If you are taking orlistat or Xenical and using hormonal contraception, understanding how these medicines may affect your contraception is the most important point to know.
Short answer: Orlistat does not directly interfere with the contraceptive pill. But orlistat commonly causes diarrhoea, which may stop the pill being absorbed. If you get severe diarrhoea, or diarrhoea lasting more than 24 hours, use barrier contraception such as condoms, and keep using it until 7 days after the diarrhoea has stopped.
This 7-day period after your symptoms improve is often overlooked. The increased risk does not necessarily end as soon as you feel better.
Below, you will find information on orlistat and contraception, fertility and pregnancy, which contraceptive methods may be affected, how generic orlistat compares with Xenical, and the typical cost of each.
Medical disclaimer: This page provides general health information and does not replace personalised medical advice. Orlistat is a prescription medicine that should only be used under the supervision of an appropriately qualified prescriber. It does not give dosing instructions. Treatment suitability depends on individual clinical assessment, and results vary between individuals.
Does Orlistat Interfere with Birth Control?
Orlistat has no direct hormonal interaction with contraception. It is not metabolised in a way that affects oestrogen or progestogen levels, and It does not act on the hormonal pathways used by hormonal contraceptives.
The risk is indirect and entirely about absorption. Orlistat works within the digestive system to reduce the absorption of fat, so around 30% of the fat you eat is not absorbed and passes out in your stool. Diarrhoea is a common side effect. If you have developed severe diarrhoea while taking an oral contraceptive pill, it may pass through your system before it has been absorbed.
The NHS Guidance, Stated Precisely
If you are taking orlistat and the combined pill, be aware that diarrhoea-related effects common with orlistat can happen, though not everyone gets them. If you have severe diarrhoea, or diarrhoea that lasts for more than 24 hours, your contraception may not protect you from pregnancy. Use an additional barrier method of contraception, such as condoms, a diaphragm or cap.
The combined pill guidance goes further on timing. If you have diarrhoea for more than 24 hours, continue taking your pill as normal, and use another type of contraception, such as condoms, until 7 days after your diarrhoea has stopped.
| Situation | What it means |
|---|---|
| Mild, brief loose stools | Standard orlistat side effect, unlikely to affect pill absorption |
| Severe diarrhoea | Treat pill cover as unreliable, use a barrier method |
| Diarrhoea lasting more than 24 hours | Treat pill cover as unreliable, use a barrier method |
| After diarrhoea stops | Continue barrier cover for a further 7 days |
Diarrhoea Just Before Your Pill-Free Break
This is an important detail that is easy to miss. If you have diarrhoea for more than 24 hours while taking the last 7 pills before your pill-free break or before the dummy pills (pills 15 to 21), finish the active pills in your current pack as normal then start your next pack straight away. Do not have a pill-free break, and do not take the dummy pills. Use another type of contraception until you have taken the pill for 7 consecutive days without having diarrhoea.
Does This Apply to Cilique?
Yes. Cilique is a combined oral contraceptive, so the combined pill guidance above applies to it in full. The same is true of other combined pills, whatever the brand name on the packet. If you are unsure which type your pill is, the patient information leaflet will say, or a pharmacist can tell you in seconds.
The Progestogen-Only Contraceptive Pill
The progestogen-only pill, sometimes called the mini pill, is also taken orally and is therefore also subject to absorption problems from diarrhoea. NHS England guidance notes that medicines that cause diarrhoea or vomiting, giving orlistat as an example, could reduce the effectiveness of the progestogen-only pill.
The specific instructions for the mini pill differ from the combined pill, so check the guidance for your particular method or ask a pharmacist rather than assuming the combined pill rules apply.
Which Contraceptive Methods Are Not Affected?
This is the reassuring part, and often the most useful thing for someone deciding how to manage the risk.
| Method | Affected by orlistat-related diarrhoea? |
|---|---|
| Combined pill | Yes, via absorption |
| Progestogen-only pill | Yes, via absorption |
| Contraceptive implant | No, It does not rely on absorption through the gut |
| Intrauterine device or system (coil) | No, not absorbed through the gut |
| Contraceptive injection | No, not absorbed through the gut |
| Contraceptive patch or vaginal ring | Not absorbed through the gut |
If you are planning a long course of orlistat and find the gastrointestinal side effects difficult, you may wish to discuss a non-oral contraceptive method with you GP or a sexual health clinic. Because these methods are not affected by diarrhoea, they may be a more suitable option for some people.
