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Alli Orlistat

Being overweight is something that can creep up on you over time without you even realising and losing weight can be a tough physical and mental challenge. If you are clinically obese (have a BMI higher than 28) then this can have a serious effect on your health and your ability to enjoy life. These days there are a variety of weight loss programmes available, many of which offer personal or online support. There are also medicines you can take to help you. Whatever you do to lose weight always ensure you are well informed and are following your programme alongside a healthy diet and exercise regime. This medication should not be used if your BMI is normal or low.

What is Alli?

Alli is a medicine you can take to help you on your weight loss journey.

  • Alli contains the active ingredient orlistat.
  • Orlistat works by limiting the action of two enzymes, pancreatic and gastric lipases, that break down the fat in the intestines.
  • These enzymes work to turn the fat into molecules, which are then absorbed into the bloodstream absorbs via the gut.
  • When you take Alli this process is prevented as the orlistat binds itself to the fat that you've eaten and prevents around 3% of the fat in your food from being absorbed.
  • The fat then comes out of your body when you go to the toilet (in your stools).
  • Alli can help you to lose weight more quickly than dieting and exercising alone so it can help with motivation when you have a lot of weight to lose, having a positive effect on your mindset.
  • You will still need to follow a strict diet and exercise regime while taking Alli as it will only work with a calorie and fat controlled diet.
  • This will also benefit you in the long term as successful weight loss requires sticking to lifestyle changes that have a positive influence on your health.

When is Alli used?

Alli is used to help with weight loss in adults over the age of 18 who have a BMI of 28 or over.

It should be taken alongside a healthy diet that has a controlled amount of fat and calories.

How do you use Alli?

Prepare yourself before you start treatment:

  • Choose a start date for the treatment.
  • Start your new lower-calorie, lower-fat diet a few days before you start the treatment;
  • Keep a food diary to help you : it’s a great tool for awareness so you can track exactly what you eat.

Decide on a goal:

  • How much weight do you want to lose? – set a target.
  • Keep it realistic – aim to lose 5-10% of your starting weight at 12 weeks.
  • Aim to lose weight gradually, around 0.5kg per week – this may vary from week to week.

Set calorie intake and fat targets:

  • You will need daily targets for both calorie intake and fat.
  • Calorie intake should be reduced to around 500 calories less per day than your body needs to maintain your current weight;
  • The fat target is worked out by your calorie target. There is a table on the patient leaflet you can use to help you. Once you know your calorie intake target, simply find it to find your fat target;
  • There are lots of easy ways to work out calories and fat in your food these days, including apps which will help you to track this and your total food intake.

Please note:

  • Realistic targets are the best way to maintain weight loss in the long-term.
  • Keep a food diary with notes on the calorie and fat content;
  • Keep active as this is important too, both during your treatment and after;
  • If you are unsure what exercise you can do contact your doctor;
  • Start slowly with exercising and build it up gradually. If you don’t usually walk anywhere then start with that.

What dosages are there?

Alli comes in a 60mg tablet. This means it contains 60mg of orlistat per tablet.

  • Take one tablet immediately before, during or up to one hour after a meal.
  • Swallow each tablet whole with water;
  • Take a tablet at each meal, one capsule at breakfast, lunch and dinner;
  • If you miss a meal or eat a meal with no fat content, then do not take Alli as it only works if there is some fat in the meal;
  • Do not take more than 3 capsules a day;
  • If you eat a high-fat meal, do not be tempted to take a higher dose of Alli as this may increase your chance of side effects;
  • Alli should not be taken for more than six months;
  • If you have not lost any weight after taking Alli for 12 weeks then seek medical advice as you may need to stop taking Alli;
  • You need to maintain the lifestyle changes in order to maintain the weight loss once you are finished with the treatment.

What are the side effects of Alli?

As with all medicines, Alli comes with a warning of some side effects, although not everyone who takes Alli will get them.

Serious side effects include:

  • Severe allergic reactions – look out for breathing problems, sweating, rashes, itching, swelling around the face, mouth and throat, rapid heartbeat or collapse;
  • Inflammation of the large intestine;
  • Skin blistering;
  • Bleeding from your back passage;
  • Inflammation of the pancreas;
  • Severe stomach pain caused by gallstones;
  • Oxalate nephropathy which can lead to kidney stones;
  • Hepatitis.

