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    A guide to medicated weight loss

    On this page
    1. What is medicated weight loss?
    2. Types of medicated weight loss
    3. Weight loss pills
    4. At-home weight loss injections
    5. Weight loss surgery
    6. Get help with weight loss

    Reviewed by Dr Bhavini Shah

    A guide to medicated weight loss

    If you’re thinking about losing weight, or you’ve been advised to by your GP, you might be wondering about the best way to go about it. For lots of people, losing weight will be mainly about eating a healthier, balanced diet, reducing calories and exercising more. But for some people, taking medication to aid their weight loss, might also be an option.

    It’s important to remember that weight loss treatments aren’t miracle medications. They work best when you use them with increased exercise and eat as healthily as possible. And lifestyle changes you make while you’re on the treatment, might also make it easier to keep the weight off once you stop it.

    In this article, we’re going to look at some of the main medicated weight loss options available in the UK. We’ll go through a brief weight loss treatment comparison and give some tips on where to get weight loss advice.   

    What is medicated weight loss?

    Medicated weight loss is using medications that can help you lose weight. Weight loss medications work in different ways, depending on the treatment you have. Some work by blocking fat being absorbed into your body from the food you’re eating, and some work by supressing your appetite. 

    Types of medicated weight loss

    In the UK there are four main weight loss treatments. These weight loss treatments are:

    • Orlistat (sometimes known by the branded version Xenical) – a daily pill
    • Mounjaro® - a weekly self-administered injection
    • Saxenda® – a daily self-administered injection
    • Wegovy® – a weekly self-administered injection

    Weight loss pills

    So-called ‘diet pills’ have earned a bad reputation over the years. There have been incidences of people taking drugs branded as weight loss aids, which actually contained unsafe substances and becoming seriously ill or in rare cases causing death. There have also been cases of people taking weight loss pills unsafely and when it’s not clinically appropriate. 

    So, it’s important, if you’re thinking of trying a treatment containing orlistat, you get it from your GP, pharmacy or you can use a regulated, safe online service like Online Doctor. You can find out more about obtaining medicines safely online here

    What weight loss tablets are available

    In the UK the only licensed tablets to help with weight lost are Orlistat, Xenical and

    alli. They all contain the same active ingredient – orlistat. Orlistat and Xenical are prescription-only medications and contain a 120g dose of orlistat. This means a clinician will have to prescribe these for you. alli contains a smaller dose of orlistat (60mg), which means you don’t need a prescription for it. You can request it online or from your local pharmacy, but you will have to answer a couple of pharmacist questions, to make sure it’s safe for you. 

    How weight loss pills work

    Orlistat, the active ingredient in all three of these weight loss pills, works by changing the way fat is absorbed in the body. It blocks around a third of the fat you take in through food and stops it being absorbed. This fat is then passed through your poo. 

    Taking Orlistat/Xenical/alli

    The treatment is taken three times a day. While taking the treatment, you’re advised to reduce your calorie and specifically your fat intake, to give the treatment the best chance of working. You’ll be advised to start a balanced diet and exercise programme before starting the medication, and continue with this during and after your course of treatment. 

    Who’s suitable for weight loss tablets?

    All treatments containing orlistat are only suitable for people:

    • Over 18 years old
    • With a BMI* of 30 or over
    • With a BMI of 28 or over and have another condition that’s a risk factor

    *Your BMI is your body mass index, a measurement taking using your height and weight, to see if your weight is healthy for you. 


    It’s thought that around 45% of people taking 120mg Orlistat/Xenical will lose more than 5% of their body weight, and some people lose up to 10% in the first six months. It’s thought that the 60mg dose has a similar level of effectiveness. 

    Potential side effects

    Like with any treatment, you might experience side effects when taking orlistat. The most common side effects include:

    • Fatty or oily poo
    • Needing to go to the toilet very suddenly
    • Going to the loo more often
    • Oily spotting on your underwear
    • Gas

    If you stick to a low-fat diet while you’re on this treatment, you might find that these side effects are reduced. 

