GLP-1 Weight Loss Treatments: Common Side Effects and How to Manage Them

Written by Shereen Amin MRPharmS, UK-registered Pharmacist Prescriber and Medical Writer (GPhC 2073003)

Introduction

GLP-1 medicines, such as Wegovy and Mounjaro, are now widely prescribed for weight loss and Type 2 diabetes management. They work by slowing digestion, reducing appetite and helping to control blood sugar.

Like any new treatment, your body may take a little time to adjust. Many people notice mild side effects during the first few weeks or after a dose increase. The positive news is that most of these effects are temporary, predictable and easy to manage with the right approach.

This guide explains the most common side effects of GLP-1 medications, why they happen, and practical steps to minimise discomfort. Whether you’re just beginning treatment or stepping up your dose, understanding what’s normal can help you stay confident and comfortable along the way, to stay on track and achieve the best results.

In this article

• Why GLP-1 medicines cause side effects
• Common GLP-1 side effects
• Patient reported side effects
• How to reduce GLP-1 side effects before they start
• When to speak to a healthcare professional
• GLP-1 side effects FAQs
• Reporting side effects to the MHRA (Yellow Card scheme)
• References
• Conclusion

Why GLP-1 medicines cause side effects

GLP-1 receptor agonists mimic a natural hormone that slows stomach emptying. This is one of the main ways these medicines reduce appetite and support weight loss. However, because food stays in the stomach for longer, symptoms such as nausea, bloating, and fullness can occur, especially early in treatment or after dose increases.

GLP-1 medications can also affect hydration and appetite cues. As your body adjusts, these symptoms typically settle within a few days or weeks. Knowing why side effects develop makes them easier to manage.

Common GLP-1 side effects

1. Nausea

Nausea is the most common GLP-1 side effect, particularly during the first two to four weeks of treatment or after increasing the dose.

How to manage nausea

• Eat small, frequent meals.
• Avoid high-fat, greasy, spicy or strong-smelling foods.
• Try ginger, peppermint or fennel tea, or sugar-free mints.
• Sip fluids between meals instead of with them.
• Avoid lying down immediately after eating.
• Take a short walk for fresh air.
• Speak to the Medy Clinical Team if nausea is severe or persistent.

2. Vomiting

Vomiting may occur alongside nausea, particularly with heavy meals or stepping up your dose too quickly.

How to manage vomiting

• Use the same strategies as for nausea.
• Take small sips of water or electrolyte solutions.
• Choose bland foods such as toast, crackers or plain rice.
• Avoid alcohol until symptoms settle.
• Seek medical advice if vomiting lasts more than 24 hours.

3. Diarrhoea

Diarrhoea often appears early in treatment and calms as the body adapts.

How to manage diarrhoea

• Drink plenty of fluids.
• Avoid caffeine, alcohol and high-fat foods.
• Eat simple foods such as rice, bananas and yoghurt.
• Consider loperamide or oral rehydration sachets.
• Seek medical attention if symptoms persist or if dehydration develops.

4. Constipation

Constipation can happen due to slower digestion and reduced food intake.

How to manage constipation

• Increase fibre gradually with wholegrains, fruit and vegetables.
• Stay well hydrated.
• Add light exercise, such as walking.
• Consider fibre supplements or mild laxatives.
• Seek help if symptoms persist or if there is blood in your stools.

5. Bloating and indigestion

Slower stomach emptying may cause bloating or early fullness/discomfort.

How to manage bloating

• Eat slowly and chew food thoroughly.
• Avoid fizzy drinks and chewing gum.
• Choose smaller portions.
• Try drinking peppermint tea or taking over-the-counter simethicone-based products.
• Reduce high-fat meals.

6. Injection site reactions

Redness, itching or small lumps can occur where GLP-1 medicines are injected.

How to manage injection site reactions

• Rotate injection sites.
• Allow medication to reach room temperature before injecting.
• Follow proper injection technique.
• Use antihistamines or antihistamine cream if appropriate.
• Seek help if symptoms worsen or spread.

7. Headache

Headaches may occur due to dehydration or reduced calorie intake.

How to manage headaches

• Drink water regularly.
• Eat balanced meals.
• Avoid skipping meals.
• Use simple pain relief such as paracetamol or ibuprofen.
• Seek help if headaches persist or cause vision changes.

8. Fatigue and low energy

Fatigue is common in the first few weeks of treatment.

How to manage fatigue

• Ensure your meals include enough calories.
• Stay hydrated.
• Prioritise sleep.
• Add gentle exercise.
• Seek advice if fatigue continues.

