Weight Loss Injections

How do weight loss injections work?

Weight loss injections like belong to a group of medicines called GLP-1 receptor agonists. This means they mimic a natural hormone in your body, called GLP-1, which is released after you eat.

These treatments work by activating GLP‑1 receptors in key areas of the body, including the brain, stomach and pancreas. By doing this, they help you:

• feel fuller sooner when eating
• stay satisfied for longer
• reduce the urge to snack or overeat.

Some treatments, like Mounjaro, go a step further by targeting an additional hormone, GIP, making it a GLP-1/GIP receptor agonist. GIP receptor agonists help the body handle glucose more efficiently and influence your appetite and metabolism, especially when paired with GLP-1 activity.

Can you switch weight loss injections?

In many cases, it’s possible to switch between weight loss injections, but this should always be done under the guidance of a healthcare professional.

Each treatment works slightly differently and is taken on a different dosing schedule, so your prescriber will need to review your progress, any side effects, and your overall response before recommending a change.

Switching may be considered if your current treatment isn’t giving you the results you expected, isn’t well tolerated, or if a more suitable option becomes available.

In any case, your clinician will guide you on how to transition safely, including when to stop one treatment and start another, to help minimise side effects and maintain consistent weight loss support.

What is the best injection for weight loss?

While some may be more effective in clinical trials, there isn’t a single ‘best’ weight loss injection.

The right option depends on your goals, lifestyle and how your body responds to treatment. What works best for one person may not be the best fit for another.

Cost, dosing frequency, availability, and how well you tolerate the treatment can all play a role in deciding which option is right for you.

The table below gives you a quick overview of the main weight loss injections, and how they compare:

Mounjaro

Mounjaro is the newest weight loss injection available in the UK. Licensed to treat weight loss in November 2023, it’s manufactured by Eli Lilly and is the first and only dual-agonist treatment, setting it apart from available treatments.

Mounjaro works by mimicking two different hormones produced in your gut (GLP-1 and GIP), which helps it regulate blood sugar, increase fat metabolism, and suppress appetite.

It’s currently the most effective weight loss injection treatment available in the UK, with clinical trials showing an average weight loss of 22.5% over 72 weeks.

Wegovy

Wegovy contains semaglutide and, like Mounjaro, works by mimicking the GLP-1 hormone. It’s one of the most well-established weight loss injections in the UK and is specifically licensed for weight management.

Recent studies also showed strong evidence of Wegovy being very beneficial for heart health, regardless of how much weight is lost. This led to Wegovy being licensed in the UK to help lower the risk of serious cardiovascular events, including heart attacks and strokes.

With the recent approval of the new 7.2mg maximum dose, Wegovy has closed the gap in effectiveness between itself and Mounjaro, with clinical trials now reporting average weight loss of 21%.

Liraglutide injections (Saxenda, Nevolat, Biolide, Plaobes)

Liraglutide-based injections, including branded options like Saxenda and generic options like Nevolat, Biolide and Plaobes, are GLP‑1 receptor agonists that work by helping you feel full sooner and reducing your appetite throughout the day.

These treatments are typically taken daily rather than weekly and have been used for longer than newer options, giving them a well-established safety profile.

While they are effective for weight loss, they generally offer more moderate results compared to newer injections like Mounjaro or Wegovy.

Are weight loss injections safe?

Weight loss injections are generally considered safe when prescribed and their use monitored by a qualified healthcare professional.

They’re licensed medicines in the UK, meaning they’ve been carefully assessed for safety and effectiveness by regulators like the MHRA (Medicine and Health product Regulatory Agency) before being approved for use.

Weight loss injections aren’t suitable for everyone, and you’ll need a consultation to check your medical history, current medications and overall health before starting treatment. Ongoing support and regular reviews help ensure the treatment remains safe and effective for you.

Who can use weight loss injections?

Many people consider weight loss injections after finding that diet and exercise alone haven’t delivered the results they need. First though, they’ll need to complete an online consultation so their eligibility can be assessed.

At Chemist4U, weight loss injections are prescribed following a clinical assessment. You may be eligible if you have a BMI of 30 or above, or 27 and above with a weight-related condition.

All treatments are approved by UK‑registered prescribers after reviewing your medical history, medications and weight loss goals to ensure they’re safe and suitable for you.

If you’re thinking about starting treatment, it can be helpful to see what results are possible. You can explore real before and after weight loss injection results to understand what to expect and how treatment could work for you.

Can you get weight loss injections on the NHS?

While you can get weight loss injections on the NHS, access is much more restricted than private treatment.

Eligibility is based on NICE (National Institute for Health and Care Excellence) guidance and is usually limited to people with obesity and related health conditions, often through specialist weight management services rather than a standard GP prescription.

