GLP-1 Weight Loss Injections: Benefits, Comparisons and Side Effects

Everything you need to know about Wegovy, Mounjaro and Saxenda and how the new Wegovy pill compares

If you've been exploring your options for weight loss, you've probably come across GLP-1 treatments the injectable medications that have changed how clinicians approach obesity management. Drugs like Mounjaro and Wegovy have become household names, but knowing which one suits your situation, and whether injections are even the right route for you, can feel overwhelming.

This guide cuts through the noise. Here's what you actually need to know.

What Are GLP-1 Weight Loss Injections?

GLP-1 stands for glucagon-like peptide-1 a natural hormone your body releases after eating. It plays a key role in regulating blood sugar, stimulating insulin production, and signalling to your brain that you're full.

GLP-1 receptor agonists are medicines that mimic this hormone. Here's what they do:

• Bind to GLP-1 receptors in the gut and brain, triggering insulin release and reducing blood glucose
• Slow down how quickly your stomach empties, so you feel fuller for longer
• Reduce hunger signals in the brain, making it easier to eat less without constant willpower
• In some cases, lower blood pressure and improve cholesterol levels, reducing cardiovascular risk

The most widely used GLP-1 weight loss injections currently available in the UK are semaglutide (Wegovy), tirzepatide (Mounjaro), and liraglutide (Saxenda).

How Do You Take Them?

All three are self-administered injections, delivered subcutaneously meaning just under the skin into the abdomen, upper arm, or thigh. The technique is straightforward and most patients are comfortable with it within the first week.

• Wegovy (semaglutide): Once weekly injection
• Mounjaro (tirzepatide): Once weekly injection
• Saxenda (liraglutide): Once daily injection

Like all prescription weight loss treatments, these medications work best as part of a structured programme - not as a standalone solution. Pairing them with a reduced-calorie diet, regular physical activity, and clinical support produces significantly better and more lasting results.

At Rightangled, every patient on a GLP-1 programme receives ongoing clinician oversight, regular check-ins, and access to our clinical team throughout their treatment - not just at the point of prescription.

What Are the Benefits?

The headline benefit is clinically significant weight loss, often beyond what diet and exercise alone can achieve for people living with obesity. But the effects go further than the number on the scales:

• Appetite regulation - reduced hunger and fewer cravings, which makes sustaining a calorie deficit more manageable
• Cardiovascular benefits - improvements in blood pressure, cholesterol, and in some cases direct reduction in cardiovascular risk
• Blood sugar control - particularly relevant for patients with pre-diabetes or type 2 diabetes
• Sustained results - unlike many commercial diet programmes, GLP-1 treatments have robust long-term trial data behind them

Consistency is the key variable. Patients who follow their dosing schedule and titration plan consistently get the best outcomes.

Comparing the Options

All three treatments are MHRA-approved for weight management in the UK. Here's how they compare at a glance:

Mounjaro works on two receptors (GLP-1 and GIP), which is why its weight loss figures tend to be higher than semaglutide alone. Saxenda is the oldest of the three and generally considered less potent, though it remains a clinically appropriate option for some patients.

Not sure which is right for you? Our consultation process is designed to match you to the most suitable treatment based on your health history, BMI, and goals - not just what's trending.

Related reading: Wegovy vs Mounjaro: A Full Clinical Comparison

Injections vs Pills - Is There a Difference?

This is increasingly relevant now that oral semaglutide (the Wegovy pill) has received MHRA approval in the UK, making it the first oral GLP-1 licensed for weight management in Europe.

The efficacy is comparable. Clinical trial data shows patients on oral semaglutide lose between 15.1% and 17.4% of their body weight depending on adherence - very similar to the injectable form. The key practical differences:

• The injection is taken once weekly - some patients find this easier to maintain than a daily pill routine
• The pill is taken once daily on an empty stomach, with a strict 30-minute wait before eating or drinking anything else
• The pill requires no refrigeration and no needles - a significant advantage for needle-averse patients and frequent travellers

If you've been putting off GLP-1 treatment because of injections, the oral option removes that barrier entirely.

Learn more: Wegovy Pill UK: Everything You Need to Know

Are They Safe?

Yes - when prescribed and monitored correctly. Wegovy, Mounjaro, and Saxenda are all MHRA-approved, meaning they've met rigorous standards for safety, quality, and effectiveness.

The most important safeguard is clinical oversight. These are prescription-only medications, and your dosing plan should be managed by a licensed clinician who can monitor for side effects, adjust your treatment if needed, and check in on your overall health as you progress.

At Rightangled, our clinical team conducts regular reviews throughout your treatment - this isn't a one-click prescription service.

