Can Orlistat Make You Constipated? UK Pharmacy Guide

Clinically Proven UK Registered Pharmacy

Can Orlistat Make You Constipated? Next Day Delivery UK

UK-registered clinical team
Confidential and secure
No GP visit needed
Fast and discreet delivery
Genuine Products
UK-licensed only
Fast Delivery
Next-day available
Expert Advice
UK pharmacists
Woman using Cured Pharmacy online consultation for weight loss treatment
From £32.00 Starting dose — clinically approved
LIVE PRICING

Our Pricing

Pricing Disclaimer: Prices on some pages may not be up to date — the live pricing table below and pricing shown during consultation are official current prices and take precedence over any other figures on the site.

Orlistat - UK-licensed prescription Treatment
Treatment

Orlistat

From £32.00

Future orders save 5%
Buy Now
Xenical Orlistat 120mg Capsules - UK-licensed prescription Treatment
Treatment

Xenical Orlistat 120mg Capsules

From £49.99

Future orders save 5%
Buy Now
Orlos (Orlistat) 60mg Weight Loss Aid - UK-licensed prescription Treatment
Treatment

Orlos (Orlistat) 60mg Weight Loss Aid

From £22.29

Future orders save 5%
Buy Now
Orlos (Orlistat) 60mg Weight Loss Aid - 84 Capsules - UK-licensed prescription Treatment
Treatment

Orlos (Orlistat) 60mg Weight Loss Aid - 84 Capsules

From £22.29

Future orders save 5%
Buy Now

Understanding Orlistat and Constipation: Clinical Evidence

Published on: June 03, 2026

Many UK patients ask can orlistat make you constipated before starting treatment. While orlistat is primarily associated with loose stools and oily spotting due to its fat-blocking mechanism, constipation can occasionally occur, particularly when patients drastically reduce dietary fat intake. At Cured Pharmacy, our clinical team helps patients understand orlistat's digestive effects and provides genuine UK-licensed orlistat from £32.00 with next day delivery across the UK.

How Orlistat Affects Your Digestive System

Orlistat works by inhibiting pancreatic and gastric lipases, the enzymes responsible for breaking down dietary fat in your intestine [1]. By blocking approximately 25-30% of dietary fat absorption, orlistat prevents these calories from being absorbed, instead allowing undigested fat to pass through your digestive system [1]. This mechanism is why the most commonly reported side effects involve oily stools, increased bowel movements, and faecal urgency rather than constipation.

However, some patients experience constipation when taking orlistat, typically for two reasons. First, if you reduce your fat intake too drastically in an attempt to avoid gastrointestinal side effects, you may inadvertently decrease overall food volume and fibre intake, which can slow bowel transit time [2]. Second, inadequate fluid intake combined with dietary changes can contribute to harder stools and difficulty passing them.

Can Orlistat Make You Constipated? Clinical Evidence

In the landmark XENDOS trial involving over 3,000 patients taking orlistat 120mg three times daily, constipation was reported in approximately 5.2% of participants, compared to 4.5% in the placebo group — a statistically insignificant difference [3]. This suggests that when constipation occurs during orlistat treatment, it's often related to dietary changes rather than the medication itself.

The most common gastrointestinal effects reported in clinical trials were oily spotting (26.6%), flatus with discharge (23.9%), faecal urgency (22.1%), and fatty or oily stools (20.0%) [3]. These effects typically occur when patients consume meals containing more than 30% of calories from fat, as the unabsorbed fat passes through the digestive system.

If you're experiencing constipation while taking orlistat, it's worth reviewing your dietary fibre intake. The MHRA recommends maintaining a balanced diet with adequate fibre and fluid intake throughout orlistat treatment to support normal digestive function [4].

Managing Digestive Side Effects

Our superintendent pharmacist Tarun Kumar advises patients to maintain a diet with approximately 30% of calories from fat, distributed evenly across three main meals. This approach minimises gastrointestinal side effects while ensuring adequate nutrient absorption. Increasing water intake to at least 2 litres daily and consuming 25-30g of dietary fibre from vegetables, wholegrains, and fruits can help maintain regular bowel movements.

Orlistat Dosage Options and Their Effects

Orlistat is available in two strengths in the UK: 60mg (available over the counter as Alli or Orlos) and 120mg (prescription-only as Xenical or generic orlistat). The 120mg prescription strength blocks approximately 25-30% of dietary fat, while the 60mg dose blocks around 25% [1]. Both strengths require you to take one capsule with each main meal containing fat, up to three times daily.

At Cured Pharmacy, we offer Orlos 60mg from £32.00 for patients who meet over-the-counter criteria, and prescription-strength Orlistat 120mg from £32.00 and branded Xenical from £32.00 following a free online consultation with our UK prescribers. The choice between strengths depends on your BMI, weight loss goals, and medical history, which our clinical team assesses during your consultation.

Patients taking the higher 120mg dose may experience more pronounced gastrointestinal effects initially, though these typically diminish within the first few weeks as you adjust your dietary fat intake [2]. Starting with the lower 60mg dose can help you gauge your tolerance before progressing to prescription strength if clinically appropriate.

