Struggling to lose weight despite your best efforts? You’re not alone. For many people, weight management isn’t just about willpower or gym sessions. Hormones, appetite signals, medical conditions, emotional health, and lifestyle all play a role.
When diet and exercise alone aren’t enough, two main medical options are often considered: weight loss injections and weight loss surgery. Both can be effective, but both suit different types of patients.
Here’s what you need to know to decide which route may be right for you.
What are weight loss injections?
Weight loss injections are prescription medicines designed to support long-term weight management. In the UK, the two licensed injections for obesity treatment are Wegovy and Mounjaro.
These medications don’t “burn fat” directly. Instead, they work by regulating feelings of fullness, helping you naturally reduce calorie intake and gradually lose weight. You still need to eat a healthy diet and exercise regularly to get the most out of your treatment.
Some key points to know about weight loss injections include:
They are taken once weekly
They support steady, meaningful weight loss
They are intended for long-term use alongside lifestyle changes
They require a consultation before prescribing
Unlike supplements or over-the-counter products, these treatments target the biological systems involved in hunger regulation.
How do weight loss injections work?
Both Wegovy and Mounjaro work by mimicking hormones that are involved in regulating appetite:
Wegovy (semaglutide) mimics GLP-1, a hormone released after eating that signals fullness to the brain and slows gastric emptying.
Mounjaro (tirzepatide) mimics both GLP-1 and GIP, which together help regulate appetite, blood sugar levels, and feelings of hunger.
By enhancing these natural pathways, the injections help:
Reduce hunger
Increase feelings of fullness
Decrease food cravings
Help you feel satisfied with smaller portions
You still need to make lifestyle changes, but many people find that the constant “food noise” becomes much quieter, making those changes easier to maintain. Ultimately, this leads to a reduced calorie intake and weight loss.
How much weight can I lose?
Clinical trials show meaningful results with weight loss injections when used as prescribed. Over a period of 72 weeks for Wegovy and 68 weeks for Mounjaro, the average weight loss at the highest doses was:
19-21% body weight reduction for people taking Wegovy (7.2mg) (1)
22.5% body weight reduction for people taking Mounjaro (15mg) (2)
These outcomes are significant, but there are a few things to remember:
These figures are averages from clinical studies, not real-world guarantees. Everyone responds to treatment differently, and individual outcomes vary.
This weight loss was achieved at the highest available doses, but the highest dose might not be the best option for you. Finding the right dose means balancing side effects with meaningful weight loss, even if that means losing weight at a lower rate.
These outcomes were achieved over 72 weeks. Weight loss injections are not quick fixes. They’re designed for long-term management, and stopping may cause weight regain.
Study participants have to follow diet and exercise plans, alongside taking the medication. To maintain results and support weight loss, you will need to stick to a calorie deficit, regular exercise, and an active lifestyle.
Are weight loss injections safe?
For most eligible patients, Wegovy and Mounjaro are safe when prescribed appropriately. However, they are not suitable for everyone. You should not use these medicines if you:
Have a personal or family history of medullary thyroid carcinoma (MTC)
Have Multiple Endocrine Neoplasia syndrome type 2 (MEN2)
Have certain severe gastrointestinal conditions
Your prescriber will assess your full medical history before approving treatment.
Importantly, being “safe” is not the same as being side-effect-free. In severe cases, patients may experience allergic reactions or gallbladder issues, but these are rare. Much more common are side effects like nausea, diarrhoea, and fatigue. These improve as your body adjusts to your current dose.
Can you get weight loss injections on the NHS?
Yes, you can get weight loss injections on the NHS, but they aren’t available to everyone. Eligibility is restricted, with those living with the most severe health complications due to weight being prioritised. And even if you qualify for weight loss injections, you may experience a long wait for medication.
To get Wegovy on the NHS, you must have (3):
A BMI of 35 or greater, or over 30 in certain high-risk populations
At least one weight-related health problem, such as high blood pressure or heart disease.