It is not known how frequent these side effects are.

Very common side effects that may affect more than 1 in 10 people include:

  • Sudden bowel movements;
  • Fatty or oily stools;
  • Wind;
  • Soft stools.

Most of these are caused by the way Alli works and eating a lower-fat diet will help limit them. These side effects are not generally cause for concern.

Common side effects that may affect up to 1 in 10 include:

  • Incontinence (stools);
  • Anxiety;
  • More frequent bowel movements;
  • Stomach pain;
  • Runny/liquid stools.

There are also some side effects that will only show in blood tests:

  • Effects on blood clotting if you take medicine to thin your blood. Like warfarin;
  • Increases in the levels of some liver enzymes.

When shouldn’t you use Alli?

Do not take Alli if you are allergic to orlistat or any of the other ingredients listed on the packet.

Do not take Alli if:

  • You have cholestasis (when the flow of bile between the liver and intestine is blocked).
  • You have difficulties absorbing food;
  • You are pregnant or breastfeeding, or planning to become pregnant;
  • You are under 18 years old;
  • You have a BMI of less than 28;
  • You take medicine to thin your blood (warfarin or similar).

Consult your doctor before taking Alli if any of the following apply:

  • You have a kidney disease – using orlistat may be linked to kidney stones in patients with chronic kidney disease.
  • You have diabetes – you may need to adjust your medicine if you are taking orlistat.

Does Alli interact with other medications?

Like all medicines Alli can interact with other medication, reducing its effectiveness or causing further issues. Always consult a doctor or pharmacist about any other medication you are taking before starting treatment with Alli. This includes herbal medicines and supplements.

Do not take Alli if you are taking any of the following:

  • Warfarin or another medication used to thin the blood.
  • Ciclosporin – used after an organ transplant or to help severe rheumatoid arthritis and some severe skin conditions.

If you are taking a contraceptive pill then use a condom as Alli can cause diarrhoea. Remember to use another method of contraception as you could end up pregnant if you don’t.

Alli can have an effect on the vitamins in your food as it lowers the levels that are absorbed into the body. Take a vitamin supplement to combat this. You should take the supplement at bedtime as you won’t be taking Alli then, so it will be absorbed better.

Take special care with Alli and consult your doctor before starting treatment if you are taking any of the following:

  • Thyroid medicine (levothyroxine) you may need to adjust your dose and take your medication at different times of the day;
  • Amiodarone – for heart problems;
  • Epilepsy medicine – consult your doctor about changes in your convulsions
  • Acarbose – taken for diabetes, Alli should generally be avoided if you have diabetes;
  • Medicines to treat HIV – consult your doctor;
  • Medicines for depression, psychiatric illness or anxiety;
  • Medicines to treat high blood pressure – you may need to change your dose;
  • Medicines to treat high cholesterol – you may need to change your dose.

Where can you buy Alli?

You can buy Alli from any pharmacy or order it online.

Can I get Alli without a prescription?

Yes, you can. It is registered as an over-the-counter medicine meaning you do not need a consultation with a doctor to get a prescription. However, if you are in any doubt about whether Alli is the right medication for you, or you have any other health issues that may prevent you from taking Alli then it is worth seeing a doctor or pharmacist. You can speak to your regular doctor or consult with a doctor online who can offer advice.


GlaxoSmithKline (2018). [online] Available at: [Accessed 21 Jan. 2020].

NHS UK (2019). How your GP can help you lose weight. [online] Available at: [Accessed 21 Jan. 2020].

NHS UK (2019). Obesity - Treatment. [online] Available at: [Accessed 21 Jan. 2020].

Unknown (n.d.). Patient Information Leaflet (PIL) - Alli Orlistat 60mg. [online] Health Info UK. Available at: [Accessed 21 Jan. 2020].

Patient Leaflet(s)

Reviewed by:

Dr Imran Malik, General practitioner Registrationnumber: GMC: 4741365 Last checked: 12-01-2023 | Still valid

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