What Is the Best Injection for Weight Loss? (UK Guide)

According to a study on the prevalence of use and interest in glucagon-like peptide-1 receptor agonists for weight loss, approximately 1.6 million adults in Great Britain reported using a GLP-1 (glucagon-like peptide-1) or GLP-1/GIP (glucose-dependent insulinotropic polypeptide) medication.

The study proves that weight-loss medicine has become very popular, likely because losing weight is not easy for some people. You may need extra support on top of diet and exercise to see the results you want. But one question comes up time and again: what is the best injection for weight loss?

The answer is that it depends on what dosing schedule you prefer and what works for you. Different medications work in slightly different ways, and the right choice depends on your goals and medical history. It may also depend on your lifestyle.

In this guide, you’ll get a comprehensive comparison of the leading weight loss injections available in the UK to help you determine what's right for you.

What Are Weight Loss Injections?

Weight loss injections are prescription medications designed to help you lose excess weight by targeting the biological processes that control appetite and hunger. Some also affect your metabolism.

Medical practitioners often prescribe weight loss medication to people who are still not losing weight despite making healthy lifestyle changes such as going on a healthy diet and exercising.

Most modern weight loss injections belong to a class of drugs called GLP-1 receptor agonists. GLP-1 is a naturally occurring hormone in your body that:

• Regulates appetite by signalling fullness to your brain.
• Slows down how quickly food leaves your stomach.
• Helps stabilise blood sugar levels

These effects mean you feel fuller for longer. As a result, you'll eat less and experience fewer cravings. Some newer medications, like tirzepatide (Mounjaro), also target additional hormones, making them even more effective.

How Do Weight Loss Injections Work?

These medications act on areas of the brain that control hunger. They increase feelings of fullness and reduce appetite, meaning that you'll naturally eat smaller portions and feel satisfied after meals. Your urge to snack will also become weaker.

GLP-1 weight loss medications also improve how your body manages blood sugar. They stimulate insulin release when needed and reduce blood sugar spikes after eating.

The medications help prevent energy crashes that lead to cravings. It is particularly useful if you have insulin resistance or type 2 diabetes.

Which is the Best Weight Loss Injection? Comparison of Top 3 Options in the UK

There are three weight-loss injections people use in the UK: Mounjaro, Wegovy, and Saxenda. The best one depends on factors such as how much weight you lose and the overall experience of your weight loss journey. Here's a closer look at these three medications:

Mounjaro (Tirzepatide)

Mounjaro is an effective weight-loss injection containing the active ingredient tirzepatide. It works on two hormones, GLP-1 and GIP, causing greater appetite suppression. SURMOUNT-1 Clinical trials show up to 22% weight loss with this drug.

Mounjaro requires once-weekly administration. It can help manage type 2 diabetes by improving insulin sensitivity. Other benefits of Mounjaro include:

• Blood sugar control
• Rapid weight loss
• Reduces liver fat content
• Lower systolic blood pressure
• Improves lipid profiles
• Treats obstructive sleep apnoea (OSA)

This injection is most suitable for adults with a BMI (body mass index) of 30 or above, or 27 and above with a weight-related condition.

It's unsuitable for people with a history of Medullary Thyroid Carcinoma (MTC) in their family, or Multiple Endocrine Neoplasia syndrome type 2. It's also unsuitable for people with severe allergies to tirzepatide or any of the ingredients in Mounjaro.

This is the most expensive weight-loss treatment because it's regarded as the most effective injection for body weight reduction.

Wegovy (Semaglutide)

Wegovy is widely used and recommended in the UK as a once-weekly subcutaneous injection with the active ingredient semaglutide. It targets GLP-1 only, and according to the STEP 1 Trials, it showed about 15% body weight loss. It's also worth noting that STEP 5 trials have shown healthy weight loss of about 20% at two years of Semaglutide/ Wegovy use.

Wegovy is also licensed to lower the risk of heart diseases such as heart attacks and stroke. It offers benefits such as:

• Maintaining weight loss for up to two years when combined with lifestyle changes.
• Improving blood sugar control and insulin sensitivity.
• Meaningful reduction in the severity of OSA.

Adults with a BMI of 30+ or a BMI of 27+ and a weight-related condition like high blood pressure or type 2 diabetes are the best candidates for Wegovy. It's also an ideal treatment for adults with a lower BMI who are switching from another GLP-1 medication.

You can't use Wegovy if you have MTC, Multiple Endocrine Neoplasia syndrome type 2, and severe hypersensitivity to semaglutide.

As for cost, Wegovy is cheaper than Mounjaro and offers a balanced price-to-results ratio.

Saxenda (Liraglutide)

Saxenda is a daily injection with the active ingredient liraglutide. This injection curbs appetite and promotes a sense of fullness, so you eat less food.

It can lead to weight loss when you combine it with increased physical activity and a healthy diet. Saxenda clinical studies have shown five to 10% weight reduction.

Some of the benefits of this weight loss injection are:

• Improved metabolic health.
• Better blood sugar levels.
• Helps maintain weight loss for up to three years when used consistently.
• May reduce weight-related issues such as high blood pressure and cardiovascular disease.

