Best Injection for Weight Loss
JUNCTION PHARMACY · WEIGHT MANAGEMENT
What Is the Best Injection for Weight Loss? A Comprehensive London Guide
Compare your options at a weight loss consultation in Brixton and find a treatment that fits your health and routine.
If you have started looking into medical weight loss, you have probably noticed that the options have multiplied quickly. Mounjaro, Wegovy, daily injections, weekly pens and now tablets all promise results, so it is no surprise that one of the questions we hear most at our weight loss service in London is: what is the best injection for weight loss? The honest answer is that the best treatment is the one that fits your body, your health history, your budget and your lifestyle, and that answer is different for almost everyone who walks through our door.
At Junction Pharmacy in Brixton, our pharmacists support patients from Camberwell, Stockwell, Herne Hill and right across South London who want clear, evidence based advice rather than social media hype. This guide is designed to be your starting point. It explains how each treatment works, how they compare, who tends to do best on which option, how the new weight loss tablets fit in, and what to consider before you start.
Quick Answer
There is no single best injection for weight loss for everyone. In head to head research, Mounjaro (tirzepatide) has produced the greatest average weight loss, while Wegovy (semaglutide) has strong long term evidence and proven heart benefits for some patients. Daily liraglutide and the new Wegovy and Foundayo tablets suit people with different needs. The right choice depends on your BMI, medical history, side effect tolerance, preferences and budget, so a pharmacist consultation is the safest way to decide.
Why There Is No One Size Fits All Weight Loss Injection
Excess weight is extremely common in the UK. According to the Health Survey for England 2022, published by NHS England, 64% of adults in England were living with overweight or obesity, and 29% were living with obesity. With so many people affected, it makes sense that treatment cannot be reduced to a single product.
When our pharmacists help someone decide on a treatment, we look at a range of personal factors, including:
- Your current BMI and how much weight you are aiming to lose
- Existing health conditions, such as type 2 diabetes, high blood pressure, heart disease, sleep apnoea or joint pain
- Any history of pancreatitis, gallbladder problems, severe digestive conditions or eating disorders
- Whether you are pregnant, breastfeeding or planning a pregnancy in the near future
- Your contraception, as some treatments can affect how well the oral pill works
- How you feel about needles and whether a weekly, daily or tablet routine suits you better
- Your budget, since private costs vary significantly between treatments and doses
- What you have already tried, including previous medicines and how you tolerated them
How Modern Weight Loss Medicines Work
Most of today’s leading weight loss treatments belong to a group of medicines that mimic hormones your gut releases after eating. The main hormone involved is GLP-1 (glucagon-like peptide-1), and if you want a deeper look at the science, our guide to GLP-1 weight loss injections in London explains the drug class in detail.
In simple terms, these medicines help by:
- Signalling to the brain that you are full, so you feel satisfied with smaller portions
- Slowing the rate at which food leaves the stomach, which helps fullness last longer
- Quietening “food noise”, the persistent thoughts about eating that many patients describe
- Helping the body manage blood sugar more effectively after meals
Mounjaro goes one step further by acting on a second hormone receptor called GIP (glucose-dependent insulinotropic polypeptide) as well as GLP-1. This dual action is thought to be one reason it produced greater average weight loss in clinical trials.
Many people are surprised to learn that several of these medicines were first developed for type 2 diabetes. That history is actually reassuring, because it means there is a long track record of use. Our article on diabetes medicine and weight loss explains why some products are licensed for diabetes, others for weight management, and why that distinction matters.
Your Main Treatment Options Explained
Mounjaro (Tirzepatide)
Mounjaro is a once weekly injection licensed in the UK for both type 2 diabetes and weight management. Treatment usually starts at 2.5 mg and increases in steps every four weeks, up to a maximum of 15 mg depending on response and tolerability.
- In the SURMOUNT-1 trial, people on the highest dose lost an average of around 20.9% of their body weight over 72 weeks
- It is often chosen by people who want the greatest average weight loss
- It can reduce the effectiveness of the oral contraceptive pill, so extra precautions are needed at the start of treatment and after each dose increase
- It is not licensed for under 18s
If you are leaning towards this option, our guide to Mounjaro for weight loss covers dosing, side effects and how to optimise your results.
Wegovy (Semaglutide)
Wegovy is a once weekly semaglutide injection licensed specifically for weight management. The dose usually builds over around 16 weeks to a maintenance dose of 2.4 mg.
- In the STEP 1 trial, participants lost an average of 14.9% of their body weight over 68 weeks
- It has evidence showing reduced risk of major cardiovascular events in adults with established heart disease and excess weight
- It is licensed for adolescents aged 12 and over in specialist settings, as well as adults
- It has one of the longest track records of any modern weight loss medicine
You can find out more about how treatment works, including our pharmacist-led support, in our guide to the first 30 days on Wegovy weight loss injections.
