Weight loss injections - should you consider them?

Weight loss injections are prescription medicines offered when diet and exercise alone aren't enough to manage excess weight. In the UK, the main options are Wegovy, Mounjaro and Saxenda. They work by suppressing appetite and regulating blood sugar, which helps you eat less and lose weight.

Before prescribing, doctors take into account your BMI, medical history and other conditions. Side effects can range from mild digestive issues to more serious risks, which is why ongoing medical supervision is important. Costs vary, and NHS access is limited, so many people look at private prescriptions instead.

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For anyone looking into medicated weight loss treatments, it's essential to understand how these prescription-only medicines (or POMs, for short) fit into a broader weight management plan and what to expect when a) considering them and b) undergoing treatment.

Of course, talking to your GP should be your first port of call, as they can provide clarity on the most suitable options available for you depending on your current health and medical history.

We spoke to Dr Daniel Atkinson, clinical lead at Treated, to help shed light on when weight loss injections might be the right option for you - and when they’re not.

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What are weight loss injections?

"Weight loss injections are a type of medicine that mimic a hormone your gut makes after you’ve eaten food," explains Dr Daniel. "In short, this hormone, GLP-1, tells your brain you’re full after eating. Weight loss injections also cause food to pass through your gut at a slower rate, again helping you to feel fuller and to lower your appetite.

“By working in this way, using these injections will generally mean you eat fewer calories, helping you to lose weight.”

They’re usually prescribed for people living with obesity or obesity-related health conditions, although licensing varies depending on the type of medication. Ozempic is licensed for type 2 diabetes and Wegovy is licensed for weight management, whereas Mounjaro is licensed for both.

This medicine has been life changing for me as it is the first time I have been able to control my eating.

SevernWonders

How do they compare to other methods of weight loss?

Diet and exercise are still the bedrock of weight management – there’s no getting around that. Weight loss injections can give things a boost if those changes alone haven’t worked, but they aren’t a shortcut. They usually lead to bigger, quicker results than pills, though they also come with side effects and need proper medical supervision. Pills like Orlistat can help some people, but the effects tend to be more modest.

Common types of weight loss injections available in the UK

Several weight loss injections are available across the UK, each licensed for different things and each with unique benefits.

Wegovy (semaglutide): licensed in the UK for weight management only.
Ozempic (semaglutide): licensed for type 2 diabetes, not weight loss, so using it for that purpose is off-label.
Mounjaro (tirzepatide): licensed for both type 2 diabetes and weight management. The active ingredient, tirzepatide, mimics two hormones, GLP-1 and GIP.
Saxenda (liraglutide): also effective but taken daily, rather than weekly.

Each has its own pros, cons and eligibility criteria, so a doctor’s advice is key.

A woman injects her arm with a weight loss pen

Different medications have different licenses for use in the UK

How do weight loss injections work in the body?

Medically speaking, weight loss injections - aka GLP-1 receptor agonists - primarily work by reducing appetite and food intake. They can also improve blood sugar control, which supports weight loss.

Appetite suppression and metabolic effects

Weight loss injections work by making you feel less hungry and more full after eating. They change certain hormones in your body that control appetite, so you naturally want to eat less. These POMs can also help your body burn fat more effectively and make it easier to maintain a healthy weight and BMI.

When you eat less and your body processes food better, it can lead to health improvements like improved blood sugar levels and a healthier heart. The goal is to help people develop eating habits that they can stick with long-term.

I think they have their place and if used correctly can be useful for some people who truly struggle to lose weight and who are at risk of serious health problems because of their weight.

MmePick

Impact on blood sugar and cravings

Keeping your blood sugar steady is key to losing weight - and some weight loss medication can help with this. They improve your body’s response to insulin, helping to stabilise blood sugar. This can indirectly improve blood pressure as weight is reduced.

When your blood sugar is stable, you won't get those sudden cravings for junk food or feel the need to snack constantly. This makes it much easier to stick to eating less without feeling like you're fighting hunger all the time.

As a result, people often find it simpler to follow a healthy diet and avoid overeating, which helps them build better eating habits overall.