The ideal candidate for Saxenda is an adult or adolescent (12+) with a BMI of 30 or greater (or 27+ with a weight-related health condition).

People with MTC and Multiple Endocrine Neoplasia syndrome type 2 (MEN 2) should avoid using Saxenda. It's also unsuitable for people allergic to liraglutide and pregnant women.

Saxenda is usually the cheapest injection at the entry point. However, once you reach the full dose, you'll need about 5 pens per month, which drives up the cost and makes it more expensive than Mounjaro and Wegovy.

A comparison table of three UK-approved weight loss injections.

What is the Best Weight Loss Injection for You?

The best option depends on your personal preferences as follows:

Weight Loss Goals

If you want significant weight loss, consider newer medications. Mounjaro delivers great weight loss for most people.

However, note that it may not be visible at the lower doses or if you're just starting treatment. When your body adjusts, and your dose is gradually increased, you should start losing weight.

Because not everyone is suitable for Tirzepatide use, Wegovy is the next best option.

Medical History

Some of these medications are not suitable for use due to certain medical conditions. Also, you may be taking pills that can interact negatively with the injections.

It's also important to note that weight loss injections are only approved for people who meet the requirements.

Because of these reasons, you should only take weight loss injections under medical supervision. Your healthcare professional will consider your BMI, existing health conditions (e.g., diabetes, high blood pressure), current medications, and risk factors.

Some weight-loss drugs may be more suitable for you depending on your profile. For example, if you're allergic to tirzepatide, Wegovy, and Saxenda may be the better options for you.

Lifestyle

Convenience is also important when choosing a weight-loss injection. Some people can keep up with the daily dosing schedule for Saxenda.

Others cannot and would be better suited to Mounjaro or Wegovy, as they're weekly injections. It's always advisable to choose a weight-management injection that fits your schedule.

Curely Online Pharmacy: Get Weight Loss Injections in the UK Safely

Curely offers a safe, convenient way to access these treatments. With our services, you can complete a quick online consultation and be assessed by a qualified healthcare professional to determine eligibility. Once the practitioner approves use, you'll receive UK-licensed treatment delivered discreetly to your door.

No GP appointments or pharmacy visits. We handle everything online, saving you time while adhering to clinical safety requirements.

And if injections are not the ideal treatment for you, we offer weight-loss pills. Wondering 'What is the strongest weight loss prescription pill?' Explore our oral options today.

FAQs

What is the Most Effective Weight Loss Injection in the UK?

Mounjaro (tirzepatide) is considered the most effective weight-loss injection available in the UK, with studies showing up to 20–22% body weight loss.

Which is Better, Mounjaro or Wegovy in the UK?

Mounjaro often leads to greater weight loss due to its dual-hormone action. But Wegovy remains highly effective, with STEP 5 trials showing about 20% weight loss at two years of use.

Can You Regain Weight After Stopping Mounjaro?

Yes, you can regain weight if you don't maintain lifestyle changes such as eating a balanced diet, staying consistent with your health, practicing mindful eating, and exercising regularly.

What is the Strongest Weight Loss Injection?

Mounjaro is currently the strongest approved weight loss injection in the UK. It is suitable for most people, and you can use it if you're not at high risk of MTC and other conditions.

What are the Long-Term Side Effects of Mounjaro?

According to a NICE (National Institute for Health and Care Excellence) discussion aid, the long-term effects of Mounjaro on health and nutrition are still under discussion.

Conclusion: What is the Best Injection for Weight Loss?

The best injection depends on your needs. Mounjaro offers the strongest results while Wegovy provides a well-balanced, clinically supported alternative. Saxenda is also a suitable choice if you can keep up with the daily schedule.

Weight-loss injections can help you achieve sustainable results under the guidance of a qualified healthcare team. Curely is a specialist weight management service that can guide you through the process safely and confidently. Get started today.

Reference List

• Garvey, W. Timothy, et al. “Two-Year Effects of Semaglutide in Adults with Overweight or Obesity: The STEP 5 Trial.” Nature Medicine, vol. 28, no. 10, 1 Oct. 2022, pp. 2083–2091.
• Jackson, Sarah E., et al. “Prevalence of Use and Interest in Using Glucagon-like Peptide-1 Receptor Agonists for Weight Loss: A Population Study in Great Britain.” BMC Medicine, vol. 24, no. 1, 8 Jan. 2026.
• Jastreboff, Ania M., et al. “Tirzepatide Once Weekly for the Treatment of Obesity.” New England Journal of Medicine, vol. 387, no. 3, 4 June 2022, pp. 205–216.
• NICE. “Overview | Tirzepatide for Managing Overweight and Obesity | Guidance | NICE.” NICE, 23 Dec. 2024.
• Pi-Sunyer, Xavier, et al. “A Randomized, Controlled Trial of 3.0 Mg of Liraglutide in Weight Management.” New England Journal of Medicine, vol. 373, no. 1, 2 July 2015, pp. 11–22.
• Wilding, John P. H., et al. “Once-Weekly Semaglutide in Adults with Overweight or Obesity.” The New England Journal of Medicine, vol. 384, no. 11, 10 Feb. 2021, pp. 989–1002. PubMed.