GLP-1 Weight Loss Medicines: What You Need to Know

Weight loss injections containing medicines such as semaglutide (Wegovy®) and tirzepatide (Mounjaro®) have gained significant attention in recent years. These medicines can help some people lose weight and improve obesity-related health conditions when used alongside healthy lifestyle changes.

GLP-1 medicines were originally developed to treat type 2 diabetes, but some are now licensed for weight management in people living with overweight or obesity.

What Are GLP-1 Medicines?

GLP-1 stands for glucagon-like peptide-1, a hormone naturally released by the gut after eating.

GLP-1 receptor agonists work by mimicking the effects of this hormone. They act on areas of the brain involved in appetite regulation, helping people feel fuller for longer and reducing hunger.

These medicines may help people:

• Feel less hungry
• Feel full sooner during meals
• Reduce food cravings
• Eat smaller portions
• Achieve gradual and sustainable weight loss
• Improve blood sugar control in people with type 2 diabetes

It is important to remember that these medicines are not a quick fix for weight loss. They work best when combined with healthy eating, regular physical activity, adequate sleep, and long-term lifestyle changes.

Which GLP-1 Medicines Are Available?

Several medicines that act on the GLP-1 pathway, either alone or in combination with other hormonal pathways

Wegovy® (Semaglutide)

Wegovy is administered as a once-weekly injection. The dose is increased gradually over several weeks to help minimise side effects and allow the body to adjust to treatment. Semaglutide is also available in other forms. Ozempic® is a weekly injection licensed primarily for type 2 diabetes, while Rybelsus® is a once-daily oral tablet licensed for type 2 diabetes.

Ozempic® (Semaglutide)

Ozempic contains the same active ingredient as Wegovy, semaglutide. In the UK, Ozempic is licensed primarily for the treatment of type 2 diabetes, alongside healthy eating and regular physical activity. Although weight loss can occur while taking Ozempic, it is not specifically licensed as a weight management treatment. Ozempic is administered as a once-weekly injection and requires gradual dose increases under medical supervision.

Mounjaro® (Tirzepatide)

Mounjaro contains tirzepatide, which works by activating both GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors.These hormones help regulate appetite, blood sugar levels and digestion. As a result, Mounjaro can reduce hunger, increase feelings of fullness and support weight loss.Mounjaro is given as a once-weekly injection and should be used alongside a healthy diet and regular physical activity.

How Do GLP-1 Medicines Work?

GLP-1 medicines support weight loss and blood sugar control through several mechanisms.

1. They Reduce Appetite

These medicines act on appetite centres in the brain, helping people feel less hungry and reducing food cravings.

2. They Slow Stomach Emptying

Food remains in the stomach for longer, helping people feel full for longer after eating.

3. They Improve Blood Sugar Control

GLP-1 medicines stimulate insulin release when blood sugar levels rise and help reduce excessive increases in blood glucose after meals.

4. They Reduce Calorie Intake

Because people often feel fuller sooner and remain satisfied for longer, they may naturally consume fewer calories throughout the day.

5. They Reduce Glucagon Production

Glucagon is a hormone that increases blood sugar levels. GLP-1 medicines reduce glucagon release when it is not needed, helping improve blood glucose control.

Who May Be Eligible for Treatment?

GLP-1 medicines may be considered for adults who:

• Have obesity
• Are overweight and have weight-related health conditions
• Have type 2 diabetes
• Have struggled to lose weight through lifestyle measures alone

Weight-related health conditions may include:

• High blood pressure
• Obstructive sleep apnoea
• Fatty liver disease
• Cardiovascular disease

A healthcare professional can assess whether these medicines are suitable based on an individual's medical history, weight and overall health.

How Effective Are GLP-1 Medicines for Weight Loss?

Results vary because not everyone responds to treatment in the same way. People who combine medication with healthy eating habits and regular physical activity generally achieve the best outcomes.

Large clinical trials have shown that GLP-1 medicines can lead to significant weight loss when used alongside lifestyle changes.

The STEP clinical trial programmer evaluated semaglutide in adults living with overweight or obesity. Participants taking semaglutide lost approximately 10% to 15% of their body weight on average over 68 weeks, compared with much smaller weight losses in those receiving placebo treatment.

Research has also shown that tirzepatide may achieve even greater weight loss in some patients, with average weight reductions exceeding 20% in clinical trials.

In addition to weight loss, studies have reported improvements in:

• Blood pressure
• Cholesterol levels
• Blood sugar control
• Waist circumference
• Physical function and quality of life

Studies have also shown that some people regain weight after stopping treatment. This suggests that obesity is often a long-term condition requiring ongoing management and healthy lifestyle habits.

How Quickly Do GLP-1 Medicines Work?

Many people notice a reduction in appetite within the first few weeks of treatment. Weight loss typically develops gradually over several months.