Product Strength Pack Size Starting Price Prescription Required
Orlos 60mg 84 capsules From £22.29 No (OTC)
Generic Orlistat 120mg 84 capsules From £32.00 Yes
Xenical (branded) 120mg 84 capsules From £32.00 Yes

Comparing Orlistat to Other Weight Loss Treatments

Unlike newer GLP-1 receptor agonist medications that work systemically to reduce appetite and slow gastric emptying, orlistat works locally in your digestive system without entering your bloodstream. This means orlistat doesn't carry the same risk of systemic side effects, making it suitable for patients who cannot tolerate injectable treatments or prefer an oral medication.

The trade-off is that orlistat requires strict adherence to a reduced-fat diet to be effective and to minimise gastrointestinal side effects. Clinical trials show that orlistat combined with a reduced-calorie diet produces an average additional weight loss of 2.9kg compared to diet alone over 12 months [3]. While this is more modest than results seen with newer treatments, orlistat remains a cost-effective option for many UK patients.

Orlistat is particularly suitable if you have a BMI of 28 or above with weight-related health conditions, or a BMI of 30 or above. All prescription medications at Cured Pharmacy require clinical assessment by a UK prescriber to ensure they're safe and appropriate for your individual circumstances.

Who Should Avoid Orlistat

Orlistat is not suitable if you have chronic malabsorption syndrome, cholestasis, or are pregnant or breastfeeding. It should be used with caution in patients taking anticoagulants like warfarin, as reduced vitamin K absorption may affect INR levels [4]. Your Cured Pharmacy prescriber will review your full medical history and current medications during your consultation to ensure orlistat is safe for you.

Preventing Constipation While Taking Orlistat

If you're concerned about constipation or experiencing it during orlistat treatment, several evidence-based strategies can help. First, ensure you're consuming adequate dietary fibre from vegetables, fruits, wholegrains, and legumes. Aim for at least 25-30g of fibre daily, spread across your meals rather than concentrated in one sitting.

Second, maintain proper hydration by drinking at least 2 litres of water throughout the day. Adequate fluid intake is essential for fibre to work effectively in promoting regular bowel movements. Third, don't reduce your fat intake too drastically — while you should limit fat to approximately 30% of daily calories, eliminating fat entirely can paradoxically worsen constipation and reduce absorption of fat-soluble vitamins.

Regular physical activity also supports healthy digestive function. Even moderate exercise like brisk walking for 30 minutes daily can improve bowel transit time and reduce constipation risk. If constipation persists despite these measures, consult your GP or pharmacist before using laxatives, as some may interact with orlistat or mask underlying issues requiring medical attention.

Ordering Orlistat Online from Cured Pharmacy

At Cured Pharmacy, we make accessing genuine UK-licensed orlistat straightforward and discreet. Our free online consultation takes under 3 minutes and is reviewed by UK-registered prescribers who assess whether orlistat is clinically appropriate for you. We offer transparent upfront pricing with no hidden fees — you'll see the exact cost before completing your consultation.

We stock multiple orlistat options to suit different budgets and preferences: Orlos 60mg from £32.00, generic Orlistat 120mg from £32.00, and branded Xenical 120mg from £32.00. All products are sourced from UK-licensed wholesalers and dispensed by our GPhC-registered pharmacy (registration number 9012511). We offer next day delivery across the UK in 100% discreet packaging.

Every prescription medication requires clinical approval from our UK prescribers. Once approved, your medication is dispensed the same day for next day delivery. Our clinical team is available on (+44) 116 4646009 if you have questions about orlistat's side effects, dosing, or suitability for your circumstances. We're committed to supporting your weight loss journey with expert pharmaceutical care and the lowest prices guaranteed in the UK.

What to Expect After Ordering

After your consultation is approved, you'll receive confirmation via email with tracking information for your delivery. Your medication arrives in plain, unmarked packaging with no reference to the contents or pharmacy name. If you experience any unexpected side effects or have concerns during treatment, contact our pharmacy team for advice. Regular follow-up with your GP or our prescribers helps ensure orlistat remains safe and effective for your weight management goals.

Scientific References

  1. Guerciolini, R. (1997). Mode of action of orlistat. International Journal of Obesity, 21(Suppl 3), S12-S23. [accessed 13 August 2026]
  2. Heck, A. M., Yanovski, J. A., & Calis, K. A. (2000). Orlistat, a new lipase inhibitor for the management of obesity. Pharmacotherapy, 20(3), 270-279. https://doi.org/10.1592/phco.20.4.270.34882 [accessed 13 August 2026]
  3. Torgerson, J. S., Hauptman, J., Boldrin, M. N., & Sjöström, L. (2004). XENical in the prevention of diabetes in obese subjects (XENDOS) study: a randomized study of orlistat as an adjunct to lifestyle changes for the prevention of type 2 diabetes in obese patients. Diabetes Care, 27(1), 155-161. https://doi.org/10.2337/diacare.27.1.155 [accessed 13 August 2026]
  4. Medicines and Healthcare products Regulatory Agency. (2009). Orlistat: Summary of Product Characteristics. UK Medicines Information. [accessed 13 August 2026]

Information on this page is for educational purposes only and is not medical advice. All prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting any new medication. Orlistat should be used as part of a comprehensive weight management programme including dietary changes and increased physical activity. Individual results may vary.

