Weight loss injections: A comprehensive guide

Weight loss injections are a type of weight loss treatment that has become increasingly popular due to their effectiveness. They come in the form of an injectable pen, which is injected at home either:

• once a day – Nevolat (liraglutide)
• once a week – Wegovy (semaglutide) and Mounjaro (tirzepatide)

Each weight loss injection pen contains an active ingredient from the same medication family. These are known as glucagon-like peptide 1 (GLP-1) agonists because they mimic the hormone GLP-1, which is released after eating. Mounjaro also mimics a second digestive hormone, which may enhance its effects.

Weight loss injections can reduce your appetite, keep you fuller for longer, and make it easier to stick to a reduced-calorie intake and diet plan. Weight loss injections also follow a dosage schedule until you reach the maintenance dose, which you’ll then stay on. For:

• Wegovy and Mounjaro, your dose will be increased every 4 weeks
• Nevolat, your dose will be increased every week

You may stay on a lower dose for longer if you get severe side effects, and you can also request to stay on a lower dose if you’d prefer. The dosage schedule is there to keep you safe and so your body can adjust to the medication. Although the highest doses provide the highest weight loss results, lower doses can still be effective.

As each weight loss injection works similarly, the side effects are also similar. Very common side effects of the weight loss injections Mounjaro, Wegovy, and Nevolat are nausea (feeling sick), vomiting (being sick), constipation, and diarrhoea.

The different types of weight loss injections available and approved in the UK are Wegovy, Mounjaro, and Nevolat. These are all GLP-1 agonists, although Mounjaro mimics a second hormone called glucose-dependent insulinotropic polypeptide (GIP), making it a dual agonist.

Wegovy (semaglutide)

Wegovy injection for weight loss:

• contains the active ingredient semaglutide, which mimics GLP-1
• sends signals to your brain that you’re full, helping to regulate and reduce your appetite
• delays the emptying of your stomach, helping you feel fuller for longer
• is taken once a week, at the same time and day

The Wegovy dosage schedule is increased to a maximum maintenance dose of 7.2mg.

Wegovy was found to be an effective treatment during clinical trials, with 21% average weight loss over 72 weeks on the 7.2mg dose. 90.7% of people also lost at least 5% of their starting weight.

The active ingredient in Wegovy, semaglutide, is also used to treat type 2 diabetes under the brand name Ozempic, but Wegovy is used specifically for weight loss, and you do not need to have diabetes to take it.

The Mounjaro injectable pen:

• is taken once a week, at the same time and day
• contains the active ingredient tirzepatide, which mimics GLP-1 and GIP
• suppresses your appetite in the same way that Wegovy does, and GIP is thought to enhance these effects
• delays the emptying of your stomach, helping you feel fuller for longer

The Mounjaro dosage schedule is increased to a maximum maintenance dose of 15mg.

Mounjaro is an effective weight loss treatment according to clinical trials, with people losing an average 22.5% of their starting weight after taking the highest maintenance dose of 15mg after 72 weeks. In the same study, 96.3% of people lost at least 5% of their starting weight.

Mounjaro is an approved weight loss injection pen as well as a type 2 diabetes treatment, as tirzepatide can regulate blood sugar too. Mounjaro for weight loss can be taken even if you do not have diabetes, so is not to be mixed up with Mounjaro for diabetes, which follows a different dosage schedule.

The Nevolat injection pen:

• contains the active ingredient liraglutide, which mimics GLP-1
• works like Wegovy and Mounjaro to reduce appetite and delay the emptying of your stomach, making you feel fuller.
• is taken once a day, so Wegovy or Mounjaro may be a good alternative if you’d prefer to only take a weight loss injection once a week instead

Nevolat is slowly increased to a maintenance dose of 3mg a day. It’s the generic version of the brand Saxenda, which means it contains exactly the same active ingredient – the only difference is the branding, price, and non-active ingredients. Saxenda was the first weight loss injection available in the UK.

Nevolat has been found to be an effective treatment for weight loss in clinical trials: it helped people lose an average of 8% of their starting weight after 56 weeks on the 3mg maintenance dose. This is compared to a 0.2% change in starting weight for those taking a placebo.

Comparing weight loss injections

Each weight loss injection pen is slightly different, whether this be the active ingredient, how often you take it, or the dosage schedule. Here compare the 3 UK-approved weight loss injections: tirzepatide, semaglutide, and liraglutide:

Weight loss injections comparison table

Weight loss injections work by mimicking hormones in your body that are responsible for regulating your appetite and hunger levels: GLP-1 (Mounjaro, Wegovy, Nevolat) and GIP (Mounjaro).

