Comparing weight loss pills in the UK

The best weight loss pills available in the UK are ones that have been clinically proven to support weight loss during research. They include:

• Wegovy pill
• Mysimba
• orlistat-containing medications, like generic orlistat, Xenical, Orlos, and alli

These treatments must be approved by a doctor, or a pharmacist in the case of Orlos and alli. This is because they are medical treatments, which are proven to work and which you need to be assessed for by a healthcare professional.

There are 2 main types of prescription weight loss pills available in the UK, appetite suppressants and fat absorption blockers.

Appetite suppressants

Semaglutide, also known as the Wegovy Pill is an appetite suppressant, meaning it makes you feel fuller for longer after eating and makes you less hungry overall. The Wegovy pill does this by mimicking GLP-1, a hormone that controls appetite, blood sugar, and the speed food moves through your digestive system. It’s a daily pill you start on the lowest dose for before increasing

Naltrexone and bupropion, also known as Mysimba, is also an appetite suppressant that acts on the parts of the brain that control your appetite. Naltrexone influences the reward system linked to food while bupropion disrupts hunger signals, causing you to eat less. Mysimba is taken daily with the dose gradually increasing over several weeks.

Fat absorption blockers

Orlistat is a lipase inhibitor or fat absorption blocker that works by blocking the action of the enzyme, lipase, which is responsible for breaking down the fat you eat. So, instead of absorbing it, about a third of the fat you eat is passed out of your body as waste. Orlistat is available under the brand name Xenical and is taken with meals that contain fat up to a maximum of 3 times a day.

Alli and Orlos are also available at Asda Online Doctor, they contain the same active ingredient as Xenical and Orlistat, just at a lower dose. They work in exactly the same way.

Weight loss pills work in different ways, depending on the active ingredients they contain.

How do appetite suppressants work?

Wegovy pill

The active ingredient in the Wegovy pill, semaglutide, works on the brain. It mimics the action of a hormone called GLP-1, which is produced in the gut. GLP-1 affects a number of organs in the body. Itf affects:

• the brain, reduces appetite, food noise, and increasing feelings of fullness after eating
• the pancreas, causing it to release more insulin to control blood sugar and producing less glucagon, which raises blood sugar
• the stomach, slowly down how quickly food leaves the stomach, which increases fullness and further limits blood sugar

Mysimba

The active ingredients in Mysimba, naltrexone and bupropion, work in different ways to suppress appetite and contribute to weight loss:

• naltrexone blocks the rewarding aspects of eating, reduces cravings, and helps you lower your calorie intake
• bupropion appears to directly act on the hypothalamus, the area of the brain responsible for controlling your appetite – it may also play a role in limiting the rewarding feeling you get from eating, reducing cravings

How do fat absorption blockers work?

Orlistat works by reducing the amount of dietary fat absorbed in your intestines by blocking the action of the enzyme responsible for breaking it down – lipase. Orlistat prevents around 33% of dietary fat from being absorbed and allows it to be passed out of the body as waste.

This results in weight loss with research showing that orlistat can help 37% of people lose at least 5% of their starting body weight in 12 weeks when combined with a low-calorie diet.

Here are over-the-counter and prescription weight loss pills currently available in the UK that contain an active ingredient regulated by doctors:

The effectiveness of prescription weight loss pills depends on the active ingredient they contain and how well a person follows their weight loss programme.

Scroll to see the differences.

The Wegovy pill has been shown to help around 79% of people lose at least 5% of their starting body weight and has helped people lose an average of 17% of their starting weight after 64 weeks of treatment.

Orlistat has been shown to help around 37% of people lose at least 5% of their body weight after 12 weeks of treatment when taken alongside a reduced-calorie diet. The studies showed that orlistat is a well-tolerated and effective weight loss treatment.

Mysimba is also an effective weight loss pill which has helped people lose an average of 8.1% of their initial body weight after 56 weeks of treatment. It is most effective for people who are obese or overweight and have at least 1 weight-related health condition, like high blood pressure.

To be eligible for prescription weight loss pills from Asda Online Doctor, your body mass index (BMI) must be:

• 30 or more – for all medications if you do not have a weight-related condition
• for orlistat medications – 28 or more if you have at least one weight-related condition, such as high blood pressure or type 2 diabetes
• for Mysimba and the Wegovy pill – 27 or more if you have at least one weight-related condition, such as high blood pressure or type 2 diabetes

All medications can cause side effects, however, not everybody will get them. Here we look at the most common side effects of weight loss tablets and who should not take them.

Wegovy pills

Common side effects of the semaglutide in the Wegovy pill include:

• feeling sick
• throwing up
• diarrhoea
• constipation
• low blood sugar, for people with type 2 diabetes
• gas
• stomach aches or pains
• heartburn or acid reflux
• burping or bloating
• feeling dizzy
• feeling tired
• headache
• changes to taste
• changes to the way your skin feels
• hair loss

Because the Wegovy pill is absorbed in the stomach, it may cause more stomach-related side effects than injections containing semaglutide.