Mumsnet users share their experiences

“From my own experience though, I have found it fantastic. I'm on my third week so far of the lowest dose (2.5) of Mounjaro and I have lost a stone without any effort whatsoever. I am still able to eat but just smaller amounts and have no desire to snack or have anything sweet, I've also been lucky to have no side effects so far.” Worried8263839

“I did. Had an appointment with a random GP at my clinic. She was so against it, refused to discuss it. A couple of weeks later I had an appointment with the diabetic doctor. Mentioned it to her, she was very happy to discuss it. As I'm diabetic, she recommended it. Been on Mounjaro since October last year, lost 2 stone and I'm now classed as pre-diabetic.” BrownJenkins

“I've lost 7 stone on Mounjaro. I have lost weight before without drugs but not so easily and not so much weight. I think try other methods first if you haven't but no shame in the injections.” user243245346

“It's for each individual to weigh up the pros and cons and decide for themselves. If they scare you, don't take them then. For me, I was at real danger of developing many life threatening diseases: heart disease, a multitude of cancers, stroke, diabetes. These have all been proved to be caused by obesity. I'm now 5 stone down and have hopefully reduced my risk of developing any of these [...]” Snozzlemaid

“I had my first Mounjaro pen in the fridge for 2 weeks before I actually took it. I was apprehensive to say the least! But, my rationale for taking it was that I’m relatively healthy, it had been prescribed by a pharmacist who was very knowledgeable and thorough when gathering my medical information. Risk of diabetes and heart disease outweighed the risk of the side effects of Mounjaro so when I looked at it in that way it was always going to be a positive [...]” Shallysally

Injections are one part of a healthier diet and exercise regime

Who is eligible for weight loss injections?

Eligibility depends on BMI, health conditions and whether other weight loss attempts have been unsuccessful.

On the NHS, the criteria are stricter than private pharmacies. For example, Wegovy is usually only prescribed to those with a BMI of 35+ and at least one weight-related health problem.

For those going via the NHS, eligibility depends on your BMI, your health and sometimes your ethnicity as per the NICE guidelines:

Medicine	Standard BMI	Extra criteria	Lower BMI for some ethnic groups*	Who prescribes it	Review point
Tirzepatide (Mounjaro)	≥30, or ≥27 with at least one weight-related condition	Yes	Yes	Specialist service / GP in pilot areas	Six months
Semaglutide (Wegovy)	≥35 with a health problem, or 30 to 34.9 with extra criteria	Yes	Yes	Specialist service	Max two years
Liraglutide (Saxenda)	≥35+ with a health problem	Yes	Yes	Specialist service	Three months

*Lower BMI thresholds apply for people of Asian, Chinese, Middle Eastern, Black African or African-Caribbean heritage.

Privately, the threshold is lower. Dr Daniel explains: “They're licensed for people with a BMI of 30 or more, or people with a BMI of 27 or more but with accompanying weight-related risk factors – such as having diabetes, high blood pressure or high cholesterol.

“If someone with a BMI in this range has tried losing weight without treatment – by making changes to their diet and trying to do more exercise – but hasn't been able to bring their BMI down to a healthy range, they might be a suitable candidate for weight loss injections."

Private providers now require either a consultation or supporting GP records before prescribing.

What should I ask my GP before considering weight loss injections?

If you’re considering injections, useful questions include:

Am I a good candidate based on my BMI and health?
Are there any reasons I shouldn’t take them?
Which type is best for me?
How often will I need them, and for how long?
What side effects should I look out for?
How will this affect my current medications?
What support will I have for keeping the weight off long term?

When should you consider weight loss injections?

"There's no set specific time or ‘state of health' really,” says Dr Daniel. “People have different habits and different life events that make every situation for someone trying to lose weight unique.

“But generally, if someone is concerned about their weight but hasn't been able to get to a healthy BMI range through a healthy diet and exercise alone – usually after several attempts – it may be that they could benefit from weight loss injections.”

He adds: “A healthier lifestyle should always be the first port of call when trying to lose weight – even if someone does end up using treatment, they'll need to eat a healthy diet and be physically active for the treatment to be effective.”

Healthier lifestyle habits should be built alongside injections

How much do they cost?

If you qualify for the NHS criteria, prescriptions are free in England (or the standard charge per item).

Otherwise, you'll need to go private. Prices usually range between £150 and £300 a month, depending on the medication and dose. Some clinics charge a flat fee per month to make it easier to budget.

Should injections only be considered after trying other methods?

"Generally, yes”, says Dr Daniel. “A healthier lifestyle should always be the first port of call when trying to lose weight - even if someone does end up using treatment, they’ll need to eat a healthy diet and be physically active for the treatment to be effective."

He’s right - guidance states that medicated weight management should be considered only when traditional methods like diet and exercise have been unsuccessful.

However, it's important to evaluate individual circumstances and consult with a healthcare professional to determine your best approach for sustainable weight management.

Medication can make people's lives better, easier, healthier, however weight loss injections taken without fully understanding the implications, without support or when you really don't fit the prescribing criteria are a recipe for trouble.

wiesowarum

Are there times they shouldn’t be prescribed?

“If someone has an overweight BMI – for example 26 – and wants to start treatment, this is an unlicensed use and it's unlikely they'll be prescribed it,” says Dr Daniel. “In this case, someone may be more able to reach their target weight through different interventions that don't involve treatment – such as diet and exercise.

