Orlistat
Is It Right for You?
A complete guide to Orlistat — what it treats, how it works, dosages, side effects, and when a clinician may prescribe it following an online consultation.
What Is Orlistat?
Orlistat is a weight-loss medicine that reduces the amount of fat your body absorbs from food. It is used alongside a reduced-calorie, lower-fat diet and increased physical activity to help with weight management.
It is available as 120 mg capsules on prescription (brand name Xenical) and as a lower-strength 60 mg capsule that can be bought from pharmacies (brand name Alli) for certain people.
Orlistat 120 mg is a prescription-only medication in the UK and is used where the BMI meets certain thresholds. A licensed clinician can assess your suitability and prescribe it as part of a weight-management plan through a telehealth consultation.
What Conditions Is Orlistat Used For?
Orlistat is used to support:
in adults who are obese, or overweight with weight-related health risks, alongside diet and exercise.
helping to keep weight off after initial loss when used with ongoing lifestyle changes.
as part of a plan to reduce risks linked to excess weight, such as type 2 diabetes.
Orlistat works only as part of a reduced-calorie, lower-fat diet. Eating high-fat meals while taking it markedly increases unpleasant digestive side effects, so distributing fat evenly across meals is important.
How Does Orlistat Work?
Orlistat blocks enzymes called lipases in the gut. These enzymes normally break down dietary fat so it can be absorbed into the body.
By blocking these lipases, orlistat stops about a third of the fat in your food from being absorbed. The undigested fat passes out of the body in the stools instead of being stored as calories.
Because the unabsorbed fat is what causes most of the side effects, keeping the fat content of your meals moderate makes orlistat both more comfortable and easier to stick with.
Dosages & Administration
The correct dose depends on the type and severity of infection, age, weight, and kidney function. Always follow your clinician's instructions. The table below is for general reference only.
Administration Tips
Take each dose with, or up to one hour after, a main meal containing fat. If you miss a meal or it has no fat, skip that dose.
Take a multivitamin at bedtime, as orlistat can reduce absorption of fat-soluble vitamins (A, D, E, and K). Separate it from the orlistat dose.
Side Effects of Orlistat
Most side effects involve the digestive system and are linked to the unabsorbed fat. They are often worse with high-fat meals.
- Oily or fatty stools
- Urgent need to open the bowels
- Wind, sometimes with oily discharge
- More frequent or loose stools
- Stomach pain
- Difficulty controlling bowel movements
- Severe or ongoing stomach pain
- Signs of liver problems (yellowing skin or eyes, dark urine, severe tiredness, itching)
- Signs of kidney problems
- Severe allergic reaction
- Rectal bleeding
Rarely, orlistat has been linked with liver problems. Stop taking it and seek medical advice if you develop yellowing of the skin or eyes, dark urine, severe tiredness, loss of appetite, or persistent itching.
Drug Interactions
Always disclose all prescription drugs, over-the-counter medicines, vitamins, and supplements to your clinician or pharmacist before starting orlistat.
Orlistat can reduce absorption of ciclosporin; the two should be separated and levels monitored if both are needed.
Orlistat can affect thyroid medicine absorption; doses should be separated and thyroid function monitored.
By reducing vitamin K absorption, orlistat can affect blood clotting and the response to warfarin, which may need monitoring.
Absorption of certain medicines can be reduced; tell your clinician about everything you take so timing can be managed.
Important Warnings
Orlistat reduces absorption of fat-soluble vitamins. Take a daily multivitamin at bedtime, at least two hours away from an orlistat dose, to help maintain your vitamin levels.
If severe diarrhoea occurs, the oral contraceptive pill may be less reliable. Use an additional method of contraception during such episodes.
Orlistat is not suitable for everyone, including people with certain bowel, gallbladder, or absorption problems. Tell your clinician about your medical history.
Orlistat is not recommended during pregnancy or breastfeeding. Tell your clinician if you are pregnant, planning pregnancy, or breastfeeding.
Speak to a Clinician About Treatment
Getting advice no longer means sitting in a waiting room. Through The GP Service, you can consult with a licensed clinician in minutes — from home, on your lunch break, or wherever works for you. If treatment is clinically appropriate, your clinician can issue a prescription during the consultation. A consultation does not guarantee a prescription.
The treatment you need, when you need it.
Orlistat FAQs
Yes. A licensed clinician can assess your BMI, health, and suitability through a telehealth consultation and prescribe orlistat 120 mg as part of a weight-management plan where appropriate.
Orlistat can modestly increase weight loss when combined with a reduced-calorie, lower-fat diet and exercise. It is a support to lifestyle change, not a replacement for it.
Orlistat blocks the absorption of some dietary fat, which then passes out in the stools. Eating lower-fat meals reduces these effects considerably.
Yes. Orlistat only works alongside a reduced-calorie, lower-fat diet and increased activity. High-fat meals reduce its benefit and worsen side effects.
It can affect absorption of some medicines and vitamins. Tell your clinician everything you take so timings can be arranged and any monitoring set up.
Orlistat is usually reviewed after a few months, and continued only if it is helping you lose weight. Your clinician will advise on duration.