Liraglutide (Saxenda and Equivalent Products)
Liraglutide is an older GLP-1 medicine given as a daily injection. Average weight loss is lower than with weekly options, at around 8% in its main trial, but it can still be a useful choice for some people.
- Its shorter action means side effects may settle more quickly if a dose is stopped
- Lower cost versions have become available in the UK, which may suit tighter budgets
- Daily injections suit people who prefer a fixed everyday routine
Ozempic (Semaglutide for Diabetes)
Ozempic contains the same active ingredient as Wegovy, but it is licensed in the UK only for type 2 diabetes, not for weight management, and is more commonly prescriber through the NHS. UK regulators and professional bodies have advised that it should be prescribed for its licensed use, partly to protect supply for people with diabetes who depend on it. If you have type 2 diabetes, your GP or diabetes team may prescribe it, and weight loss can be a welcome side benefit. Our guide to Ozempic on the NHS explains who can get it and why it is not used as a private weight loss treatment.
Non-Injection Options
Injections are not the only route. Orlistat is a capsule taken with meals that reduces the amount of fat your body absorbs from food. Results are more modest than with GLP-1 medicines, and it works best alongside a lower fat diet.
Weight Loss Treatments at a Glance
The table below gives a simplified overview. Trial results are averages, and your own results may be higher or lower.
| Treatment | How It Is Taken | Licensed For Weight Loss? | Average Trial Weight Loss |
|---|---|---|---|
| Mounjaro (tirzepatide) | Weekly injection | Yes | Around 15% to 21% depending on dose |
| Wegovy (semaglutide) | Weekly injection | Yes | Around 15% |
| Liraglutide (Saxenda and equivalents) | Daily injection | Yes | Around 8% |
| Wegovy tablet (oral semaglutide) | Daily tablet | Yes (UK authorised June 2026) | Broadly comparable to weekly semaglutide injections |
| Foundayo (orforglipron) | Daily tablet | Yes (UK authorised August 2026) | Somewhat lower than leading weekly injections |
| Ozempic (semaglutide) | Weekly injection | No, type 2 diabetes only | Not prescribed for weight loss alone |
| Orlistat (Xenical) | Capsule with meals | Yes | Modest, typically a few percent |
Which Option Might Suit You Best?
This is where personal guidance really matters. Below are some common situations we see in our Brixton consultation room, with the treatments that often come up in each case. These are starting points for discussion, not a prescription.
If You Want the Greatest Average Weight Loss
In the SURMOUNT-5 head to head trial, published in the New England Journal of Medicine, people taking tirzepatide lost an average of 20.2% of their body weight compared with 13.7% for semaglutide over 72 weeks. For many people with a higher BMI, Mounjaro is therefore the first option we discuss. Our detailed Mounjaro vs Wegovy comparison looks at the differences in more depth, including cost and side effects.
If You Have Heart Disease or High Cardiovascular Risk
Wegovy has specific trial evidence showing a reduction in heart attacks, strokes and cardiovascular deaths in adults with established cardiovascular disease and excess weight. If heart health is your main concern, this evidence may make it the preferred choice, even if average weight loss is slightly lower.
If You Really Dislike Needles
The new Wegovy tablet and Foundayo give needle-averse patients a genuine GLP-1 option for the first time. Weekly injections are also worth a second look, as the needles are very fine and many patients tell us the reality is far easier than they expected.
If You Have Type 2 Diabetes
Your diabetes team should always be involved, as weight loss medicines can interact with insulin and sulfonylureas and increase the risk of low blood sugar. Mounjaro and several semaglutide products are licensed for diabetes, so your GP may be able to offer treatment through the NHS.
If Budget Is Your Main Concern
Costs differ by medicine and dose, and higher doses usually cost more. Liraglutide may be a lower cost private option, and it is worth checking whether you qualify for NHS treatment before committing to private care.
If You Are Planning a Pregnancy
GLP-1 medicines should not be used during pregnancy. Wegovy should be stopped at least two months before a planned pregnancy, and Mounjaro at least one month before. If a family is on the horizon, timing matters, so talk to us before starting.
Work Out Your Starting Point
Before your consultation, it helps to have a clear picture of where you are now. Use our calculator below to check your BMI and see a realistic estimate of what weight loss might look like for you. Bring your results along to your appointment so we can make the most of your time together.
Private or NHS: Understanding Your Routes to Treatment
Both NHS and private routes exist, but they have different eligibility criteria, waiting times and levels of choice. If you would like to explore the NHS pathway, our guide to NHS weight management in London explains referral routes in detail, and our article on anti-obesity medication in Brixton takes a broader look at how these medicines fit into obesity care.
On the NHS, access is currently targeted at people with the highest clinical need.