“If they were still struggling to lose weight after several attempts, they might benefit from a consultation with a dietician.

“Weight loss injections aren't suitable for people with a history of eating disorders. In this case, consulting with a GP is recommended.

“Weight loss injections are contraindicated for people with certain medical conditions too, like pancreatitis, or severe liver or kidney disease. Again in these cases, it's best to ask your GP for advice.”

Moreover, in the UK, the main official contraindication is allergy to the medicine. Doctors may avoid prescribing in people with conditions like pancreatitis or severe organ disease, but these are case-by-case decisions rather than formal contraindications.

What to expect when starting weight loss injections

“It’s unlikely you’ll notice a big change within the first month,” says Dr Daniel. “It’s usually as you start to cycle up through the doses that you’ll notice the treatment becoming more effective, and the number on the scale start to fall at a steadier rate.

“On average, people using the two main treatments – Tirzepatide (Mounjaro) and Semaglutide (Wegovy) – in clinical trials saw a total loss of between 15% and 20% of their starting body weight after a 68 to 72 week period.”

He adds: “In an analysis we conducted at Treated, a significant proportion (42%) of people using these treatments for three to six months had lost at least 10% of their starting weight.”

Safety, risks and potential side effects of weight loss injections

The most common side effects are nausea, diarrhoea, constipation, stomach pain, headaches and tiredness. More serious risks, although less common, include pancreatitis, gallbladder issues and severe dehydration.

People with a history of eating disorders, pancreatitis, certain thyroid cancers or severe liver, kidney or heart disease shouldn't use them. It's also important to flag any other medication you're on, including the contraceptive pill, HRT or insulin, as these may interact.

“Some people do report side effects when using weight loss injections,” says Dr Daniel. “And while these are often mild and pass on their own after a short time when someone has gotten used to the medication, they might be more pronounced for some people.

“Taking these treatments under the supervision of a doctor means you can ask for help and advice if you need it.”

How important is medical supervision?

“Very important”, explains Dr Daniel. “Some people do report possible side effects when using weight loss injections. And while these are often mild and pass on their own after a short time when someone has gotten used to the medication, they might be more pronounced for some people.

“Taking these treatments under the supervision of a doctor means you can ask for help and advice if you need it.”

A woman speaks to her doctor in a treatment room

Medical supervision is very important during treatment

Accessing weight loss injections safely

If you’re thinking about trying weight loss injections, the most important step is making sure you’re getting them from a safe and reliable source. These medicines should only ever be prescribed by a qualified healthcare professional who’s checked your medical history and talked through the risks and benefits with you, and you should also be aware that many insurance companies may have specific coverage criteria.

Don’t buy them from social media or unverified websites. Aside from the fact it’s illegal, you’ve no way of knowing whether the pens are genuine or stored properly – and that can be dangerous.

Whether you go through the NHS or pay privately, you should have a proper consultation (in person or online) and follow-up checks to track your progress and any side effects. If you’re ever unsure, speak to your GP before starting.

How long are they used for?

“Some people may find that they only need to use them for a few months to reach their target weight,” explains Dr Daniel, “and are able to successfully adopt the habits they need to help them stay at that weight.

“Other people may take them for longer than a year, and stay on a maintenance dose for a while after reaching their target weight.

“So they tend to be a longer-term solution – it's unlikely that people will get the most out of treatment when only using it for a few weeks.”

Join the conversation

Want to know how other women are approaching weight loss? Head to the Mumsnet forums to read experiences or start your own thread

Can you regain weight after stopping injections?

Yes. If you struggle to maintain the healthy eating and exercise habits formed while taking weight loss injections, it’s very likely you’ll regain any weight you lost. These medicines aren't designed as a quick fix, but as a tool alongside lifestyle changes.

Useful links for more information

🔎 This article has been medically reviewed

Last reviewed in September 2025 by Dr David Porter MBBS, MSc, PgDip, an internationally renowned sports medicine physician and Founding Director of Opus.

Learn more

About the expert

Dr Daniel Atkinson is the Clinical Lead at Treated.com, an online healthcare service company.

About the author

Our resident Leeds lass, Rebecca Roberts is a Senior Content Editor here at Mumsnet. On a daily basis, she commissions, writes and edits content designed to help parents navigate real life - from product reviews to practical features on everything from sex and relationships to fashion to skincare.

Rebecca - aka Beccy - brings unique personal insight to weight loss content here at Mumsnet, having undergone her own journey with medically supervised injections. Her firsthand experience with GLP-1 treatments provides authentic expertise that resonates with parents exploring similar options.

Beyond her role as an editor, she can be found balancing life as a working mum of two toddlers and when she’s not at her desk, you’ll likely find her at a PTA meeting, in a nearby coffee shop, or walking her two dogs up and down country lanes.