These hormones are released after you eat, attaching to receptors that send signals to your brain saying that you’ve eaten and are full. Weight loss injections mimic these hormones, so while taking them you’ll feel fuller even while eating less. They also reduce how quickly your stomach empties after eating, promoting feelings of fullness.

What happens when you stop taking weight loss injections?

When you stop taking weight loss injections, the effects of the medication will slowly wear off. How long this takes will depend on how long you’ve taken the treatment for and what dose you were taking. It can take anywhere from a few days to a few weeks for your hunger levels to return to how they were before. If you used to experience food noise, this could also come back.

It’s important that you still follow a healthy diet and exercise plan so you can maintain your weight loss. If you stop taking a weight loss injection too early, you might put on any weight you’ve lost. You’ll usually follow a weight loss treatment plan until you’ve reached your weight loss goals, but it can be for longer.

How effective are weight loss injections?

Weight loss injections are most effective when taken at the maintenance dose, alongside a healthy diet and exercise plan. Here is a comparison table with the effectiveness of each weight loss injection when taken at the maintenance dose:

If you find that you’re not losing weight on Nevolat, Mounjaro, or Wegovy, there are several reasons why this might be, such as not following the right diet and exercise plan or because you need to give it more time.

➤ For more information on what to eat while taking weight loss injections, see our weight loss injection diet guides:

Both weight loss injections and weight loss pills can be used to safely lose weight alongside a diet and exercise plan. The right treatment for you will depend on what you’d prefer to take, your budget, medical history, and BMI.

The most common weight loss pills are:

• Wegovy pill – a GLP-1 tablet available in the UK, like the Wegovy injection, contains semaglutide. It works to make you feel fuller for longer and lower your cravings. It is taken once daily on an empty stomach.
• orlistat 120mg tablets – an unbranded, prescription-only treatment that works by reducing the amount of fat that you absorb from your diet and can be taken up to 3 times a day, but only with meals containing fat
• Xenical – a branded version of orlistat that works in exactly the same way
• alli – an over-the-counter treatment that also contains orlistat at a lower dose (60mg) and works in the same way
• Orlos – a different branded version of alli, containing 60mg of orlistat and available over the counter
• Mysimba – a branded weight loss pill taken on a dosage schedule that slowly increases to 2 tablets, twice a day, containing 2 ingredients: naltrexone and bupropion, which have a similar effect to weight loss injections, as it works on the parts of your brain responsible for hunger and appetite and can make you feel less hungry

The differences between weight loss injections and weight loss pills are:

• how often they’re taken – weekly (except Nevolat) vs once day (Wegovy pill) vs multiple times a day
• how they’re taken – injections vs by mouth
• how they work – reducing appetite vs reducing the amount of fat absorbed from your diet (except Mysimba and Wegovy pill which also works on appetite)
• effectiveness – weight loss injections often achieve a higher percentage of weight loss than pills

The only other difference is that alli and orlos weight loss pills do not require a prescription, while all other weight loss pills and injections do. However, a pharmacist will still need to complete a short consultation with you to make sure alli or Orlos is safe.

Are weight loss injections safer than pills?

Neither weight loss injections or weight loss pills are ‘safer’ than the other. All medications can cause side effects and shouldn’t be taken if you don’t meet the prescribing criteria, which is why a doctor needs to make sure the treatment is safe. Any approved weight loss treatment is safe to take with a prescription and can be used for a long period of time.

The cost of weight loss injections depends on the injection. Nevolat prices are the same for each pen and can be bought in bulk. The length of time that each Nevolat (liraglutide) pen lasts will depend on which dose you’re currently taking. Nevolat prices at Asda Online Doctor are:

Mounjaro and Wegovy pens are a different price depending on the dosage you’re currently taking. Each Mounjaro and Wegovy pen lasts 4 weeks. The cost for each dose at Asda Online Doctor are as follows:

*The prices on this page were accurate at the time it was written. Check our product pages for the most up-to-date information for Mounjaro, Wegovy, and Nevolat.

Weight loss injections work for most people, but not everyone can take them. They do not work on their own – you need to follow a healthy diet and exercise plan too. If a weight loss injection does not work for you, it may just mean you need to:

• give it more time, as you’ll follow a dosage schedule and may need a higher dose before you get the full effects
• get further support and advice with your diet and exercise plan
• try one with a different active ingredient

You’ll also find that weight loss injections are most effective once you reach the maintenance dose. For more practical tips and advice if you’re not losing weight on weight loss injections and want to look more into the different reasons why, and what you can do, see our guides on liraglutide (Nevolat), Wegovy, and Mounjaro.

Diabetes injections for weight loss

There are some diabetes injections for weight loss that also contain GLP-1 receptor agonists, such as Victoza, Ozempic, and Trulicity. As well as helping with weight loss, GLP-1 can regulate blood sugars as it increases the amount of insulin you produce and decreases the amount of glucose you produce.