Does Orlistat Affect Fertility?
Short answer: There is currently no evidence that orlistat directly affects fertility in men or women. It works locally in the gut and is not significantly absorbed into the bloodstream, so it does not act on reproductive hormones.
Three things are worth understanding alongside that.
First, contraceptive failure is not a fertility effect. The absorption issue above makes pregnancy more likely, not less. If you are actively avoiding pregnancy, that is the risk to manage.
Second, orlistat is not used in pregnancy. Orlistat is not used during pregnancy as there is not enough information to say it is safe for your baby, and you should tell your doctor if you are pregnant or become pregnant while using it. Orlistat is also not usually recommended while breastfeeding because it is not known whether the medicine passes into breast milk.
Third, weight itself interacts with fertility. For some people with obesity-related fertility difficulties, weight reduction can improve reproductive outcomes. In people with obesity, weight loss may improve ovulation in some people with obesity-related fertility problems, whether they are obese or overweight. Animal studies have suggested possible improvements in sperm parameters, but this has not been shown in humans, but that is not proof of a direct fertility effect in humans. This is not a claim that orlistat improves fertility, and results vary considerably between individuals. It is a reason the overall picture is worth discussing with a clinician rather than reasoning about in isolation.
Can You Take Orlistat While Trying to Conceive?
If you are actively trying to conceive, this needs a conversation with your prescriber rather than a decision made from a web page. The medicine is not used in pregnancy, and a pregnancy could occur before you know about it.
One practical point that most comparison pages miss: orlistat reduces absorption of dietary fat, and this can affect fat soluble vitamins. Some NHS prescribing guidance notes that orlistat may impair absorption of vitamins A, D and E, and that a multivitamin may be considered, taken at least two hours after orlistat or at bedtime to ensure maximum absorption. If you are planning a pregnancy, speak to your doctor or another healthcare professional to make sure your nutritional needs are being met.
Orlistat vs Xenical: What Is Actually Different?
Short answer: There is no clinically meaningful difference. Xenical is the branded version of orlistat. Both contain 120mg of the same active ingredient and work the same way. The difference is price.
| Generic orlistat | Xenical | Alli | Orlos | |
|---|---|---|---|---|
| Active ingredient | Orlistat | Orlistat | Orlistat | Orlistat |
| Strength | 120mg | 120mg | 60mg | 120mg |
| Status | Prescription | Prescription | Pharmacy, lower dose | Pharmacy, lower dose |
| Relative GI side effects | Standard | Standard | Typically milder | Typically milder |
Orlistat is available as Xenical with a prescription, or you can buy it at a lower dose as Alli or Orlos from a pharmacy.
Alli 60mg reduces fat absorption to a lesser extent than the 120mg prescription strength than the 120mg strength. For someone specifically worried about diarrhoea affecting their contraception, a lower-strength option may be associated with fewer gastrointestinal side effects, though it also means a smaller effect on fat absorption. Your prescriber will determine what is appropriate for you.
If You Think You May Have Been Unprotected
If you had unprotected sex during or shortly after a bout of diarrhoea while on the pill, you may need emergency contraception. Speak to a pharmacist, GP or sexual health clinic as soon as possible, or contact NHS 111 for advice. Do not delay, as emergency contraception is most effective when used as soon as possible.
Pricing
| Supply | Generic orlistat 120mg | Xenical 120mg | Difference |
|---|---|---|---|
| 2 weeks | £16.89 | £21.50 | £4.61 |
| 4 weeks | £32.99 | £42.99 | £10.00 |
| 8 weeks | £63.99 | £86.99 | £23.00 |
| 12 weeks | £95.99 | £128.99 | £33.00 |
Alli 60mg is available from £28.99 for 4 weeks.
A discount code (EDM10) offering 10% is currently promoted, bringing the 4-week generic price to £29.69 and Xenical to £38.69. Discount codes change, so treat the table above as the reference and check the live price at checkout.
What the Price Includes
- The medicine at the strength and quantity approved.
- Clinical assessment by a UK-registered prescriber, with a prescription issued where appropriate.
- Dispensing by a GPhC-registered pharmacy.
- The patient information leaflet.
There is no separate GP appointment fee and no separate prescription charge on top of the listed price.