Trusted by thousands

Real people, real results

Jane L.

"Brilliant. Lost 4 stone on mounjaro no side effects at all. Cured pharmacy are excellent. Always helpful pens sent out quickly always comes with needles and sterile wipes. If you want to go on GLP-1 go to cured pharmacy. So professional. Thank you cured pharmacy you changed my health and well being."

Ann-Marie

"I absolutely love this product, I have been using 2.5mg as maintenance dose and have managed to control my weight without any side effects and can still eat well balanced meals. The pharmacy is very efficient friendly and helpful I would not purchase from anywhere else."

Sacha W.

"So far I'm really impressed by my results it's crazy cause I'm not snacking like how I used to do and I see my face slimming down already and it's only been 2 and a half weeks. Can't wait to give my feedback in 5 months time thank you cured pharmacy."

Kimberly G.

"Mounjaro has corrected my hormonal weight gain during menopause. I am using it now to maintain that balance. The results for me have been exceptional!"

Jennifer

"Great really helps cure those nasty habits can't wait for my next mounjaro pen."

How it Works?

Select from our recommended UK-licensed medications.

1

Choose your treatment

Step 1: Choose your treatment from Cured Pharmacy

Select safe UK treatments. Quick answers.

2

Answer quick questions

Step 2: Answer quick consultation questions

We will deliver direct to you as quickly as tomorrow.

3

Get it delivered fast

Step 3: Fast discreet delivery to your door

Start Your Assessment For Weight Loss

Start your journey to better health today.

  • Reviewed by UK-based prescribers
  • Takes under 3 minutes
  • Discreet Packaging

Start Your Journey To Better Health Today

Once you complete a short online assessment you will be able to choose your preferred treatment from safe medically approved options tailored to you.

Start My Assessment

Returning Customer?

Log in to Your Account

Faq

Can orlistat make you constipated?
Constipation is uncommon with orlistat, reported in only 5.2% of patients in clinical trials compared to 4.5% on placebo. When it occurs, it's typically due to drastically reduced fat or fibre intake rather than the medication itself.
What are the most common side effects of orlistat?
The most common side effects are oily spotting (26.6%), flatus with discharge (23.9%), faecal urgency (22.1%), and fatty stools (20.0%), particularly when consuming high-fat meals. These effects usually decrease as you adjust your diet to contain approximately 30% fat.
How do I prevent digestive side effects with orlistat?
Maintain a balanced diet with approximately 30% of calories from fat distributed across three meals, consume 25-30g of fibre daily, drink at least 2 litres of water, and take a multivitamin at bedtime (at least 2 hours after your last orlistat dose) to ensure adequate nutrient absorption.
Can I buy orlistat without a prescription in the UK?
The 60mg strength (Alli or Orlos) is available over the counter from pharmacies if you meet specific criteria, while the 120mg prescription strength requires clinical assessment by a UK prescriber. At Cured Pharmacy, we offer both options with appropriate clinical oversight.
How long does orlistat take to work?
Orlistat begins blocking fat absorption immediately with your first dose, but noticeable weight loss typically occurs within 2 weeks when combined with a reduced-calorie diet. Maximum benefit is usually seen after 3-6 months of consistent use with dietary changes.
Is orlistat available for next day delivery in the UK?
Yes, Cured Pharmacy offers next day delivery across the UK for all orlistat products. Once your consultation is approved by our UK prescribers, we dispense and dispatch your medication the same day in discreet packaging.
What's the difference between Xenical and generic orlistat?
Both contain the same active ingredient (orlistat 120mg) and work identically. Xenical is the original branded version priced from £32.00, while generic orlistat offers the same clinical efficacy from £32.00, providing significant savings without compromising quality.
Can I take orlistat if I have irritable bowel syndrome?
Orlistat may worsen IBS symptoms, particularly if you have IBS-D (diarrhoea-predominant). Consult your GP or our prescribers during your consultation to assess whether orlistat is suitable given your digestive health history, as alternative weight loss treatments may be more appropriate.
Tarun Kumar, Prescribing Pharmacist

Medically reviewed by

Tarun Kumar, Prescribing Pharmacist (GPhC 2233073)

Reviewed on: June 03, 2026

Last reviewed: 13 August 2026

Last updated on 13 August 2026.

Review History

Our experts continually monitor new findings in health and medicine, and we update our articles when new information becomes available.

Why this page was updated on 13 August 2026

Content checked and updated as part of our periodic review, to ensure accuracy and currentness.

Current version (13 August 2026)

Edited by: The Editorial Team

Medically reviewed by:

Tarun Kumar, GPhC No. 2233073, Prescribing Pharmacist


How we source info.

When we present you with stats, data, opinion or a consensus, we'll tell you where this came from.