Introduction

GLP-1 receptor agonists (GLP-1 RAs) like liraglutide, dulaglutide, and semaglutide are often prescribed when treating type 2 diabetes and obesity because of their innate ability to mediate weight loss and actively help maintain a healthy blood sugar level in the body.¹ This does not come without a significant cost, as their positive therapeutic effects are regrettably followed by negative gastrointestinal (GI) problems in addition to a myriad of other issues that result in reduced quality of life for patients.¹ This report will use results from clinical trials and pharmacovigilance data to provide an outline for the prevalence, timing, and overall management options for these side effects. 

Most common side effects

Gastrointestinal symptoms: nausea, vomiting, diarrhoea, and constipation 

30-50% of patients in the early stages of treatment said that they suffered from nausea.² For instance, in 2021, a trial for semaglutide at 2.4 mg found that an alarming 44.2% of participants felt nauseous, so much so that 4.5% of participants chose to stop taking the treatment altogether due to the severity of the discomfort they had to endure.² Semaglutide works by slowing down gastric emptying and instead activates GLP-1 receptors in the brainstem. Between 15-30% of patients vomit as a result, in addition to 13-20% of patients suffering from diarrhoea, whereas only 10-15% of patients report constipation alone with agents such as dulaglutide instead.¹ In 2024, a drug safety alert in the UK brought to light the dangerous levels of dehydration due to constant vomiting and diarrhoea, which led to hospitalisation in 2.1% of cases.³

We know that over 80% of people who start to use GLP-1s experience side effects in the GI, as that is the location of the body’s initial reaction to the medication, trying to reduce digestion speeds.³ 

Nausea is the most common side effect that leaves you with a feeling of slight motion sickness and a persistent, uncomfortable feeling that you would usually get from eating something that doesn't particularly agree with your stomach. There are a couple of things you could do to ease these symptoms, one is to eat less exotic foods like toast or rice in smaller portions throughout the day instead of your average three meals a day. Another thing you could do is to settle your stomach by sipping slowly on ginger tea and electrolyte drinks in addition to timing your doses strategically to be at times when you sleep to get through the brunt of the nausea instead of throughout the day. All these avenues of pain management aim to help you reduce the load on your GI and, in turn, the very side effects that afflict you. 

Vomiting and diarrhoea tend to follow nausea but tend to improve after a couple of weeks. If these side effects pose a particularly hard hurdle for you in particular, not to worry, as there are ways to combat them, too. Dehydration is something you must be wary of by actively staying hydrated to help prevent fatigue and dizziness from aggressive release of fluids due to the symptoms. Avoiding foods that are too spicy and greasy complicates digestion, so a good alternative is foods like bananas and broth-based soups that are easy to digest. 

Constipation due to irregular bowel movements and slower digestion can be fixed by an increase of fibre in your diet by adding oats or steamed vegetables to your meals, as your stomach settles, followed by a daily 15-minute walk helps to stimulate healthy bowel movements as well. 

Injection site reactions

5-10% of users witnessed reddening of the skin due to inflammation (erythema) that then led to an irritating itchy feeling (pruritus), making them want to pick at it and scratch at the site of injection, which was often linked back to the presence of preservatives like metacresol.¹ A case study in 2025 saw that periodically changing the site of injection between the thighs and the stomach region can reduce these reactions by 62%.⁴

Two ways to minimise discomfort are to change the site of injection between your stomach, thighs, and upper arms to give those areas some time to recover from being constantly pierced. The other way is to actually wash the area with some soap and water instead of alcohol/ antiseptic wipes, as they can be a source of irritation or an allergic response. 

Rare but serious risks

A sudden inflammation of the pancreas (acute pancreatitis) was recorded in 0.3-0.5% of patients; those who had already been diagnosed with hypertriglyceridemia were more likely to suffer from acute pancreatitis.¹ Gallbladder issues, such as gallstones within the gallbladder (cholelithiasis), were seen in 1.5-2% of long-term users due to reduced gallbladder motility.⁴ Exenatide has also been linked to 0.8% of users suffering from the blockage of food in the intestines (bowel obstructions) and 0.5% of users undergoing stomach paralysis (gastroparesis) when used chronically over time.¹

If you find that you constantly suffer from severe abdominal pain, abnormal yellowing of the skin and eyes (jaundice), or alarming discolouration in your urine and stool, a doctor should be contacted immediately, as these are symptoms related to internal bleeding and organ failure.

Timing and severity

Onset and duration

• Early phase (Weeks 1-4): If the dosage used increases, the adverse gastrointestinal symptoms will also increase. A trial held in 2021 concluded that 68% of nausea cases had been resolved no later than a month as the patients became accustomed to the semaglutide in their bodies.² You could effectively liken it to your body getting used to a new exercise regimen; you have to give your body some time to get used to the new strains you are subjecting it to
• Maintenance phase (Weeks 5+): Symptoms are typically seen to decrease overall, but can reappear if the dosage rises. This is evident with liraglutide, users have been seen to experience 23% fewer GI events after 3 months in comparison to the first month of use
• Delayed risks (6+ Months): Ongoing monitoring is crucial as serious complications, such as the previously mentioned gallbladder disease or pancreatitis, are more likely to become apparent after prolonged exposure to these GLP-1s.³ Regular meetings with your healthcare provider are extremely important to get ahead of these issues

Risk factors

• Sex: Women have been reported to be 1.7 times more likely to report nausea than men¹
• Dose: Stronger medications like semaglutide at 2.4 mg increased the risk of nausea by a staggering 33% when compared to a dose of 1.0 mg²
• Other medications: If you were to combine GLP1-RAs with sulfonylureas, the risk of an increase in hypoglycemia rises by 12-18%¹
• Pre-existing conditions: If you already suffer from a history of pancreatitis or gallbladder diseases, taking the drugs may exacerbate these issues
• Dehydration: Not drinking enough fluids can make GI symptoms even worse and strain the kidneys⁵

Practical prevention tips 

Start slow 

You should start with the lowest dose possible and then increase gradually, as this approach will give your body the best chance to adjust and reduce nausea. Semaglutide can be taken at a dose of 0.25 mg per week, and after one month, it can be increased to 0.5 mg.

Dietary modifications for comfort

Drinking a cup of water 30 minutes before eating a meal helps ease digestion, making it easier to avoid overeating. As you are avoiding foods laden with grease and fats, taking the time to eat meals that contain high amounts of lean protein will help digestion, too. Finally, as you are eating, be mindful of your chewing as you should do this slowly and mindfully, while also stopping yourself when you are near complete fullness at around 80% to avoid full discomfort in your body.

Lifestyle tweaks

Developing a routine after every injection that has you staying upright for a minimum of 30 minutes does wonders to reduce the effects of nausea and reflux. You could even incorporate that with a form of meditation or reading, essentially an anxiety and stress reducing activity that reduces anxiety. Anxiety can amplify GI symptoms, so a short walk can have the same effects when trying to calm your mind and body.

Summary 

To conclude, GLP-1 RAs have numerous metabolic benefits but must be managed carefully to mitigate their gastrointestinal and injection-related effects. The potency of these side effects is directly related to the dosage used and the medical history of each individual, but severe complications remain a rarity. Staying proactive is the key, as changing your diet, increasing water intake, and gradually increasing the dosage all make the process a much more tolerable experience. Most side effects are temporary, but keeping your healthcare provider informed of ongoing symptoms, along with support groups, can offer even more encouragement and tips to help. Don't forget that GLP-1s are a long-term tool, and managing side effects is a part of the process.