Common Side Effects and How to Manage Them

GLP-1 receptor agonists such as semaglutide, tirzepatide, and liraglutide are among the most effective treatments for weight management and metabolic health.

Like all medications, they can cause side effects, particularly when you first start or increase your dose. Most reactions are mild and improve as your body adapts. Understanding why these effects occur and how to manage them can make treatment much more comfortable.

GLP-1 receptor agonists slow digestion and signal to the brain that you are full sooner. These effects are central to how the medicine works but can also lead to symptoms such as nausea, constipation, or fatigue in the early weeks.

The good news is that most people find these symptoms fade over time as their body becomes used to the medication.

Nausea

Nausea is the most frequent side effect, especially when increasing your dose. It occurs because food leaves the stomach more slowly.

Tips to manage nausea:

• Eat smaller meals and chew slowly.
• Avoid rich, spicy, or greasy foods.
• Try cold foods like yogurt, smoothies, or soups if warm meals trigger nausea.
• Stay upright after eating and avoid lying down immediately.
• If symptoms persist, your clinician may pause dose escalation or recommend anti-nausea medication.

Advice from Laura Reed, Health Coach:
Many of our members find that “bland and beige” meals such as porridge, rice, or crackers help during dose adjustment weeks. Eating earlier in the evening and sipping water or ginger tea slowly throughout the day can also ease nausea.

Constipation

Constipation is common because GLP-1 medicines slow bowel movement along with digestion.

Tips to manage constipation:

• Increase fluid intake and aim for at least six to eight glasses of water daily.
• Add fibre gradually through fruit, vegetables, oats, or psyllium husk.
• Stay physically active, as movement helps bowel function.
• Avoid over-relying on stimulant laxatives such as sennakot; a mild osmotic laxative for example lactulose may be safer if needed.

Advice from Laura Reed, Health Coach:
Many people benefit from a daily glass of water with chia seeds or a small bowl of kiwi or prunes. Building a short morning walk into your routine also helps stimulate digestion naturally.

Diarrhoea

Some people experience loose stools, particularly after dose increases. This usually settles as your digestive system adjusts.

Tips to manage diarrhoea:

• Stay hydrated with water and oral rehydration salts if needed.
• Eat smaller, more frequent meals that are high in fibre  and avoid fatty or fried foods.
• Limit caffeine and artificial sweeteners.

Fatigue

Tiredness or low energy can occur in the first few weeks due to reduced calorie intake and fluid shifts.

Tips to manage fatigue:

• Ensure adequate hydration and electrolytes.
• Eat balanced meals with protein at each sitting.
• Get sufficient sleep and moderate physical activity.
• Avoid sudden, extreme calorie restriction on top of medication.

Advice from Laura Reed, Health Coach:
“It’s normal to feel a dip in energy when your appetite changes,” says Laura. “Your body is adjusting. Small, steady meals with protein and hydration make a big difference.”

Headache and Dizziness

Headaches may result from dehydration, reduced food intake, or low blood sugar in people taking diabetes medication.

Tips:

• Drink plenty of water.
• Avoid skipping meals, even if you feel less hungry.
• If you are taking insulin or other diabetes medication, monitor blood glucose levels.
• Taking regular paracetamol should help with any headaches and is safe to take with your medication.

Heartburn or Indigestion

A slower digestive process can occasionally lead to reflux or heartburn.

Tips:

• Avoid lying down after meals or eating late in the evening.
• Eat smaller portions and limit acidic or spicy foods.
• Your clinician may recommend a short course of antacid if symptoms persist.

Seek medical advice if side effects are:

• Severe or persistent beyond the first few weeks
• Accompanied by significant abdominal pain, vomiting, or dehydration
• Affecting your ability to eat or drink or you find you are passing alot less urine
• Associated with signs of pancreatitis or gallbladder disease (upper abdominal pain radiating to the back, fever, or jaundice)

Your clinician can adjust your dosage or schedule to help your body adapt more gradually.

Most people find that symptoms ease within four to six weeks, particularly once they stabilise at a maintenance dose. The goal is to make the process manageable so you can continue benefiting from the medication’s effects on appetite and metabolism.

Mild side effects are common when starting GLP-1 medications, but they are usually short-lived and manageable with the right approach. Hydration, small balanced meals, and gradual lifestyle adjustments make a significant difference. Your healthcare team can help tailor strategies so you remain comfortable and confident throughout treatment.

You can complete an online health assessment if you would like to explore whether GLP-1 treatment may be clinically appropriate for you – start the assessment.

Dr Abby Hyams completed her medical training in Bristol and has been a GP for 19 years, spending many of those as a partner in an NHS practice in Hemel Hempstead. She has a particular passion for supporting patients with weight loss and promoting positive behaviour change, helping individuals build sustainable habits that improve their long-term health and wellbeing.

This article is for general information only and should not be used for the diagnosis or treatment of medical conditions. Medic Spot Limited has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions. In the event of an emergency, please call 999 for immediate assistance.

There is no guarantee of a specific weight loss medication being prescribed. Clinicians will review your online questionnaire alongside other independently validated medical information about you and will recommend the most appropriate weight loss treatments for you based on your answers. In some cases, the clinicians may contact you for additional information. See Terms of Service for more information.