Your GP cannot prescribe Wegovy. You’ll need to be referred to a specialist NHS weight management service and participate in a structured weight loss programme to be considered. Referred patients with lower BMIs may also be considered, depending on ethnicity.
The NHS criteria for Mounjaro are even stricter. You must have (3):
A BMI of 40 or more (or 37.5 or more for certain ethnicities)
At least four of the following five weight-related health conditions:
Type 2 diabetes
High blood pressure
Heart disease
Abnormal blood fats
Obstructive sleep apnoea
Mounjaro can be prescribed by a specialist weight management clinic, but, unlike Wegovy, it can also be prescribed by GPs. Not all GPs are offering Mounjaro prescriptions, and NICE guidelines suggest it could take up to 12 years to make medicines like Mounjaro available to everyone who could be eligible (4). Check with your Integrated Care Board (ICB) to see if it’s being offered in your area.
For people who don’t meet NHS criteria or don’t want to wait, private treatment is always an option.
What is weight loss surgery?
Weight loss surgery (also known as bariatric surgery) is an umbrella term for several surgical procedures that help you lose weight. It involves physically altering the digestive system to reduce food intake or nutrient absorption.
Unlike weight management injections, surgery is invasive and permanent (in most cases), but can lead to substantial long-term weight reduction.
What types of weight loss surgery are there?
There are various types of weight loss surgery. The most common include:
Gastric Sleeve – Removes part of the stomach to create a smaller, tube-shaped stomach
Gastric Bypass – Creates a small stomach pouch and reroutes part of the small intestine
Gastric Band – Places an adjustable band around the stomach (less common now)
Gastric Balloon – Places an inflated balloon inside the stomach to take up space
Each comes with a different risk profile. The gastric sleeve is often considered one of the safest options as it has fewer complications compared to other procedures, but it is irreversible, as part of the stomach is removed. Other surgical procedures, like the gastric band and balloon, may be reversed with a follow-up procedure.
Recovery times also vary, but in general, you can expect to leave the hospital within three days following the procedure and reach full recovery in 4 to 6 weeks (5).
Can you get weight loss surgery on the NHS?
You can get weight loss surgery on the NHS, but the eligibility criteria are strict. It’s only typically available to people who (6):
Have a BMI of 40 or more
Have attempted other weight loss methods (diet, exercise, and medicine) without success
Can commit to long-term follow-up care and lifestyle changes after surgery
As with weight loss injections, waiting lists for bariatric surgery can be lengthy. Psychological and medical assessments are also needed before the operation to make sure that it’s the best option for you to successfully manage your weight.
If you don’t qualify for weight loss surgery on the NHS, you can get it done privately.
Comparing weight loss injections and surgery
How are they similar?
Both weight loss injections and weight loss surgery are recognised medical treatments for obesity. They are not cosmetic solutions, but rather are designed to:
Improve long-term health outcomes
Reduce obesity-related complications
Support sustainable weight reduction
Work alongside lifestyle and behavioural change
Both require commitment, neither is a “quick fix,” and both involve medical supervision.
What are the differences?
Despite the similarities, there are many differences in how they work, who they’re designed for, and the level of intervention involved, all summarised below:
Weight Loss | Surgery | |
|---|---|---|
Type of Treatment: | Prescription medication available from an NHS GP or specialist weight management clinic | Surgical procedure only available on the NHS after referral to a specialist weight management clinic |
How it works: | Regulates appetite hormones to reduce hunger and increase fullness | Physically reduces stomach size to help you feel fuller when eating less |
Invasiveness: | Non-surgical self-injections performed at home Reversibility: Yes — treatment can be stopped (but expect weight regain) | Invasive operation under general anaesthetic in a hospital |
Reversibility: | Yes — treatment can be stopped (but expect weight regain) | Usually permanent (except some procedures like gastric band removal) |
NHS Eligibility Criteria: | BMI ≥35 or ≥40 (depending on which medicine), alongside having weight-related health conditions | BMI ≥40 and evidence of failing to lose weight through diet, exercise, and medication |
Weight Loss Expectations: | 15–20% average body weight reduction with long-term use | Often 25–35%+, depending on procedure |
Speed of Results: | Gradual results that usually become visible after several weeks of continuing treatment and increasing the dose | Often faster weight loss in the initial 3 to 6 months post-surgery, then gradual weight loss for 1-2 years. |
Side effects and risks: | Mainly gastrointestinal symptoms like nausea, constipation, diarrhoea, bloating, and vomiting | Surgical risks, including blood clots, stomach leak, infection, or a blocked gut |
Recovery time: | No recovery period required | Around 4-6 weeks |
Ongoing Commitment: | Weekly injections and medical monitoring | Lifelong dietary changes and follow-up appointments |
What about the cost?