The amount of weight lost varies between individuals and depends on factors such as:

• Diet quality
• Physical activity levels
• Adherence to treatment
• Underlying health conditions
• Individual response to medication

Monitoring During Treatment

Regular reviews with a healthcare professional are important while taking GLP-1 medicines.

Monitoring may include:

• Weight and BMI
• Blood pressure
• Blood sugar measurements (for people with diabetes)
• Side effects
• Progress towards treatment goals

These reviews help ensure the medication remains safe and effective.

Common Side Effects

Most side effects affect the digestive system and often improve as the body adjusts to treatment.

Common side effects include:

• Nausea
• Vomiting
• Diarrhoea
• Constipation
• Indigestion
• Bloating
• Stomach discomfort
• Reduced appetite
• Burping
• Heartburn

These side effects are most likely to occur when starting treatment or increasing the dose.

Serious Side Effects

Serious side effects are uncommon but can occur.

Seek urgent medical attention if you develop any of the following:

Pancreatitis

Warning signs include:

• Severe upper abdominal pain
• Pain spreading to the back
• Persistent vomiting

Gallbladder Problems

Warning signs include:

• Pain in the upper right side of the abdomen
• Fever
• Jaundice (yellowing of the skin or eyes)

Severe Dehydration

Persistent vomiting or diarrhoea can lead to dehydration, particularly in older adults and those with other medical conditions.

Acute Kidney Injury

In some cases, severe dehydration may affect kidney function.

Severe Allergic Reactions

Seek emergency medical attention if you develop:

• Swelling of the face
• Swelling of the tongue or throat
• Difficulty breathing

Who Should Not Use These Medicines?

GLP-1 medicines may not be suitable for everyone.

They may be unsuitable for people with:

• A personal or family history of medullary thyroid carcinoma
• Multiple Endocrine Neoplasia Type 2 (MEN2)
• A previous serious allergic reaction to the medication
• Pregnancy
• Active pancreatitis

A healthcare professional should always assess suitability before treatment begins.

Can Weight Return After Stopping Treatment?

Yes.

Research has shown that some people regain weight after stopping GLP-1 medicines. Continuing treatment, together with healthy lifestyle habits, may help maintain weight loss.

For some individuals, obesity is a long-term health condition that may require ongoing treatment, similar to conditions such as high blood pressure or type 2 diabetes.

 

Frequently Asked Questions

Are the Injections Painful?

Most people experience little or no discomfort. The needles used for these injections are very small.

How Often Are the Injections Given?

Most injectable GLP-1-based medicines used for weight management are administered once weekly, although oral semaglutide tablets are also available for the treatment of type 2 diabetes.

Can I Drink Alcohol While Taking GLP-1 Medicines?

Moderate alcohol consumption may be acceptable for some people. However, excessive alcohol intake may worsen side effects and increase the risk of pancreatitis.

If you have diabetes or other health conditions, discuss alcohol consumption with your healthcare professional.

Do I Still Need Diet and Exercise?

Yes.

GLP-1 medicines work best when combined with:

• Healthy eating habits
• Regular physical activity
• Adequate sleep
• Behavioural and lifestyle changes

Can I Stop Taking the Medication Once I Reach My Goal Weight?

This varies from person to person. Some people may require long-term treatment to maintain weight loss, while others may be able to stop treatment under medical supervision.

Your healthcare professional can advise on the most appropriate approach for your individual circumstances.

Key Takeaways

• GLP-1 medicines help reduce hunger and increase feelings of fullness.
• Common medicines include Wegovy® (semaglutide for weight management), Ozempic® and Rybelsus® (semaglutide for type 2 diabetes), and Mounjaro® (tirzepatide).
• These medicines are most effective when combined with healthy eating, physical activity and long-term lifestyle changes.
• Clinical trials have demonstrated significant weight loss benefits in many patients.
• Most side effects affect the digestive system and improve over time.
• Some people may regain weight after stopping treatment.
• Treatment should always be started and monitored by a qualified healthcare professional.

Summary

GLP-1 medicines such as Wegovy® and Mounjaro® can help some people achieve significant weight loss and improve obesity-related health conditions. They work by reducing appetite, increasing feelings of fullness, slowing stomach emptying, and helping regulate blood sugar levels.

Clinical studies have shown that these medicines can support meaningful weight loss when combined with healthy eating, regular physical activity and long-term lifestyle changes. However, they are not suitable for everyone and should not be viewed as a quick fix for obesity.

As with all medicines, there are potential side effects and risks. Treatment should always be guided by a qualified healthcare professional, with regular follow-up to assess progress, manage side effects and determine whether treatment remains appropriate.

Disclaimer: This article is intended for general educational purposes only and should not be used as a substitute for professional medical advice, diagnosis or treatment. Weight-loss medications are not suitable for everyone. Always speak to your GP, pharmacist or another qualified healthcare professional before starting, stopping or changing any medication.