You should not take Wegovy pills or you should speak to a doctor first if you:

• have an allergy to semaglutide or the other ingredients in the tablets
• are planning a pregnancy (semaglutide should be stopped 2 months before trying for a baby)
• are pregnant or breastfeeding
• have kidney or liver problems
• have diabetes or diabetes related conditions such as retinopathy
• have had pancreatitis
• have severe heart failure
• have severe gastrointestinal disease, including gastroparesis
• have been diagnosed with non-arteritic anterior ischaemic optic neuropathy (NAION)
• have had allergic reactions to other GLP-1 receptor agonists
• are using the contraceptive pill, since side effects like vomiting and diarrhoea can stop the pill being absorbed properly

Mysimba

Very common side effects include:

• feeling sick (nausea)
• being sick (vomiting)
• constipation
• headache

You should not take Mysimba if you:

• are allergic to any of the ingredients
• are pregnant or breastfeeding
• have abnormally high and uncontrolled blood pressure
• have fits (seizures)
• have a brain tumour
• are usually a heavy alcohol drinker
• have recently stopped taking sedatives or anxiety medications
• have or have had bipolar disorder
• are taking any other medications containing naltrexone or bupropion
• have or have had an eating disorder
• are currently dependent on opiates or opiate agonists or in withdrawal
• are taking medication for depression or Parkinson’s disease called monoamine oxidase inhibitors
• have severe liver disease
• have endstage kidney disease

Orlistat/Xenical/alli/Orlos

Very common side effects include:

• headache
• stomach pain
• urgent or increased need to open your bowels
• wind (flatulence) with discharge
• oily discharge
• oily or fatty stools
• diarrhoea
• low blood sugar levels
• respiratory infections and/or flu

You should not take orlistat if you:

• are allergic to orlistat or any of the other ingredients
• have chronic malabsorption syndrome
• have cholestasis
• are breastfeeding or pregnant
• are taking the drug ciclosporin or drugs to thin your blood

Prescription weight loss pills are not the only weight loss treatment available. If you are looking for an over-the-counter treatment, alli and Orlos are lower-dose orlistat pills which are available without a prescription.

Weight loss injections

Weight loss injections can suppress your appetite and make you feel full between meals, so you eat less, promoting weight loss. Weight loss injections, like Mounjaro, Wegovy, and liraglutide are glucagon-like peptide-1 (GLP-1) receptor agonists that bind to GLP-1 receptors and signal to the brain that you feel full.

The effectiveness of weight loss injections depends on the active ingredients they contain:

• Mounjaro contains the active ingredient tirzepatide and can help you lose an average 22.5% of your starting body weight at the highest weekly maintenance dose of 15mg after 72 weeks
• Wegovy contains semaglutide and can help you lose an average 21% of your body weight after 72 weeks using the maximum weekly maintenance dose of 7.2mg
• Nevolat, is a daily weight loss injection that contains the active ingredient, liraglutide, and it can help people lose on average 8% of their body weight after 56 weeks of treatment with the highest maintenance dose

Lifestyle changes

Medical treatments are not the only effective weight loss strategies available. Lifestyle changes are key to an effective weight loss programme, and you’ll need to implement them even if you choose to use weight loss medications.

Some of the lifestyle changes you should consider for weight loss include:

• diet – a calorie-controlled diet is important for any weight loss journey, you should prioritise foods like lean proteins, fruits, vegetables, and healthy fats over processed, sugary, and high-calorie examples
• exercise – increasing your exercise output will burn excess calories and improve your metabolism, and activities like walking, jogging, dancing, strength-based exercises, and yoga can all be beneficial
• stress management – managing stress can be useful, particularly if stress causes you to emotionally eat, such as with techniques like meditation and mindfulness
• sleep – poor sleep can impact your metabolism, making it more difficult to burn calories, and also helps to regulate the production of digestive hormones that control your appetite

To get prescription weight loss pills in the UK, you must have a prescription from a doctor or registered healthcare professional. There are several ways you can obtain prescription weight loss pills in the UK:

Online services

Online doctor services, like Asda Online Doctor, can provide a private prescription for weight loss tablets like the Wegovy pill, orlistat (Xenical, alli, Orlos) or Mysimba following an online consultation with a doctor.

From the NHS

The NHS may be able to prescribe orlistat for individuals who meet the specific criteria.

The Wegovy pill is not available on the NHS.

Mysimba is not available on the NHS, instead, you will need a private prescription to obtain it.

Private clinics

Private clinics and specialist weight management services may offer weight loss pills to those who meet the specified criteria. Like online pharmacies, private clinics must be registered with the CQC and the General Medical Council (GMC).

Picking the right pill for you can be tricky. Weighing up the pros and cons of each can give you a good idea of what to go for:

Scroll to see the pros and cons.