Weight Loss Injections

Weight loss injections are a type of weight loss treatment that has become increasingly popular. They come in the form of an injectable pen which is administered either once a day (Saxenda) or once a week (Wegovy and Mounjaro).

Each weight loss injection pen contains a similar type of active ingredient which mimics a hormone that is released after eating. This can reduce your appetite 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 and for Saxenda your dose will be increased every week, unless you get severe side effects and need to stay on a lower dose for longer. For more information on the dosage schedule for each weight loss injection, check your prescription or patient information leaflet.

As each weight loss injection works similarly, the side effects are also similar. Common side effects of weight loss injections like Mounjaro, Wegovy, and Saxenda 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 Saxenda. They all belong to the same group of medications: glucagon-like peptide 1 (GLP-1) receptor agonists, although Mounjaro also 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. It’s a GLP-1 receptor agonist, which means it sends signals to your brain that you’re full, helping to regulate and reduce your appetite, which in turn helps you lose weight while following a diet plan. It also delays the emptying of your stomach, helping you feel fuller for longer. You take Wegovy once a week, at the same time and day. The Wegovy dosage schedule is increased to a maintenance dose of 2.4 mg.

It was found to be an effective treatment during clinical trials, with around half of people losing 15% or more of their starting weight and 83.5% of people losing 5% or more of their starting weight. This study involved taking the maintenance dose (2.4 mg) for 68 weeks.

The active ingredient in Wegovy, semaglutide, is also used to treat type-2 diabetes (Ozempic), but Wegovy is used specifically for weight loss and you don’t need to have diabetes to take it.

The Mounjaro injectable pen is taken once a week, at the same time and day. It contains the active ingredient tirzepatide, which mimics GLP-1 and GIP. It suppresses your appetite in the same way that Wegovy does and GIP is thought to enhance these effects. It also delays the emptying of your stomach, helping you feel fuller for longer. The Mounjaro dosage schedule is increased to a maximum maintenance dose of 15 mg.

Mounjaro is an effective weight loss treatment according to clinical trials, with people losing up to 22.5% of their starting weight after taking the highest maintenance dose of 15 mg 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 don’t have diabetes, so is not to be mixed up with Mounjaro for diabetes which follows a different dosage schedule.

Saxenda was one of the first weight loss injections to be approved in the UK. It contains the active ingredient liraglutide. It’s a GLP-1 agonist so works like Wegovy and Mounjaro to reduce appetite and delay the emptying of your stomach, making you feel fuller. Saxenda is slowly increased to a maintenance dose of 3 mg a day.

It’s 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. You can switch from Saxenda to Wegovy or Mounjaro with the help of a doctor but you’ll need to wait at least 2 days from taking your last dose.

It’s been found to be an effective treatment for weight loss in clinical trials: Saxenda helped people lose an average of 6.3% of their starting weight after 56 weeks on the 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. Below we compare the 3 UK approved weight loss injections Mounjaro, Wegovy, and Saxenda:

Weight loss injections work by mimicking hormones in your body that are responsible for regulating your appetite and hunger levels: GLP-1 (Mounjaro, Wegovy, Saxenda) 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. It’s important that you still follow a 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.

Weight loss injections are approved after proving to be successful in clinical trials, with more on this data below. Mounjaro, Wegovy, and Saxenda can all help you to lose weight alongside a diet and exercise plan. There are also certain foods it's best to avoid while taking Saxenda, Mounjaro, or Wegovy to improve their effectiveness and get the most from your treatment.

The benefits of weight loss injections include:

• improved weight loss results compared to taking no medication or weight loss tablets
• feeling fuller which helps with following a diet plan
• lower blood sugar levels
• injectable pens are easier to take than having to draw up your medication with a syringe
• can prevent the need for surgery

There are also several benefits of losing weight, including:

• the chances of weight-related medical conditions such as prediabetes will decrease
• improved confidence and self-esteem
• improved mental health if your weight is affecting how you feel
• improved physical health, as obesity can put extra strain on your body, particularly the heart and bones

How effective are weight loss injections?

Weight loss injections are most effective when taken at the maintenance dose, alongside a diet and exercise plan. Below 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 Saxenda, 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.

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:

• orlistat 120 mg tablets - An unbranded, prescription-only treatment that works by reducing the amount of fat that you absorb from your diet. 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 (60 mg) and works in the same way.
• Mysimba - A branded weight loss pill containing 2 ingredients: naltrexone and bupropion. Has 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. Taken on a dosage schedule that slowly increases to 2 tablets, twice a day.

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

• how often they’re taken (weekly - with the exception of Saxenda vs multiple times a day)
• how they’re taken (injections vs orally)
• how they work (reducing appetite vs reducing the amount of fat absorbed from your diet - with the exception of Mysimba 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 weight loss pills don't require a prescription, while all other weight loss pills and injections do.

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. Saxenda prices are the same for each pen and can be bought in bulk. The length of time that each Saxenda pen lasts will depend on which dose you’re currently taking. Saxenda prices at ASDA Online Doctor are:

• 1 pen pack (£55 per pen) - £55.00
• 3 pen pack (£48 per pen) - £144.00
• 5 pen pack (£46 per pen) - £230.00

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 Saxenda.

Weight loss injections work for most people but not everyone can take them. They don’t work on their own so you need to follow a diet and exercise plan too. If a weight loss injection doesn’t work for you, it may just mean you need to try one with a different active ingredient or get further support and advice with your diet and exercise plan.

You’ll also find that weight loss injections are most effective once you reach the maintenance dose.

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 don’t 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 aren’t getting better or are severe: You may need to stay on a lower dose or stop taking the medication.

For an up-to-date, full list of side effects for your weight loss injection, check the patient information leaflet.

Very common and common side effects of weight loss injections include:

• nausea (feeling sick)
• vomiting (being sick)
• diarrhoea or constipation
• headaches
• dizziness
• dry mouth
• injection site reactions, such as itching or redness

Serious weight loss injection side effects include:

• common (Wegovy only): complications of a diabetic eye disease called diabetic retinopathy (only in diabetics)
• uncommon: an inflamed pancreas (acute pancreatitis)
• rare: a serious allergic reaction (anaphylaxis)

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

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. Most weight loss injections are available on the NHS, but only from a specialist weight management service, not your GP.

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:

• Answer a few questions about your health with our online questionnaire, such as past medical history and current BMI.
• One of our doctors will review your questionnaire and provide a treatment plan and prescription, if suitable.
• Your treatment will be delivered straight to your door, with a choice of delivery options depending on the weight loss treatment.
• 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 most weight loss injections on the NHS, although their requirements are slightly different. If a weight loss injection isn’t available on the NHS yet, they usually make it available a few months after private prescription services. To be eligible for a weight loss injection on the NHS, you must have:

• a BMI over 35 kg/m2 or
• a BMI over 30 kg/m2 and a weight-related condition, such as prediabetes

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

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

• Mounjaro has an average rating of 8.3 out of 10 at Drugs.com, with a total of 674 reviews. 78% of people reported a positive experience, while 10% 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.
• Wegovy has an average rating of 7.1 out of 10 at Drugs.com, with a total of 336 reviews. 61% of people had a positive experience, while 21% had a negative one. People reported that it worked well for weight loss with common side effects such as nausea and tiredness.
• Saxenda has an average rating of 7.5 out of 10 at Drugs.com, with a total of 1,439 reviews. 67% of people had a positive experience, while 15% had a negative one. People reported that it had good weight loss results with common side effects such as nausea, vomiting, and constipation.

*This information was correct at the time this page was written (01 March 2024). 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 up to 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.