Weight-loss injections are a type of prescription medication used to support sustainable, healthy weight management. They work by influencing appetite and digestion, helping people eat less while feeling satisfied. This guide explains how they work, who they’re suitable for, and what to expect when starting treatment.
Learn about weight-loss medication and where injectable treatments fit in.
Clinical experts in weight management
NICE and MHRA approved medications
Lifestyle coaching and support included
Written by
Dr Adam Abbs
Doctor
Reviewed by
Medicspot Staff Author
Author
Last Updated:
Next Review: Oct 30, 2026
Weight-loss injections are medications given as weekly self-injections using a pre-filled pen. They are prescribed for people who meet medical criteria for obesity or who have health conditions linked to their weight.
These treatments help regulate appetite and blood sugar, making it easier to maintain a calorie deficit and improve metabolic health. They are always prescribed under medical supervision and work best when combined with nutrition, activity, and behavioural support.
Always discuss any previous medications or medical conditions with your clinician before starting injection therapy. This ensures the right treatment and dose for your situation.
Most modern weight-loss injections act on hormones that regulate hunger and fullness. They mimic the action of GLP-1 (glucagon-like peptide-1) which is a natural hormone that helps control appetite, digestion, and insulin release. This slows the rate at which food leaves the stomach and helps you feel full for longer. Some newer treatments also act on GIP receptors, which may enhance these effects.
Typical results:
Weight-loss injections are not a “quick fix.” They support long-term change when combined with personalised nutrition and movement plans.
There are 3 main types of weight loss injection: GLP-1 receptor agonists (e.g. Semaglutide); Dual agonists (e.g. Tirzepatide); Older injection types (e.g. Liraglutide).
Let’s look at them in turn.
These medicines mimic the GLP-1 hormone to help reduce appetite and regulate blood sugar. They are usually taken once a week.
In studies, people using GLP-1 injections lost on average around 15% of their body weight after a year, with improvements in blood sugar and heart health markers.
In the UK, semaglutide is available under the brand name Wegovy. (Brand names are provided for educational purposes only. Medicspot does not promote any specific prescription-only medicine.)
Common side-effects of GLP-1 receptor agonists include: mild nausea, reflux, constipation, and fatigue – but they are usually temporary.
These newer treatments act on two hormone pathways (GLP-1 and GIP). They may help some people achieve 20–25% body-weight reduction, based on recent clinical trials. Tirzepatide is taken once weekly using a similar injection pen.
In the UK, tirzepatide is available under the brand name Mounjaro. (Brand names are provided for educational purposes only.)
Earlier GLP-1 medications such as liraglutide (Saxenda) require daily injections rather than weekly ones.
While liraglutide is effective, newer options like Wegovy and Mounjaro are now preferred because they last longer in the body and tend to produce greater weight loss.
When used correctly and combined with healthy habits, weight-loss injections can lead to steady, clinically meaningful results.
Typical progress pattern:
Results vary between individuals depending on factors such as dose, diet, activity, and adherence.
Like any medication, weight-loss injections can cause side-effects. Most are mild and short-lived, especially during the first few weeks as your body adjusts.
Common side-effects:
Contact your clinician if side-effects persist or worsen, or if you experience severe abdominal pain or vomiting.
Staying hydrated, eating smaller meals, and avoiding heavy or greasy foods can help minimise side-effects.
Weight-loss injections are usually prescribed for people who:
These medications are not suitable for people who are pregnant, breastfeeding, or have certain medical conditions (such as pancreatitis).
Always follow medical advice and never source injectable medications online without a prescription.
Weight-loss injections work best when combined with changes in eating habits, activity levels, and behaviour. Medicspot’s clinicians and health coaches support this by helping patients set realistic goals and build sustainable routines.
See our resources on Diet and Nutrition
See our resources on Activity and Exercise
See our resources on Behaviour Change
People who combine medical treatment with coaching and lifestyle changes tend to achieve longer-term success.
Based on the results of a clinical study with 806 participants.
If you’re interested in learning whether weight-loss injections could be suitable for you, take our free, confidential assessment to find out more about your options.
Take your free weight-loss assessment
Learn more about Wegovy and Mounjaro, two licensed GLP-1 treatments available in the UK.
Brand names are provided for educational purposes only. Medicspot does not promote any specific prescription-only medicine.
Learn more about the different types of weight loss injections, their active ingredients, side effects, pro's and con's, and whether you can get them on a private prescription.
Tirzepatide is one of the newer weight loss injection treatments, and has become our most popular treatment under the brand name Mounjaro. It's one of the most effective and popular weight loss injections in the UK. Read more...
Semaglutide injections can help you lose weight more effectively and more sustainably than just dieting alone. In this guide we’ll tell you everything you need to know about semaglutide injections like Wegovy and Ozempic. Read more...
Liraglutide injections like Saxenda and Victoza can help you lose weight effectively and sustainably. Read our liraglutide guide for you everything you need to know about this type of weight loss injection. Read more...
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