GLP-1 Weight Loss Injections: Everything You Need to Know
Deciding whether a GLP-1 weight loss injection is right for you can feel overwhelming, especially with so much conflicting information online. Wegovy and Mounjaro have become two of the most talked about treatments in weight management, but understanding how they actually work, who they are suitable for, and what results are realistic matters far more than headlines.
At Junction Pharmacy, our medical weight loss clinic in London provides fully assessed, clinician-led access to GLP-1 treatments alongside ongoing support. If you are considering starting a programme, our team can talk you through your options.
Short answer: Wegovy and Mounjaro are prescription only GLP-1 injections that work by reducing appetite and slowing digestion, supporting significant weight loss when combined with a reduced calorie diet and regular activity. Most side effects are mild and settle over time, though eligibility depends on a full clinical assessment covering your medical history, current medications and any risk factors. Neither medication is a standalone quick fix, and long-term success relies on the lifestyle changes made alongside treatment, ideally with ongoing clinical support to monitor progress and adjust your plan as needed.
What Are GLP-1 Weight Loss Injections?
GLP-1 receptor agonists are a class of medication originally developed for type 2 diabetes management. They mimic a naturally occurring gut hormone called glucagon-like peptide-1, which plays a role in appetite regulation, insulin release and how quickly food moves through the stomach. Two of the most widely prescribed brands in the UK are Wegovy (semaglutide) and Mounjaro (tirzepatide).
Both medications are administered as a once weekly injection and are licensed for weight management in adults who meet specific clinical criteria. They work by:
➤ Slowing down gastric emptying, which helps you feel fuller for longer
➤ Reducing appetite signals sent to the brain
➤ Improving blood sugar regulation
➤ Supporting a sustainable reduction in overall calorie intake
How Wegovy And Mounjaro Differ
Although both are GLP-1 based treatments, Mounjaro also acts on a second hormone receptor called GIP, which some research suggests may contribute to its slightly higher average weight loss results in clinical trials. Neither medication is inherently “better” for everyone. The right choice depends on your medical history, tolerance to side effects and how your body responds during titration, which is why a proper clinical assessment through our weight loss support service matters before starting either treatment.
How Effective Are GLP-1 Injections?
Clinical trial data has shown substantial average weight loss with both medications when combined with dietary changes and increased activity. According to a UK based study published by the National Institute for Health and Care Research, GLP-1 receptor agonists have been associated with clinically meaningful weight reduction in adults with obesity, alongside improvements in blood pressure and cholesterol markers.
It is worth remembering that results vary considerably between individuals. Factors such as starting weight, adherence to dosing schedules, diet quality and activity levels all influence outcomes.
Comparing Your Options: Injections vs Tablets
| Treatment | How It Works | Common Side Effects | Potential Benefits |
|---|---|---|---|
| Wegovy (semaglutide) | Weekly injection, GLP-1 receptor agonist | Nausea, constipation, fatigue, reflux | Significant average weight loss, cardiovascular benefits noted in trials |
| Mounjaro (tirzepatide) | Weekly injection, dual GLP-1 and GIP agonist | Nausea, diarrhoea, reduced appetite, indigestion | Higher average weight loss in some trials, improved insulin sensitivity |
| Orlistat | Oral capsule, blocks fat absorption in the gut | Oily stools, urgency, flatulence, abdominal discomfort | No injection required, generally modest weight loss support |
Who Can Have GLP-1 Injections?
Eligibility is based on clinical need, not personal preference alone. Generally, GLP-1 treatments are considered appropriate for adults who have:
➤ A BMI of 30 or above, or 27 and above with a weight related health condition
➤ No contraindicated personal or family medical history, such as certain thyroid cancers or pancreatitis
➤ Realistic expectations and a willingness to commit to lifestyle changes alongside treatment
➤ Completed a full clinical assessment with a prescriber
Patients in Brixton and across London often ask whether age affects eligibility. While most treatment is aimed at adults, a prescriber will always assess suitability on an individual basis rather than age alone.
Who Should Avoid GLP-1 Medications?
GLP-1 injections are not suitable for everyone. You may be advised against starting treatment if you:
➤ Are pregnant, breastfeeding, or planning pregnancy in the near future
➤ Have a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2
➤ Have a history of pancreatitis
➤ Have an active eating disorder
➤ Are under 18, unless specifically assessed and approved through a paediatric pathway
A thorough medical history review during your consultation at our clinic ensures any risk factors are identified before treatment begins.
Safety, Side Effects And What To Expect
Most side effects associated with GLP-1 injections are gastrointestinal and tend to reduce over the first few weeks as the body adjusts. These typically include nausea, mild constipation or diarrhoea, and occasional fatigue. Starting on a low dose and increasing gradually, known as titration, is designed specifically to minimise these effects.
➤ Always inject on the same day each week for consistency.
➤ Stay hydrated, particularly if experiencing nausea or reduced appetite.
➤ Eat smaller, more frequent meals rather than large portions during the early weeks.
