If you are using or considering Mounjaro (tirzepatide) and take a hormonal contraceptive, this is an important topic to understand. Mounjaro may reduce the absorption of oral contraceptives during certain stages of treatment, and current UK guidance explains what you should do if this applies to you.
This page explains the latest guidance, what it means for the pill, the coil, the implant and other contraceptive methods, and what to discuss with your prescriber before starting treatment.
This information is for general guidance only and does not replace personalised advice from your prescriber or pharmacist. Whether Mounjaro is suitable for you, including advice about contraception, should always be based on an individual clinical assessment.
The Short Answer
Yes. Mounjaro can reduce the effectiveness of oral hormonal contraceptives, including combined oral contraceptive pills and progestogen only pills.
In June 2025, the MHRA advised that people taking tirzepatide should use a non oral contraceptive method, or add a barrier method such as condoms, for 4 weeks after starting Mounjaro and for 4 weeks after every dose increase.
This recommendation is included in current UK guidance and should be followed if you use an oral contraceptive.
Contraceptive methods that do not rely on being swallowed and absorbed through the digestive system, such as the coil, implant and contraceptive injection, are not expected to be affected by this interaction.
Why This Interaction Happens
Mounjaro works in part by slowing stomach emptying. This means that food and medicines taken by mouth stay in the stomach for longer before moving into the intestine, where they are absorbed.
While this helps support appetite control, it may also affect how oral medicines, including oral contraceptives, are absorbed. This effect is thought to be greatest during the first few weeks after starting treatment and after each dose increase.
A pharmacokinetic study looking at this interaction found around a 20% reduction in overall exposure to oral contraceptives after a single 5 mg dose of tirzepatide, with peak concentrations reduced by up to 66%. Because of these findings, both the manufacturer's prescribing information and current UK guidance include specific recommendations about contraception.
Why This Does Not Apply to All Weight Loss Injections
It is important to know that this guidance does not apply to every weight loss injection.
Current evidence suggests that semaglutide, liraglutide and dulaglutide have not been shown to affect the absorption of oral contraceptives in the same way.
Tirzepatide works on both GLP 1 and glucose dependent insulinotropic polypeptide pathways and appears to slow stomach emptying more than some other medicines in this group, particularly after the first dose.
For this reason, the current contraceptive guidance is specific to tirzepatide rather than applying to all weight loss injections.
Mounjaro and the Contraceptive Pill
Combined Oral Contraceptive Pill
If you take a combined oral contraceptive pill, current UK guidance recommends using a barrier method, such as condoms, or switching to a non oral contraceptive method for 4 weeks after starting Mounjaro and for 4 weeks after every dose increase.
This advice applies because combined oral contraceptive pills are taken by mouth and rely on normal absorption through the digestive system.
Progestogen Only Pill (Mini Pill), Including Desogestrel, Cerazette and Cerelle
The same advice applies to progestogen only pills, including desogestrel tablets and branded medicines such as Cerazette and Cerelle.
As these contraceptives are taken by mouth, delayed stomach emptying may reduce how they are absorbed. Current guidance recommends using additional barrier contraception or choosing a non oral contraceptive method during the 4 week periods after starting Mounjaro and after each dose increase.
If you experience vomiting or diarrhoea while taking the pill, this may also affect how well your oral contraceptive works. If this happens, follow the patient information leaflet supplied with your contraceptive and speak to your prescriber or pharmacist if you are unsure about what to do next.
Mounjaro and Non Oral Contraceptive Methods
The Coil (Mirena and Other IUDs/IUS)
The coil, whether it is a hormonal IUS such as Mirena or a non hormonal copper IUD, does not rely on being taken by mouth or absorbed through the digestive system.
Current UK guidance does not identify Mounjaro as affecting the effectiveness of the coil. Many prescribers and pharmacists recommend the coil, implant, injection or vaginal ring as practical alternatives because these non oral contraceptive methods are not expected to be affected by this interaction.
For people who would prefer to avoid the 4 week precaution periods that apply to oral contraceptive pills, these methods may be suitable options. Speak to your prescriber or pharmacist about which method is right for you.
Contraceptive Implant (Nexplanon)
The same guidance applies to Nexplanon and other contraceptive implants.
