Diarrhea affected 29.7%, vomiting 24.5% and constipation 24.2%. Most of these side effects were mild to moderate and temporary, and they were most common during or shortly after dose increases. Only 4.3% of people stopped treatment because of them (Wharton et al., 2022).

Tirzepatide showed a similar pattern. In its large obesity trial, gastrointestinal side effects were the most common, were mostly mild to moderate, and occurred primarily during the dose-escalation period (Jastreboff et al., 2022). A systematic review of 26 trials in adults without diabetes, 72% of them women, found gastrointestinal side effects in 47% to 84% of people taking these medications, while serious adverse events were rare (Moiz et al., 2025).

A multidisciplinary expert panel has published practical recommendations for reaching the maintenance dose and for easing nausea, vomiting, diarrhea and constipation along the way (Gorgojo-Martínez et al., 2022). The routine below follows that kind of everyday advice.

Morning: start small and hydrate

• Drink first. Start with a glass of water and keep sipping through the morning, especially if you've had vomiting or diarrhea.
• Choose a small, plain breakfast. A boiled egg with toast, or yogurt with a spoonful of oats, often sits better than a large or greasy meal.
• Eat slowly and stop at the first sign of fullness. On these medications, the gap between satisfied and too full can be very short.

Midday: smaller portions, less fat

• Serve a smaller portion. Plan for an amount you can finish comfortably, and save the rest for later.
• Keep lunch lighter in fat. Lean protein, cooked vegetables and a modest serving of grains are usually easier to handle than fried or rich foods.
• Take a short walk after eating, if you can. Ten minutes is enough to make it a habit.

Afternoon: stay ahead of constipation

• Keep drinking. Eating less food also means taking in less of the water that food provides.
• Add fiber gradually, from vegetables, fruit, oats or a supplement your clinician recommends. Big jumps can add to bloating.
• Snack small if you're hungry. A piece of fruit or a few crackers can prevent a large, uncomfortable meal later.

Evening: light and early

• Make dinner your lightest meal, and try to finish a few hours before bed.
• Stay upright after eating. Lying down on a full stomach can make reflux and nausea feel worse.
• Go easy on alcohol and fizzy drinks, which can add to bloating and discomfort.

Dose increases and procedures: plan ahead

• Expect symptoms to flare in the days after a dose increase, and plan simpler meals for that stretch.
• Tell your prescriber if side effects are hard to manage. Adjusting how the dose is increased is sometimes an option, and that's their call to make with you.
• Keep a simple log of symptoms, bowel movements and fluids, so you can report patterns rather than impressions.

Before any procedure, speak up. Tell your care team you take a GLP-1 medication before an endoscopy, colonoscopy or any procedure with sedation or anesthesia. In a retrospective study of 404 upper endoscopies, food or excess fluid remained in the stomach despite standard fasting in 24.2% of patients who had taken semaglutide in the previous 30 days, compared with 5.1% of those who hadn't (Silveira et al., 2023).

The semaglutide group in that study was small, just 33 patients. Still, findings like this are why procedure teams want to know, and they'll tell you whether anything needs to change beforehand.

When to call your doctor

• Severe abdominal pain that doesn't go away, with or without vomiting
• Vomiting that keeps you from holding down fluids, or signs of dehydration such as dizziness or very dark urine
• No bowel movement for several days along with a swollen belly, vomiting or being unable to pass gas
• Blood in your stool or black stools
• Side effects that make it hard to eat enough or to keep taking your medication

Sources

1. Wharton S, Calanna S, Davies M, et al. Gastrointestinal tolerability of once-weekly semaglutide 2.4 mg in adults with overweight or obesity, and the relationship between gastrointestinal adverse events and weight loss. Diabetes Obes Metab. 2022;24(1):94-105. PMID 34514682
2. Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide once weekly for the treatment of obesity. N Engl J Med. 2022;387(3):205-216. PMID 35658024
3. Moiz A, Filion KB, Toutounchi H, et al. Efficacy and safety of glucagon-like peptide-1 receptor agonists for weight loss among adults without diabetes: a systematic review of randomized controlled trials. Ann Intern Med. 2025;178(2):199-217. PMID 39761578
4. Gorgojo-Martínez JJ, Mezquita-Raya P, Carretero-Gómez J, et al. Clinical recommendations to manage gastrointestinal adverse events in patients treated with GLP-1 receptor agonists: a multidisciplinary expert consensus. J Clin Med. 2022;12(1):145. PMID 36614945
5. Silveira SQ, da Silva LM, de Campos Vieira Abib A, et al. Relationship between perioperative semaglutide use and residual gastric content: a retrospective analysis of patients undergoing elective upper endoscopy. J Clin Anesth. 2023;87:111091. PMID 36870274

This article is for general information and isn't medical advice. Follow your prescriber's instructions for GLP-1 medications, and talk to them before changing your dose, schedule or diet plan.