Safety information · Internal patient-safety page
Orlistat safety summary
Orlistat blocks the enzymes that digest fat, so about a third of the fat you eat passes through undigested instead of being absorbed. It works locally in the gut and is barely absorbed into the body, which is why almost all of its side effects are digestive, and track directly with how much fat is in the meal.
What it's used for
- One 120 mg capsule with each of the three main meals, during the meal or up to one hour after.
- If you skip a meal, or it contains no fat, skip that capsule.
- Spreading your daily fat intake evenly across meals keeps side effects manageable.
- It supports a diet: it does not replace one.
Most common side effects
- Oily spotting from the rectum.
- Wind, with or without oily discharge.
- Fatty or oily stools, and more urgent or more frequent bowel movements.
- Abdominal pain or discomfort.
- They usually ease as you settle into a lower-fat diet.
Serious side effects: stop and seek care
- Yellowing of the skin or eyes, dark urine, pale stools or itching: rare cases of liver inflammation have been reported.
- Severe or persistent abdominal pain.
- Kidney stones: orlistat can increase oxalate absorption.
- Severe allergic reaction (rash, swelling, difficulty breathing).
- Severe or persistent diarrhoea: it can also make other medicines fail (see interactions).
Who should not take it
- Chronic malabsorption syndrome.
- Cholestasis (blocked bile flow).
- Pregnancy or breastfeeding.
- Allergy to orlistat or any capsule ingredient.
Interactions to flag
- Fat-soluble vitamins (A, D, E, K): take a multivitamin at bedtime, well away from the capsules.
- Ciclosporin: levels drop dangerously; the combination should be avoided.
- Levothyroxine: separate by at least 4 hours and watch for thyroid symptoms.
- Warfarin and similar anticoagulants: vitamin-K absorption changes; INR needs closer monitoring.
- Antiepileptics: reduced absorption has led to seizures; tell your doctor.
- Oral contraceptives: use an additional method if you get severe diarrhoea.
Message us in the app chat if you notice any of these
- Yellowing skin or eyes, dark urine or persistent itching: same day.
- Severe abdominal pain.
- Severe or persistent diarrhoea, especially if you take the pill, antiepileptics or anticoagulants.
- Side effects that make you avoid eating rather than eating less fat.
AEMPS CIMA: Orlistat 120 mg
Back to your consultationThis page summarises information from the regulator-approved leaflet for reference only. It is not medical advice and does not replace the assessment of an EU-licensed doctor. Your doctor will review your individual history, dose and interactions during your consultation.