    At-home weight loss injections

    Weight loss injections are a newer type of weight loss treatment in the UK, and they have been proven to be very effective in helping suitable people lose weight. 

    What weight loss injections are available?

    Currently in the UK, the weight loss injections available are Mounjaro®, Wegovy® and Saxenda®.

    How weight loss injections work

    Both Saxenda® and Wegovy® work in the same way to help you lose weight – they suppress your appetite. This means after eating, you feel fuller for longer and generally feel less hungry.

    Mounjaro® also suppresses your appetite. This weight loss injection also regulates your blood sugar and the rate at which food leaves your stomach. Helping you to feel fuller for longer and in turn lose weight.

    Taking weight loss injections

    Saxenda®, Mounjaro® and Wegovy® are injections, or ‘pens’, that you have to give yourself. In the case of Saxenda®, it’s a daily injection. Wegovy ® and Mounjaro® only have to be injected weekly.  

    Who are weight loss injections suitable for?

    Saxenda®, Mounjaro® and Wegovy® are suitable for people with:

    • A BMI of 30 and over 
    • A BMI of 27 to 30 and you have another weight-related ‘co-morbidity’ (e.g. high blood pressure, high cholesterol, sleep apnoea)


    Both types of weight loss injection have been studied to find their effectiveness, and when combined with increased exercise and a lower calorie diet, it’s been found that:

    • In a 56-week trial, around 60% of people using Saxenda® lost more than 5% of their body weight.
    • In a 68-week trial, around 85% of people using Wegovy® lost more than 5% of their body weight. 
    • In a 72-week trial, around 96% of people using Mounjaro® lost more than 5% of their body weight. 

    Potential side effects to weight loss injections

    Saxenda®, Mounjaro® and Wegovy® side effects vary, but they can cause nausea, headaches, diarrhoea and vomiting. 

    Find out more about the individual treatments by visiting our Mounjaro®Saxenda® and Wegovy® info pages. 

    Weight loss surgery

    Not so much a treatment, but a medical intervention, weight loss surgery is sometimes used to help people who are severely overweight. 

    The surgery itself, known as bariatric or metabolic surgery, is a major operation, and the decision to have this will not be taken lightly. 

    You’ll only be considered for bariatric surgery on the NHS if:

    • You have a BMI over 40
    • You have a BMI between 35 and 40 and have another weight-related ‘co-morbidity’ (e.g. high blood pressure or type 2 diabetes)
    • You agree to making lifestyle changes, and attending regular check-ups, long-term

    Weight loss surgery can lead to drastic weight loss, within a few years, but it’s important that you support the surgery but eating a balanced diet and trying to get more exercise. 

    Types of weight loss surgery

    There are three common types of bariatric surgery, these are:

    • Gastric band: a band placed around your stomach to stop you eating as much.
    • Gastric bypass: the top bit of your stomach is joined to the small intestine, effectively making your stomach smaller, so you feel fuller quicker. 
    • Sleeve gastrectomy: part of your stomach is removed, so you can’t eat as much. 

    Potential risks of weight loss surgery

    Like with any major surgery, there are always risks. Some of the more common complications you should consider include:

    • You might end up taking vitamins and supplements for the rest of your life, as the surgery can stop your body getting the vitamins it needs. 
    • You might get gallstones
    • You run the risk of blood clots in the legs
    • Your gastric band could slip and cause issues, like making the small intestine become blocked or narrow
    • You might want further surgery if you’re left with excess folds of skin – this isn’t typically covered by the NHS. 

    Get help with weight loss

    If you’re looking for advice and support on weight loss, it’s a good idea to speak to your GP or pharmacist.

    If you qualify for Orlistat, Xenical, Mounjaro®, Wegovy® or Saxenda®, you can also use online services like Online Doctor. You’ll go through a short consultation online, to make sure the treatment is right for you. If suitable, you'll collect your first treatment in-pharmacy. 


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