GLP-1s: What are they and are there side effects?

GLP-1 medications are gaining a lot of attention lately, not just for managing type 2 diabetes but also for their role in weight loss. Let’s explore what they are, how they work, and the side effects to keep in mind.

What are GLP-1s?

GLP-1 receptor agonists are a class of medications originally developed to help manage type 2 diabetes. More recently, they have gained popularity for their role in weight loss. These medications mimic the natural hormone glucagon-like peptide-1 (GLP-1), which is involved in regulating blood sugar levels and appetite. By delaying stomach emptying and increasing feelings of fullness, GLP-1 medications can help reduce overall food intake, supporting weight loss.

The different types of GLP-1s

There are different types of GLP-1 receptor agonists, each with slightly different properties. A healthcare professional will consider your health needs, including other health conditions, when choosing the best one. The main types of GLP-1s available in Australia are semaglutide, liraglutide and tirzepatide and these are taken as an injection.

Side effects of GLP-1s

GLP-1 receptor agonists may cause both long and short term side effects.

Potential short-term side effects:

• Nausea and vomiting: These are among the most common side effects of GLP-1 medications, especially at the start. This happens because they slow down how quickly food moves through your stomach, which can reduce appetite and sometimes lead to that uneasy feeling.
• Constipation: Some individuals may experience this due to changes in the gut.
• Reduced appetite: Another common side effect, so it's important to stay nourished while on these medications to maintain energy, muscle mass, and overall health.
• Reflux (or heartburn): This may occur when using GLP-1 medications, especially as they slow digestion.
• Belching (burping): With the slowing of digestion, frequent belching (or burping) can become more frequent. This is due to a build up of sulfur, which can smell and taste like rotten eggs.

Potential long-term effects:

• Muscle and bone density loss: This can occur due to rapid weight loss. It’s important to change lifestyle habits to preserve muscle mass and protect bones.
• Rapid weight loss: This may also increase the risk of gallbladder issues like gallstones.

How can I deal with the side effects?

• Nausea: Avoid strong smells and spicy or greasy foods. Eating small, frequent meals and incorporating ginger products or peppermint tea may help. There are also over-the-counter nausea relief products you can try.
• Vomiting: Smaller, frequent meals may help here as well. Eat foods that are easy to tolerate such as soups and broths, rice with well cooked vegetables, ripe fruit without skin and crackers. Take small sips of water to ensure you stay hydrated.
• Constipation: Stay hydrated and increase fibre intake with wholegrains, fruits, and vegetables, while incorporating gentle physical activity. You may also want to try a fibre supplement for an additional fibre boost.
• Low appetite: While reduced hunger is expected, ensure adequate nutrition by focusing on nutrient-dense foods like milk, yoghurt, nut butter, eggs and meat if you can tolerate it. Smoothies and soups with added protein powder can be helpful.
• Reflux: Avoid large meals, fatty foods, and lying down immediately after eating. Keeping meals light and sitting upright for at least 30 minutes after eating can help. Avoid trigger foods like spicy dishes, caffeine, or carbonated drinks. There are also reflux and indigestion tablets that can help to provide relief.
• Belching: Drink plenty of water to help flush out sulfur and incorporate pre and probiotics in your diet to support a healthy balance of bacteria in the gut. 
• Muscle and bone loss: Strength training and consuming adequate protein, calcium, and vitamin D are essential. It’s important to work with a healthcare professional to ensure you’re looking after your muscles and bones.
• Gallstones: Stay hydrated and include healthy fats at main meals to help reduce this risk.

When should I see a healthcare professional?

When taking GLP-1 medications, it’s important to see a healthcare professional if you are experiencing:

• Severe nausea or vomiting that prevents you from staying hydrated.
• Persistent or worsening constipation that does not improve with dietary changes.
• Symptoms of gallstones, such as severe abdominal pain or jaundice.
• Signs of low blood sugar, such as dizziness, confusion, or excessive fatigue.
• Unexplained muscle weakness or significant changes in bone health.
• Any other persistent side effects that are not improving.

The bottom line

GLP-1 medications come with potential side effects and these can be largely managed with dietary adjustments and lifestyle strategies. If you’re considering a GLP-1 medication and struggling with persistent side effects, it’s important to speak with your healthcare professional to ensure you’re taking steps to maintain overall health while on treatment.

Related reads:

• What is a healthy weight?
• Why your weight isn't a measure you should use to define yourself

Reviewed by the Healthylife health experts April 2025.