Because the hormone is released directly into the bloodstream rather than being absorbed through the digestive system, delayed stomach emptying does not affect how the implant works. Current UK guidance does not identify an interaction between Mounjaro and contraceptive implants, so no additional contraceptive precautions are recommended for this reason.
Contraceptive Injection (Depo Provera)
Depo Provera and other contraceptive injections also release hormones directly into the body rather than relying on oral absorption.
Because they do not depend on the digestive system, they are not expected to be affected by Mounjaro in the same way as oral contraceptive pills. Current guidance does not recommend any additional contraceptive precautions for this interaction.
Mounjaro and Emergency Contraception
If you need emergency contraception while taking Mounjaro, contact a pharmacist, sexual health clinic or healthcare provider as soon as possible. Emergency contraception is time sensitive, so it is important to seek advice without delay.
Emergency contraceptive pills are taken by mouth, so the same theoretical concerns about absorption may apply. However, this has not been studied as extensively as routine oral contraceptives.
When seeking advice, let the healthcare professional know that you are taking Mounjaro, along with any other medicines.
If suitable and available within the recommended timeframe, a copper IUD is not affected by oral absorption and is considered the most effective form of emergency contraception. A healthcare professional can advise on the most appropriate option for your circumstances.
What About Norethisterone?
Norethisterone is often discussed alongside contraception, although it is most commonly prescribed to delay a period rather than as a primary contraceptive method. It should not be relied on for contraception.
As norethisterone is an oral hormonal medicine, similar considerations about absorption may apply while taking Mounjaro.
If you are prescribed norethisterone while taking Mounjaro, let your prescriber know about all the medicines you are taking. They can advise whether your treatment plan needs to be adjusted or whether another option may be more suitable for your individual circumstances.
Quick Reference: Contraception and Mounjaro
| Method | Affected by Mounjaro? | What to Do |
|---|---|---|
| Combined oral contraceptive pill | Potentially, during specific windows | Barrier method or non-oral method for 4 weeks after starting/dose increase |
| Progestogen-only pill (mini pill, desogestrel, Cerazette, Cerelle) | Potentially, during specific windows | Same as above |
| Coil or vaginal ring (Mirena, IUD/IUS) | No | No additional precautions needed for this interaction |
| Implant (Nexplanon) | No | No additional action needed for this interaction |
| Injection (Depo-Provera) | No | No extra precautions needed for this interaction |
| Emergency contraception (morning-after pill) | Possible, not specifically studied | Speak to a pharmacist or clinic immediately to seek advice about emergency contraception ; copper IUD is oral-absorption-independent |
Things to Know Before You Start Mounjaro
- Tell your prescriber which contraceptive method you use during your clinical assessment.
- If you use an oral contraceptive, plan to use a barrier method or consider a temporary switch to a non oral contraceptive method when starting Mounjaro and after each dose increase.
- Mounjaro is not recommended during pregnancy. Effective contraception should be used throughout treatment. If you are planning a pregnancy, speak to your prescriber. Current guidance recommends stopping Mounjaro at least one month before trying to conceive.
- If you vomit within three hours of taking an oral contraceptive pill, its absorption may be affected. Follow the missed dose instructions provided with your contraceptive and speak to your pharmacist if you are unsure what to do.
- If you have severe diarrhoea or vomiting that lasts for more than 24 hours, the effectiveness of an oral contraceptive may be reduced. Speak to a pharmacist or healthcare professional for advice on the next steps.
- Weight loss may improve fertility in some people. If pregnancy is not planned, it is important to use effective contraception throughout treatment.
- If you think you may be pregnant while taking Mounjaro, take a pregnancy test and contact your prescriber as soon as possible. Mounjaro is not recommended during pregnancy, and your prescriber can advise on the most appropriate next steps.
Who Mounjaro Is For
Mounjaro is licensed for long term weight management in adults when used alongside a reduced calorie diet and increased physical activity.
Treatment is suitable for adults who meet the prescribing criteria and should only be started under the supervision of an appropriately qualified prescriber. During your clinical assessment, your prescriber will determine whether Mounjaro is appropriate for you, including discussing your medical history, current medicines, contraceptive method where relevant, and any pregnancy plans.
Your treatment plan, including dose increases and ongoing monitoring, will be tailored to your individual clinical needs.
