If you are wondering whether you can take orlistat with Mounjaro, there is no established direct drug interaction between them. However, that is not the same as saying that taking both is the right choice for everyone. Whether combining them is appropriate depends on your health, current treatment, side effects, eating pattern and what your prescriber recommends.
This guide is for adults in the UK who want clear, practical information about weight management medicines, especially if you are considering combining orlistat and Mounjaro or switching from one to the other. We will look at how each medicine works, what is known about using them together, how their results compare, which side effects may overlap, and what to discuss with your healthcare professional before starting, stopping or combining either treatment.
That matters because weight management decisions are not just about whether two medicines can technically be taken together. You may also want to know whether adding another medicine is likely to provide enough extra benefit to justify the additional cost, treatment and possible side effects. Your prescriber can help you weigh up these factors rather than relying on online advice.
Key things to know
- There is no established direct interaction between orlistat and Mounjaro, but that does not mean the combination is suitable for everyone
- Using both medicines together is not a standard approach for everyone, and there is limited direct evidence on the combination
- Both medicines can cause gastrointestinal side effects, so taking them together may increase the overall burden of digestive symptoms for some people
- Clinical trials show a difference in average weight loss between tirzepatide and orlistat, but trial results do not predict how much weight one individual will lose
Is There a Known Interaction?
There is no established direct drug interaction between orlistat and tirzepatide. However, this does not mean that you should automatically take them together.
Orlistat works mainly in the gut by reducing the amount of dietary fat that is absorbed. Mounjaro (tirzepatide) works on GIP and GLP 1 receptors and can affect appetite, food intake, gastric emptying and blood glucose regulation. These are different ways of working.
The NHS lists several medicines that may interact with orlistat, including warfarin, amiodarone, some HIV medicines, some medicines for depression or anxiety, and levothyroxine. Tirzepatide is not listed among these medicines. However, you should still tell your prescriber or pharmacist about all medicines, supplements and vitamins you take before starting orlistat.
- This does not make combining the medicines a standard treatment approach
- There is limited direct evidence on using Mounjaro together with another weight management medicine
- Your prescriber should consider your full treatment plan before recommending both medicines
Is Combining Them Actually Worthwhile?
This is a separate question from whether the medicines interact.
Orlistat works by reducing the amount of dietary fat your body absorbs. Its effect therefore depends partly on how much fat is present in your meals. Mounjaro can reduce appetite and food intake, which may mean that you are eating less food and less dietary fat.
If your food intake has already changed considerably while taking Mounjaro, there may be less dietary fat for orlistat to act on. This does not mean that orlistat will definitely have no effect, but its additional benefit may vary from person to person.
There is also the practical question of whether taking two medicines is worthwhile for you. Adding orlistat may mean more tablets, more potential gastrointestinal side effects and an additional cost. Your prescriber can look at your progress, eating pattern and side effects before deciding whether adding another medicine makes sense.
A Genuine Consideration: Side Effects and Fat Soluble Vitamins
Both medicines can cause gastrointestinal side effects.
Orlistat can cause oily or fatty stools, oily spotting, an urgent need to use the toilet and other changes in bowel movements. These effects can be more noticeable after meals containing more fat. The NHS recommends following a healthy, calorie controlled diet while taking orlistat and avoiding high fat foods.
Mounjaro can also cause gastrointestinal side effects, including nausea, diarrhoea, vomiting, constipation and abdominal discomfort. Taking both medicines could therefore mean a greater overall burden of digestive symptoms for some people.
Severe vomiting or diarrhoea can also lead to dehydration. If you develop severe or persistent gastrointestinal symptoms, speak to your prescriber or pharmacist.
Orlistat can reduce the absorption of fat soluble vitamins, including vitamins A, D, E and K. This is why people taking orlistat may be advised to take a multivitamin supplement at a different time from their orlistat dose. Your prescriber or pharmacist can advise you about whether this is appropriate for you.
If you use an oral contraceptive and develop severe diarrhoea while taking orlistat, your contraception may not protect you from pregnancy. The NHS advises using additional barrier contraception, such as condoms, in this situation.
Orlistat vs Mounjaro: An Honest Weight Loss Medications Efficacy Comparison
Clinical trials show that tirzepatide can produce greater average weight loss than orlistat. However, these results come from different clinical studies and should not be treated as a direct head to head comparison.
In the SURMOUNT 1 trial, adults without diabetes who received tirzepatide had estimated average weight reductions of 15.0%, 19.5% and 20.9% at 72 weeks with the 5mg, 10mg and 15mg doses respectively. These are group averages and do not predict the result for an individual person.
Orlistat generally has a more modest effect on body weight. In the Xenical product information, treatment is recommended to be stopped after 12 weeks if a person has not lost at least 5% of their starting body weight.
This does not mean that orlistat has no value. It is a licensed weight management medicine and may be appropriate for some people. The right choice depends on factors such as your health, BMI, other medicines, side effects, preferences and previous treatment.
The medicines also work differently. Orlistat reduces the absorption of dietary fat in the gut. Mounjaro works through GIP and GLP 1 receptors and can affect appetite, food intake and blood glucose regulation.
Switching From Orlistat to Mounjaro
If you are considering switching rather than taking both medicines, speak to your prescriber before making the change.
There is no established direct interaction that requires a specific washout period between orlistat and Mounjaro. However, your prescriber will still need to consider your medical history, current medicines, reason for switching and any side effects you have experienced.
Some people may consider switching because they have not achieved the progress they hoped for with orlistat or because its gastrointestinal side effects are difficult to manage. If this applies to you, tell your prescriber what you have experienced.
Because orlistat prevents fat from being fully absorbed, fewer calories from dietary fat are absorbed. Some digestive effects may become easier to manage as you follow the recommended lower fat eating plan, but this varies between people. Your prescriber can help you decide whether changing treatment is appropriate.
What About Liraglutide and Orlistat?
The same general principles apply when considering liraglutide and orlistat.
Liraglutide, marketed as Saxenda for weight management, is a GLP 1 receptor agonist. Orlistat works differently by reducing the absorption of dietary fat in the gut.
There is no established direct interaction between the two medicines, but that does not automatically mean that taking them together is appropriate. Your prescriber should consider your individual circumstances and the limited evidence available on combining weight management medicines.
If you are weighing up your options, Mounjaro treatment and orlistat are both available through our weight loss treatments, and a genuine consultation can help you discuss which option may be appropriate for you.
Orlistat Pricing
| Product | 4-week supply | With code EDM10 |
|---|---|---|
| Generic orlistat 120mg | £32.99 | £29.69 |
| Xenical 120mg | £42.99 | £38.69 |
Prices update live and may change.
Sources
- NHS: Orlistat, who cannot take it and interactions (nhs.uk/medicines/orlistat)
- Mounjaro (tirzepatide) prescribing information, Eli Lilly and Company
Medical Disclaimer
This page provides general information about orlistat and Mounjaro. It is not a substitute for personalised medical advice, diagnosis, or treatment.
Whether either medicine, alone or together, is appropriate for you should be assessed by a qualified prescriber. Clinical trial results describe groups of people and cannot predict exactly how an individual will respond.
If you have questions about your treatment, side effects or other medicines you take, speak to your prescriber, pharmacist or GP.