Diabetes injections can be prescribed for weight loss and regulating blood sugar if you have diabetes, or off-label as a weight loss treatment if you do not have diabetes.

Like all medications, you may get some side effects while taking weight loss injections. This happens most when you first start taking treatment or after you’ve increased your dose. Weight loss injection side effects tend to go away within a few weeks and get better over time.

Speak to your doctor if side effects are not getting better or are severe. You may need to stay on a lower dose or stop taking the medication.

Very common side effects of weight loss injections include:

Very common side effects usually get better over time, once your body gets used to the medication. These should not be severe and should only last a few weeks at most, but may come back after a dose increase. Let your doctor know about any side effects you get, and keep a diary or log of them to make sure they improve. If you have ongoing side effects, it’s recommended to stay on your current dose to see if they improve first.

Serious weight loss injection side effects include:

Serious side effects need medical attention straight away: Call 999 or go to A&E if you get symptoms of any of these serious conditions.

You can also find out more about side effects, how to manage them, and what to do if you get them in our side effects guides for Wegovy and Mounjaro.

You can buy weight loss injections from online doctor services with a prescription, such as Asda Online Doctor. You can also get weight loss injections in the UK from private doctors, but you’ll always need a prescription. Weight loss injections are also available on the NHS, but only Mounjaro is available from a GP, while Wegovy and Nevolat are available from a specialist weight management service.

How to buy weight loss injections online?

To buy a weight loss injection online, you’ll need a prescription from a doctor. Asda Online Doctor offers prescriptions and weight loss injections, so you can get everything you need in one place. To buy weight loss injections through our service:

1. Answer a few questions about your health with our online questionnaire, such as past medical history and current BMI.
2. One of our doctors will review your questionnaire and provide a treatment plan and prescription, if suitable.
3. Your treatment will be delivered straight to your door, with a choice of delivery options depending on the weight loss treatment.
4. Everything is managed through your free online account, where you’ll have doctor follow-ups and access to our weight loss support package.

Can you get weight loss injections on the NHS?

Yes, you can get weight loss injections on the NHS, although their requirements are slightly different. To be eligible for Wegovy or Nevolat weight loss injections on the NHS, you must have:

• a BMI over 35kg/m2 (or 32.5kg/m2 if you’re of a minority ethnic background)

or

• a BMI over 30kg/m2 and a weight-related condition, such as prediabetes

You can only get a prescription for these weight loss injections on the NHS as part of a specialist weight loss program. Your GP cannot prescribe Wegovy or Nevolat weight loss injections but will refer you to a weight management service instead, so you’ll have to wait for a referral and appointments.

Mounjaro is slightly different and can be prescribed by your GP. However, the guidelines for prescribing it on the NHS are different due to funding and prescriber availability, meaning they are following a 12-year rollout plan and prioritising those most at risk of serious health conditions due to their weight.

At the moment, to get Mounjaro from your GP, you must have:

• a BMI of 40kg/m2 or more (or 37.5kg/m2 if you’re of a minority ethnic background)
• been diagnosed with 4 out of 5 of these weight-related health conditions – high blood pressure, type 2 diabetes, vascular or heart disease, obstructive sleep apnoea, and high cholesterol

The reviews from Drugs.com for each weight loss injection are detailed below*:

• Mounjaro has an average rating of 8.4 out of 10, with a total of 1,835 reviews. 77% of people reported a positive experience, while 6% reported a negative one. People said that tirzepatide worked well for weight loss and helped them to reach their goals, with common side effects like constipation and nausea reported. These reviews are for both Mounjaro as a weight loss medication and a type 2 diabetes medication.
• Wegovy has an average rating of 7.5 out of 10, with a total of 618 reviews. 64% of people had a positive experience, while 17% had a negative one. People reported that it worked well for weight loss, with common side effects such as nausea and constipation.
• Liraglutide (Nevolat) has an average rating of 7.6 out of 10, with a total of 2,339 reviews. 67% of people had a positive experience, while 14% had a negative one. People reported that it had good weight loss results with common side effects such as nausea, headaches, and constipation.

*This information was correct at the time this page was written. Drugs.com allows patients who have taken a treatment to leave a review, so other people can see what it's like to take the medication.

Weight loss injections are a safe and effective weight loss treatment for most people. In some cases, such as Mounjaro, they can help you lose an average of 22.5% of your body weight. The choice between which weight loss injection is best for you will depend on your preferences, medical history, if you’re comfortable injecting yourself, and what your doctor recommends. Mounjaro and Wegovy are the recommended weight loss injections in the UK, as they only need to be taken once a week, rather than daily, and have a higher percentage of weight loss.