9. Indigestion and heartburn

Some people experience heartburn or acid reflux due to slower stomach emptying.

How to manage indigestion and heartburn

• Eat smaller meals.
• Avoid lying down after eating.
• Reduce trigger foods such as tomatoes, coffee, citrus, chocolate and high-fat meals.
• Avoid eating late at night.
• Consider antacids or alginate-based products.
• Seek help if symptoms interfere with sleep or persist.

10. Less common but important side effects

Some GLP-1 side effects are rare but require urgent attention.

• Pancreatitis: severe abdominal pain radiating to the back, nausea or vomiting
• Gallbladder issues: abdominal pain, fever, yellowing of skin or eyes
• Allergic reactions: swelling, difficulty breathing or widespread rash

Seek urgent help if any of these symptoms occur.

Patient-reported side effects

Sulphur burps

Some people notice burps with a sulphur-like smell caused by slower digestion or changes in gut bacteria.

How to manage

• Avoid very high-protein meals.
• Eat smaller meals.
• Stay hydrated.
• Reduce alcohol and fizzy drinks.
• Consider probiotics.
• Seek help if symptoms persist.

Alopecia

Occasional hair shedding can occur with rapid weight loss or lower nutrient intake.

How to manage

• Maintain adequate protein and iron intake.
• Avoid harsh hair treatments or tight styles.
• Seek advice if hair loss becomes significant.

Irregular menstrual bleeding

Some women experience cycle changes as their weight and metabolism change.

How to manage

• Track cycle patterns.
• Maintain healthy nutrition.
• Seek help for heavy or prolonged bleeding.

How to reduce GLP-1 side effects before they start

• Follow a gradual dose escalation plan with the Medy Clinical Team.
• Eat mindfully and avoid skipping meals or undereating.
• Stay hydrated throughout the day.
• Limit alcohol.
• Track your symptoms.
• Attend regular reviews with the Medy Clinical Team.

When to speak to a healthcare professional

Speak to a clinician if:

• Symptoms do not improve
• Side effects affect daily life
• You are unsure about dose increases
• Symptoms worsen

The Medy Clinical Team can help adjust dosing or provide support.

GLP-1 side effects FAQs

How long do GLP-1 side effects last?

Most settle within days to weeks. Contact the Medy Clinical Team if they continue.

Can diet changes help?

Yes. Smaller meals, reduced fat and consistent hydration can be really beneficial.

Are sulphur burps and hair loss normal?

They are reported but less common. They can usually be managed with lifestyle adjustments.

When should I be worried?

Seek urgent help for severe abdominal pain, jaundice (yellowing of the skin or eyeballs), breathing difficulty or facial swelling.

Reporting side effects to the MHRA (Yellow Card scheme)

If you experience or suspect side effects, you can report them to the MHRA through the Yellow Card scheme.

Reporting side effects to the MHRA helps them to identify new or rare reactions, improves medicine safety monitoring, and supports patient protection across the UK.

Anyone can submit a report, including clinicians and patients. You can report online, via the app or ask the Medy Clinical Team to do this for you.

Conclusion: managing GLP-1 side effects for better results

GLP-1 medications such as Wegovy and Mounjaro are powerful tools for weight loss and diabetes management. Side effects are common, particularly at the start of treatment, but most are temporary and manageable. For personalised support or dosing guidance, speak to the Medy Clinical Team.

References

1. Wegovy 2.4 mg solution for injection in pre-filled pen. Summary of Product Characteristics. Electronic Medicines Compendium (EMC). Accessed November 2025. ↩
2. Mounjaro solution for injection in pre-filled pen. Summary of Product Characteristics. Electronic Medicines Compendium (EMC). Accessed November 2025. ↩
3. Mehrtash F, Dushay J, Manson JE. Integrating Diet and Physical Activity When Prescribing GLP-1s. JAMA Internal Medicine. 2025;185(9):1151–1152. doi:10.1001/jamainternmed.2025.1794 ↩
4. Mozaffarian D, Agarwal M, Aggarwal M, Alexander L, Apovian CM, Bindlish S, Bonnet J, Butsch WS, Christensen S, Gianos E, Gulati M, Gupta A, Horn D, Kane RM, Saluja J, Sannidhi D, Stanford FC, Callahan EA. Nutritional priorities to support GLP-1 therapy for obesity. Obesity (Silver Spring). 2025;33(8):1475–1503. doi:10.1002/oby.24336 ↩
5. Yellow Card Scheme. Medicines and Healthcare products Regulatory Agency (MHRA). Accessed November 2025. ↩