Questions Worth Asking Before Buying Orlistat Online
The NHS advises that if you decide to get a private prescription for orlistat, it is important to check that any bought orlistat online comes from a registered pharmacy, because some websites sell counterfeit weight loss medicines. That makes the following worth checking anywhere you buy:
- Is the pharmacy registered with the General Pharmaceutical Council, with the number displayed?
- Is a named, registered prescriber reviewing your consultation?
- Is the total cost including delivery shown before payment?
- Does the site ask about your other medicines and your contraception?
- What happens if the prescriber declines treatment?
A site that does not ask about your contraception, relevant medical conditions, and other medications before dispensing treatment is not assessing you properly.
Eligibility and How the Process Works
Who Orlistat Is For
Orlistat is generally prescribed only if you have either a body mass index (BMI) of 28 or more and a weight-related condition such as type 2 diabetes or high blood pressure, or a BMI of 30 or more. It may be suitable for adults aged 18 and over who have already tried to lose weight through diet and exercise.
Orlistat may not be suitable if you have had an allergic reaction or serious side effect from orlistat before, if you have a liver condition called cholestasis, or if you have chronic kidney disease or chronic malabsorption syndrome.
If you are weighing up your options more broadly, it is worth reading about the full range of medically supervised weight loss treatments before committing to one, especially if you are starting orlistat.
The Ordering Process
Step 1. Complete the online health questionnaire, including your current medicines and your contraception. Be accurate about the latter, given everything above.
Step 2. A UK-licensed prescriber reviews your answers and may issue a prescription if clinically appropriate.
Step 3. Your treatment is dispensed by the GPhC-registered pharmacy in Leicester.
Step 4. Your order is dispatched with tracked delivery.
Not every consultation results in a prescription. If treatment is declined, the prescriber will explain why.
The 3-Month Review Point
Treatment is usually reviewed after 3 months, and it may be stopped if you have not lost at least 5% of your starting body weight, and your doctor may advise you to stop taking orlistat, stop treatment, and talk to you about other options.
This is worth knowing before you buy a 12-week supply, because it is the natural point at which treatment should be reassessed rather than automatically repeated.
Side Effects and Interactions
Common Side Effects
Common side effects of orlistat include fatty or oily stool, needing to pass stool urgently or more frequently, farting with or without oily spotting, stomach pain and diarrhoea. Orlistat is usually taken with each main meal that contains fat. Follow the instructions provided by your prescriber. You are less likely to get these side effects if you stick to a balanced diet and avoid meals that are very high in fat.
You will need to eat a healthy, calorie-controlled diet with plenty of fruit and vegetables. You will also need to eat some fat while taking orlistat, but avoid foods that are high in fat like processed or fatty meats, fried food, biscuits and cakes.
Serious Side Effects
Orlistat can sometimes cause serious side effects, though most are rare, and there may be an increased risk of complications if severe symptoms are ignored. These include an allergic reaction (anaphylaxis), which may cause symptoms such as a swollen throat or tongue, a raised itchy rash or difficulty breathing, an inflamed pancreas (acute pancreatitis), which can cause severe pain in your tummy or back that does not go away.Severe abdominal pain, and bleeding from the back passage (rectum). If you experience severe diarrhoea or any other serious symptoms, seek urgent medical advice. Call NHS 111 if you are taking orlistat and think you might be having serious side effects.
Side effects can be reported on the MHRA Yellow Card website.
Other Medicines
Some medicines, herbal remedies and supplements may not mix well with orlistat. These include some medicines to prevent blood clots such as warfarin, amiodarone for heart rhythm problems, HIV medicines, medicines for depression or anxiety, and levothyroxine for an underactive thyroid. It can also reduce the absorption of some other medicines because it works in the gut. You may also be told to leave space between each orlistat dose and vitamins or certain medicines. Declare everything you take, including supplements.
Key Takeaways
- Orlistat does not directly interfere with hormonal contraception.
- Severe diarrhoea, or diarrhoea lasting more than 24 hours, means your pill may not protect you, and you should use barrier contraception such as condoms, a diaphragm or cap.
- Continue barrier cover until 7 days after the diarrhoea has stopped.
- Implants, coils and injections are not affected by gut absorption problems.
- There is currently no evidence that orlistat directly affects fertility, but it is not used in pregnancy or usually while breastfeeding.
- Generic orlistat and Xenical contain the same 120mg active ingredient; the difference is price.
- Treatment is usually reviewed after 3 months and may be stopped if sufficient weight loss has not been achieved.