➤ Report any severe abdominal pain, persistent vomiting or signs of an allergic reaction to your prescribing clinician immediately.
Rare but serious side effects can include pancreatitis and gallbladder problems. This is why ongoing clinical supervision, rather than purchasing medication without prescriber oversight, is so important.
How Do GLP-1 Injections Compare To Orlistat?
Orlistat works in a completely different way to GLP-1 medications. Rather than affecting appetite hormones, it works in the gut to reduce the amount of dietary fat absorbed from food. It has been available in the UK for many years, including in lower strength over the counter forms.
Generally, average weight loss achieved with Orlistat is more modest compared with GLP-1 injections, and it comes with its own tolerability challenges, particularly around digestive side effects if a high fat meal is eaten. For many patients, GLP-1 treatments offer a more consistent and better tolerated route to significant weight loss, though Orlistat may suit those who prefer a tablet based option or who cannot use injectable treatments. Your clinician can help you weigh these options during your initial weight loss consultation.
The First GLP-1 Tablet Approved In The UK
In a significant development for weight management, the UK approved its first GLP-1 tablet form, offering an oral alternative to weekly injections. According to the official government announcement, this tablet based semaglutide product represents a new option for patients who may prefer not to self-inject, while aiming to deliver similar clinical benefits to the injectable form.
This approval marks a meaningful shift in how weight loss treatment may be delivered in the future, potentially widening access for patients who have previously been hesitant about injectable medication. As with all GLP-1 treatments, eligibility and suitability will still be assessed by a prescriber on an individual basis.
Curious whether you would be a suitable candidate? Contact our team to arrange an assessment.
Why Lifestyle Changes Matter Alongside Treatment
No injection, tablet or capsule works in isolation. GLP-1 medications and Orlistat are designed to support a wider weight loss plan, not replace one. Sustainable results tend to come from a combination of factors working together, including:
➤ Balanced nutrition
➤ Regular movement
➤ Good sleep
➤ Stress management
Patients in London who pair their treatment with practical lifestyle adjustments, such as building more protein into meals, walking daily and keeping consistent sleep hours, often find their progress is steadier and easier to maintain once treatment ends. Small, realistic changes made gradually tend to stick far better than drastic overhauls, and your clinical team can help tailor these adjustments around your individual routine, preferences and any existing health conditions.
Curious How Much Weight You Could Lose? Try Our Checker
Wondering what kind of results might be realistic for you before starting treatment? Our handy weight loss checker gives you a quick, personalised estimate based on details like your current weight, height and goals, helping you set realistic expectations from the outset. It only takes a couple of minutes and is a helpful first step before booking a full clinical consultation with our team in London.
Frequently Asked Questions
How much weight can I expect to lose with a GLP-1 injection?
This varies by individual and by medication. Clinical trials have shown average weight loss ranging from around 10 to 20 percent of starting body weight over 12 to 18 months, though results depend heavily on adherence, diet and activity levels alongside treatment.
Do I need to change my diet while taking Wegovy or Mounjaro?
Yes. These medications are licensed to be used alongside a reduced calorie diet and increased physical activity, not as a standalone solution. A balanced eating plan supports better tolerability and more sustainable long-term results.
Will I regain weight if I stop taking a GLP-1 medication?
Some weight regain is common after stopping treatment, particularly if lifestyle changes were not embedded during the programme. This is why our clinics focus on gradual, sustainable habit changes alongside medication rather than treating the injection as a quick fix.
Can I take a GLP-1 injection alongside other medications?
It depends on the medications involved. Some drugs, particularly those affecting blood sugar or absorbed through the gut, may need timing adjustments. Always disclose your full medication history during your consultation so your clinician can check for interactions.
Is Mounjaro stronger than Wegovy?
Mounjaro has shown slightly higher average weight loss results in some head to head trial data, largely attributed to its dual hormone action. However, individual response varies and a clinician can help determine which option suits your specific health profile.
Is the new GLP-1 tablet as effective as the injection?
Early data suggests the oral tablet form can offer comparable benefits, though real world, longer term evidence is still developing following its recent UK approval. Your prescriber can advise on availability and suitability as more data becomes available.
Making An Informed Decision
Choosing whether to start a GLP-1 weight loss injection is a significant decision that deserves proper clinical input, not guesswork based on social media trends. Understanding how the medication works, what side effects to expect and how it fits alongside sustainable lifestyle changes gives you the best chance of long-term success.
At Junction Pharmacy, our team across London supports patients from that very first consultation through to ongoing dose reviews and lifestyle guidance. We believe informed patients make better, safer decisions, and we are here to guide that process every step of the way.
To arrange your consultation, call us on 02072747599, or email junctionpharmacy@gmail.com.
Disclaimer: This article is intended for general guidance and educational purposes only. It does not constitute medical advice and should not replace personalised guidance from your prescribing clinician or pharmacist. Individual suitability, dosing and results vary and any decision about starting, changing or stopping medication should always be discussed with a qualified healthcare professional before being made.