Mounjaro

While available on the NHS, is reserved and prioritised for people with the highest clinical need. You’ll have to be referred into a specialist weight management service, and have:

• a BMI of 40 or above
• four or more weight-related health conditions (e.g. type 2 diabetes, high blood pressure, high cholesterol, sleep apnoea, cardiovascular disease)

Wegovy

Wegovy is available through NHS specialist services and has slightly broader eligibility than Mounjaro but is still tightly controlled. It’s prescribed as part of a structured weight management programme, that’s typically accessed through specialist clinics. To be eligible, you’ll need to have:

• a BMI of 35 or above
• at least one weight-related health condition (e.g. type 2 diabetes, high blood pressure, cardiovascular disease, sleep apnoea)

Liraglutide injections (Saxenda, Nevolat, Biolide, Plaobes)

Liraglutide follows NICE eligibility for weight management medicines and sits broadly in line with Wegovy criteria:

• BMI of 35 or above, plus at least one weight-related condition

Weight loss injection prices

While weight loss injections do come with a monthly cost, many people find it helpful to think of this as an ongoing investment in their health and long-term wellbeing.

Saxenda is omitted from the table above as it’s a daily injection, not weekly, and so breaking down the costs is slightly different. Each pen comes with the same amount of treatment, but the amount you use is different each day until you reach the maximum dose. Chemist4U currently sells Saxenda in the following pack sizes:

• 5 pens - £375
• 10 pens - £750

Alternatively, there are generic options that contain the same active ingredient, liraglutide and are much cheaper than Saxenda, like:

• Nevolat: £53.99 for a single pen, £630 for 15 pens
• Biolide: £110.99 for three pens, £199.99 for five pens
• Plaobes: £125 for three pens, £210 for five pens

At first glance it may seem that the cost varies wildly. However, due to the way in which liraglutide injections work, pricing often starts at more than one pen. The exception to this is Nevolat, where you’re able to buy one pen at a time.

Bundles

Chemist4U offers a variety of weight loss injection bundles so you’re able to get the most out of the treatment. They’re both cost effective, and help ensure you’ve always got enough medication in.

Whether it’s bundles that contain increasing doses, or you want two or three months of one dose that works for you, we’ve got you covered.

Where to buy weight loss injections safely

Using a trusted online pharmacy like Chemist4U reduces the risk of counterfeit or unsafe medication as your treatment will always be:

• prescribed by UK-regulated clinicians
• dispensed by a General Pharmaceutical Council (GPhC)-registered pharmacy
• supplied through a secure, regulated supply chain

But your journey with us doesn’t end at checkout. We offer follow-up care, support from our clinicians and expert advice available on our site, designed to help you every step of the way.

Not just this, but we offer free, next day delivery in discreet packaging, so you can get your medication privately, and without any unnecessary hassle.

That’s why thousands of patients have chosen us for their weight loss journey, and why we’re proud to say more than 110,000 customers have given us 5-stars on Trustpilot.

Common weight loss injection side effects

Weight loss injections are generally well tolerated, but like any medicine, they can cause side effects, especially when you first start treatment or increase your dose.

Because of how they work the most common side effects are usually digestive but will usually improve as your body gets used to the treatment. These side effects can include:

• nausea
• vomiting
• diarrhoea
• constipation
• bloating

In most cases, these side effects are mild and temporary, and your prescriber will guide you on how to manage them. If symptoms persist or become severe, it’s important to seek advice from a healthcare professional.

For more information, we’ve got in-depth guides covering Mounjaro side effects, Wegovy side effects, and Saxenda side effects.

3 ways to boost your weight loss on injections

While effective on their own, to get the most out of your injections, it’s good to try and adopt minor lifestyle changes at the same time.

The best bit? You’ve not got to do a lot to get way more out of your treatment.

Change your eating habits

Weight loss injections can help reduce your appetite, but making small changes to your diet can make a big difference to your results.

Focus on balanced meals with plenty of protein, fibre and whole foods, which can help you stay fuller for longer and avoid unnecessary snacking.

Keeping portion sizes consistent and building regular meal patterns also helps you get the most out of your treatment.

Start moving more

You don’t need to follow an intense exercise routine to see results. Small increases in daily movement can support weight loss, like:

• walking more
• taking the stairs
• introducing light exercise into your week

These can all help boost your progress and improve your overall health, making it easier to maintain your results long-term.

Stay consistent

Consistency is key when it comes to weight loss injections. Taking your medication as prescribed and sticking to your routine will help you see steady, sustainable results.

It’s normal for progress to vary week to week, so focusing on long-term habits rather than quick wins will help you stay on track.

Alternatives to weight loss injections

If injections aren’t right for you, there are also weight loss tablets available in the UK. These are prescription treatments that work in different ways, like reducing appetite or limiting how much fat your body absorbs from food.

They can be a good option if you prefer not to inject, or if you’re looking for a more familiar treatment format alongside diet and lifestyle changes.

There are also other oral treatments in development, like Wegovy tablets and Foundayo, which aim to offer similar benefits to injections without the need to inject. These are not currently licensed in the UK and are still under review by the MHRA.

Sources

• Tirzepatide Once Weekly for the Treatment of Obesity. NEJM. [Accessed 21 May 2026]
• Once-weekly semaglutide 7·2 mg in adults with obesity (STEP UP): a randomised, controlled, phase 3b trial. PubMed. [Accessed 21 May 2026]
• A Randomized, Controlled Trial of 3.0 mg of Liraglutide in Weight Management. NEJM. [Accessed 21 May 2026]