Side Effects to Know About

Side effects are common, particularly in the early weeks and during dose increases. Most are gastrointestinal and ease as your body adjusts:

• Nausea and vomiting - the most frequently reported; usually manageable with smaller meals and avoiding fatty foods
• Diarrhoea or constipation
• Stomach discomfort - bloating, heartburn, or abdominal pain
• Injection site reactions - mild irritation or redness at the injection site (not relevant for the pill form)

Serious side effects are rare but worth knowing: pancreatitis, gallbladder issues, and thyroid concerns carry boxed warnings on packaging. If you experience severe abdominal pain or notice a lump in your neck, seek medical attention promptly.

Our clinical team is available to answer questions about side effects at any point during your treatment.

Who Is Eligible?

GLP-1 weight loss injections are clinically appropriate if:

• Your BMI is 30 or above (classified as obese), or
• Your BMI is 27-29.9 with at least one weight-related health condition - such as high blood pressure, pre-diabetes, raised cholesterol, or sleep apnoea

They are not suitable if you are pregnant or breastfeeding, or if you have:

• Type 1 diabetes
• Severe kidney or liver disease
• A personal or family history of thyroid cancer or certain genetic conditions (MEN2 syndrome)
• A known allergy to any of the active ingredients

Speak to a clinician before starting if you have a history of pancreatitis, diabetic retinopathy, or serious digestive conditions.

Common questions about GLP-1 injections

What should I do if I miss a weekly dose?

Check the patient leaflet that came with your pen, because the rule differs between medicines. For Mounjaro, you can take a missed dose if 4 days or fewer have passed since your usual day. For Wegovy, the window is 5 days. If more time has passed, skip that dose and inject on your next scheduled day. Never take two doses close together to catch up. If you have missed more than one dose in a row, speak to your clinician before your next injection, as they may want to adjust your dose.

How should I store my injection pens?

Keep unused pens in the fridge, between 2°C and 8°C, in their original box to protect them from light. Do not freeze them, and do not use a pen that has been frozen, even if it has thawed. Once a pen is in use, it can usually be kept at room temperature for a limited time, but how long varies by product, so follow your leaflet. When travelling, carry pens in your hand luggage in a cool bag. Our guide to travelling with weight loss treatment covers this in more detail.

Do these injections affect contraception or pregnancy plans?

They can. Mounjaro may make the contraceptive pill less reliable, so the MHRA advises switching to 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. None of these medicines should be used during pregnancy, and they need to be stopped some time before you try to conceive. If you are planning a pregnancy, or think you might be pregnant, tell your clinician straight away so they can advise you.

How long will I need to stay on weight loss injections?

There is no fixed end date. These medicines are licensed for long-term weight management, and your clinician will review your progress regularly to decide whether continuing is still right for you. Many people find their appetite returns when they stop, and some or all of the weight can come back, especially if eating and activity habits have not changed. If you are thinking of stopping, talk it through with your clinician first so you have a plan for keeping the weight off. Read more about what happens when you stop weight loss medication.

Can weight injections affect my other medicines?

Yes, in some cases. Because they slow how quickly your stomach empties, they can change how some tablets are absorbed. This matters most for medicines where the exact level in your blood is important, such as warfarin. If you take insulin or a sulfonylurea such as gliclazide for diabetes, your risk of low blood sugar goes up, and your diabetes dose may need lowering. Give your clinician a full list of everything you take, including over-the-counter remedies and supplements.

Choosing the Right Treatment for You

The right GLP-1 treatment depends on your health history, lifestyle, and what you're most likely to stick to long term. Mounjaro delivers the highest average weight loss figures. Wegovy (both injectable and oral) is well-established with extensive trial data. Saxenda suits patients for whom a different titration schedule is preferable.

At Rightangled, Medetone our online consultation takes around 5 minutes and is reviewed by a UK-licensed clinician. If you're eligible, your prescription is issued and your treatment plan is set up - with our clinical team available throughout.

Ready to find out which treatment is right for you?

Start your free consultation at Rightangled →

Already in the US and want to start today? Wegovy tablets available now at Medetone from $149 →

This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before starting any prescription medication.

References

1. Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity. NEJM 2022. https://www.nejm.org/doi/full/10.1056/NEJMoa2206038
2. MHRA / NHS. Accessing Wegovy for weight loss. https://healthmedia.blog.gov.uk/2023/09/04/accessing-wegovy-for-weight-loss-everything-you-need-to-know/
3. Pi-Sunyer X et al. A Randomized, Controlled Trial of 3.0 mg of Liraglutide in Weight Management. NEJM / PMC 2015. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5358074/
4. OASIS 1 trial. Oral semaglutide for weight management. ClinicalTrials.gov NCT05035095. https://clinicaltrials.gov/study/NCT05035095