Mounjaro is being introduced in phases through GPs, starting with people with a BMI of 40 or above who also have at least four of five specific weight-related conditions, in line with NICE guidance TA1026
Wegovy is mainly available through specialist weight management services, usually for up to two years, under NICE guidance TA875
Lower BMI thresholds may apply for people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean backgrounds, who face higher health risks at lower BMIs
Privately, Mounjaro and Wegovy can be prescribed to adults with a BMI of 30 or above, or 27 or above with at least one weight-related condition, following a full clinical assessment.
| Consideration | NHS Route | Private Pharmacy Route |
|---|---|---|
| Eligibility | Stricter, based on BMI and several health conditions | BMI 30+, or 27+ with a weight-related condition |
| Waiting time | Can be lengthy due to phased rollout and referral queues | Usually days rather than months |
| Cost | Standard prescription charges where applicable | Paid privately, varies by medicine and dose |
| Choice of medicine | Determined by local pathways | Discussed with your pharmacist based on suitability |
| Ongoing support | Linked to wraparound programmes and GP review | Regular pharmacist check-ins and dose reviews |
Side Effects and Safety: What You Should Know
All weight loss medicines can cause side effects, and knowing what to expect helps you stay on track safely. The most common effects tend to appear when starting treatment or after a dose increase:
- Nausea, which often eases after the first few weeks
- Diarrhoea, constipation or indigestion
- Bloating, burping or stomach discomfort
- Tiredness or headaches, sometimes linked to eating and drinking less
Less common but more serious side effects need prompt attention. Seek urgent medical advice if you experience:
- Severe, persistent stomach pain that may spread to your back, which can be a sign of pancreatitis
- Pain in the upper right of your abdomen, fever or yellowing of the skin or eyes, which may indicate gallbladder problems
- Ongoing vomiting or diarrhoea that leaves you unable to keep fluids down, as dehydration can affect your kidneys
- Signs of a serious allergic reaction, such as swelling of the face or difficulty breathing
A few further safety points are especially important. If you use the oral contraceptive pill and start Mounjaro, the MHRA advises using a non-oral method or adding a barrier method such as condoms for four weeks after starting and for four weeks after each dose increase.
Buying Safely: Why Where You Get Treatment Matters
Demand for weight loss medicines has led to a surge in fake and unlicensed products sold online and through social media. These can contain the wrong dose, the wrong ingredient or harmful contaminants. If you are researching how to buy weight loss injections online safely, make sure your provider:
- Is registered with the General Pharmaceutical Council (GPhC), which you can check on the public register
- Carries out a genuine clinical assessment, including checks on your weight and medical history
- Supplies branded, licensed products in sealed packaging with a patient information leaflet
- Offers follow-up support and a named point of contact if you have questions
- Never sells “research peptides”, unbranded vials or products labelled “not for human use”
- Many patients prefer the reassurance of face to face care. If that sounds like you, our guide to finding a weight loss clinic near me explains what a quality local service should offer, from in-person weigh-ins to help with injection technique.
Getting the Best Results from Your Treatment
Medicine is a powerful tool, but it works best as part of a wider plan. The patients who see the strongest long term results tend to build healthy habits while their appetite is reduced.
- Prioritise protein: eating enough protein at each meal helps protect muscle as you lose weight
- Add strength training: two or more sessions a week of resistance exercise supports muscle, bone health and metabolism
- Eat smaller, slower meals: this reduces nausea and helps you notice fullness signals
- Stay hydrated: reduced appetite often means reduced fluid intake too, which can worsen constipation and fatigue
- Plan for the long term: studies show many people regain a significant amount of weight after stopping treatment, so it is worth discussing a maintenance plan early
The NHS guide to eating a balanced diet is a helpful foundation alongside any treatment plan.
What Happens at Your Consultation in Brixton?
We keep the process simple and supportive, whether you are local to Brixton, travelling in from Camberwell or elsewhere in London. A typical first appointment includes:
- A private conversation about your goals, history and any previous attempts at weight loss
- Measurement of your height, weight and BMI, plus blood pressure where appropriate
- A review of your current medicines, health conditions and contraception
- A clear explanation of the options that suit you, including expected results, side effects and costs
- A demonstration of how to use your pen or take your tablets correctly if treatment is prescribed
- A plan for follow-up reviews as your dose is adjusted
Your Questions Answered
How Quickly Will I Notice a Difference?
Most people notice a change in appetite within the first one to two weeks, often before the scales move much. Weight loss in the first month is usually gradual because you start on a low dose designed to help your body adjust. Results tend to build steadily as the dose increases, with many people seeing their most noticeable progress between months three and nine. Weight loss usually slows and then levels off after around a year to eighteen months, which is a normal part of treatment rather than a sign that it has stopped working.
Can I Switch from One Weight Loss Medicine to Another?