For patients who don’t meet NHS criteria or who want quicker access to weight loss injections or surgery, private treatment is available. But when going private, you have to consider the cost. It’s often a deciding factor when comparing the two.
Weight loss injections typically cost between £150 and £300 per month, depending on dose. This is an ongoing monthly commitment, as you need to keep taking the injections every week for the treatment to work and for the weight to stay off.
Weight loss surgery costs between £4,000 and £15,000+, depending on the clinic location and specific procedure. It requires a higher initial investment but does not involve a recurring medication expense (though you may need to pay for follow-up and aftercare costs).
If taking the private route, it’s important not to let cost be the only deciding factor. Medical suitability is far more important than comparing price tags.
Who is each option suitable for?
While both injections and surgery can be effective ways to help you manage your weight, they’re designed for different levels of medical need.
Who should consider weight loss surgery?
Given the risks involved with weight loss surgery, only individuals who have tried other weight loss avenues should consider this option. Surgery is generally reserved for people with severe obesity or high-risk medical complications. It may be suitable if:
Your BMI is 40 or above, or 35+ with serious obesity-related conditions
You have not achieved sufficient weight loss through other medical treatments
Your weight is significantly impacting your health
You understand and accept the risks of surgery
You are prepared for permanent anatomical changes and lifelong follow-up
Who should consider weight loss injections?
Weight loss injections are an attractive option for individuals who aren't "big enough" for surgery but struggle with chronic weight gain. They are often appropriate for people who feel that appetite control is their biggest barrier, and may be suitable if:
Your BMI is 30 or above, or 27+ with weight-related health risks
You have struggled to lose weight through diet and exercise alone
You want a non-surgical approach with no recovery time
You are comfortable with long-term medication
You prefer gradual, medically supervised weight loss
So, which is right for you?
Choosing between weight loss injections and surgery depends on individual needs, medical history, and financial considerations. Each option offers its own set of advantages, but it is important to keep in mind that both require a commitment to healthy lifestyle changes.
If you’re considering medical weight loss treatment, view our weight loss treatments or start a secure online consultation with one of our prescribers. Our clinical team will assess your eligibility and help you decide whether Wegovy or Mounjaro may be suitable to support your weight loss journey.
Taking the first step doesn’t commit you to treatment. It simply gives you personalised guidance so you can make an informed decision about your health.
👉 Start a consultation to see if weight loss injections are right for you
References
Wharton S, Freitas P, Jøran Hjelmesæth, Kabisch M, Kandler K, Ildiko Lingvay, et al. Once-weekly semaglutide 7·2 mg in adults with obesity (STEP UP): a randomised, controlled, phase 3b trial. The Lancet Diabetes & Endocrinology [Internet]. 2025 Sep 1.
Eli Lilly and Company Lilly’s tirzepatide delivered up to 22.5% weight loss in adults with obesity or overweight in SURMOUNT-1 [Internet]. investor.lilly.com. 2022 Apr 28.
NHS. Treatment - Obesity [Internet]. nhs.uk. 2023.
NICE. NICE describes how weight loss drug tirzepatide will be rolled out [Internet]. NICE website: The National Institute for Health and Care Excellence. NICE; 2024.
NHS. Recovering from weight loss surgery [Internet]. nhs.uk. 2024.
NHS. What is weight loss surgery? [Internet]. nhs.uk. 2024