Yes, switching is possible, but it should always be managed by a prescriber. Doses are not directly interchangeable between medicines, so you may need to start the new treatment at a specific dose rather than jumping straight to a high one. You should never take two GLP-1 medicines at the same time. People switch for many reasons, including side effects, a plateau in progress, cost or a preference for a tablet, and your pharmacist can advise on timing and the safest starting point.
What Should I Do If I Miss a Dose?
The advice depends on the medicine. For Wegovy injections, you can usually take a missed dose if it is within five days of when it was due; otherwise skip it and carry on as normal. For Mounjaro, the window is four days. Never take two doses close together to catch up. If you miss more than two weeks of treatment, speak to your pharmacist before restarting, as you may need to return to a lower dose to avoid strong side effects. Always check the patient information leaflet for your specific product.
Can I Drink Alcohol While on Treatment?
There is no strict ban, but moderation is important. Many patients find their tolerance for alcohol drops, and drinking can make nausea and stomach upset worse. Heavy drinking also raises the risk of pancreatitis, which is already a rare concern with these medicines. If you have diabetes and take insulin or certain tablets, alcohol can increase the risk of low blood sugar. Alcohol is also high in calories, so cutting back can support your progress.
How Should I Store My Pens, and Can I Travel with Them?
Unused pens should generally be kept in the fridge between 2°C and 8°C and must never be frozen. Most products can be kept at room temperature for a limited period, so check your leaflet for the exact time and temperature limits. When flying, carry your pens in your hand luggage, as the hold can get very cold. A copy of your prescription or a letter from your pharmacy can help at security.
Will I Lose Muscle as Well as Fat?
Some loss of lean tissue happens with any significant weight loss, whether through diet, surgery or medication. The aim is to keep it to a minimum. Eating enough protein, staying active and including resistance exercise such as weights, bands or bodyweight movements all help protect muscle. We review this at your follow-up appointments.
Do I Need Blood Tests Before Starting?
Not everyone needs blood tests before starting private treatment, but they may be recommended depending on your history. For example, if you have symptoms that suggest undiagnosed diabetes, kidney concerns or a thyroid condition, your pharmacist may suggest a check or ask for information from your GP. With your consent, we may also share details of your treatment with your GP so your medical record stays accurate and joined up.
Can These Medicines Affect My Other Prescriptions?
They can. Because GLP-1 medicines slow stomach emptying, they may change how some tablets are absorbed. People taking warfarin may need closer monitoring, and anyone on insulin or sulfonylureas may need dose adjustments to avoid low blood sugar. The Wegovy tablet also has specific rules about taking other medicines, including levothyroxine, around the time of your dose. Always share a full list of everything you take, including supplements and over the counter products.
Do I Need to Tell Anyone If I Am Having Surgery?
Yes. If you are due to have an operation, a procedure under sedation or an anaesthetic, tell the team caring for you that you are taking a GLP-1 or dual GIP/GLP-1 medicine. Because these medicines slow digestion, food can remain in the stomach for longer, which may increase the risk of inhaling stomach contents during anaesthesia. The team may give you specific fasting instructions, so do not stop your medicine without advice.
Can Teenagers Use Weight Loss Injections?
Wegovy and liraglutide are licensed for some adolescents aged 12 and over, but treatment for young people is managed by specialist NHS services with paediatric expertise. Mounjaro is licensed for adults only. Private pharmacy weight loss services, including ours, are for adults aged 18 and over. If you are worried about a young person’s weight, the best first step is to speak with their GP, who can arrange appropriate support.
Finding the Right Fit for You
So, what is the best injection for weight loss? For many people, Mounjaro offers the greatest average results. For others, Wegovy’s heart benefits, a lower cost daily option, or one of the new tablets will be a better match. The most important step is not picking a brand from a headline, but having an honest conversation with a qualified professional who understands your health and your goals.
Whether you live in Brixton, Camberwell or anywhere else in London, our pharmacists are here to guide you through every stage, from your first consultation to your long term maintenance plan.
Speak to a Pharmacist About Your Options
Not sure where to start? Our Brixton team will assess your suitability, explain each treatment in plain language and help you choose a plan you can stick with. Book online or get in touch for a friendly, confidential chat.
Call us on 02072747599 or email junctionpharmacy@gmail.com
Disclaimer: This article is for general information and guidance only and does not replace personalised medical advice. Weight loss medicines are prescription-only and are not suitable for everyone. Always speak to a pharmacist, GP or other qualified healthcare professional before starting, changing or stopping any treatment, and read the patient information leaflet supplied with your medicine.
☑ Clinically Reviewed by Pharmacy Mentor
A pharmacist reviews the content to help ensure medicines are presented responsibly and that patient-facing health information is accurate, appropriate, and aligned with current clinical guidance.
Last reviewed: October 2026
Written on behalf of Junction Clinics by Pharmacy Mentor.
Created: 11 March 2025. Last formatting review: 6 October 2026.
