Mounjaro and Contraception: How Does it Work?

If you’re struggling to lose weight through diet and exercise alone, you may be considering the possibility of a medicated weight loss programme. This is not a decision to be taken lightly, as there are several important factors to consider when determining whether this is a suitable path for you based on your personal circumstances.

For example, weight loss treatments such as Mounjaro may be effective (clinical studies have found the treatment could help you lose up to 22.5% of your starting body weight), but they are not magic solutions and do require hard work and determination to reach your goals. Additional considerations include how the medication could interact with other medicines you may be taking, or what the potential side effects could be and how long they last.

If you’re a woman of childbearing age, pregnancy and contraceptives are also extremely important elements to be taken into account. We’ve discussed the relationship between Mounjaro and pregnancy in another article, but what about the latter?

Join us as we explore Mounjaro and contraception, covering essential areas such as whether the injection can affect contraceptives, what the impact could be, and whether all weight loss injections have the same effects. Let’s begin.  

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Does Mounjaro Affect Contraception?

Tirzepatide (the active ingredient in Mounjaro) doesn’t directly interact with the hormones in oral contraceptives, but it can make these medications less effective. This is because Mounjaro slows the movement of food and other substances through the stomach and can change how your body absorbs certain medications, including contraceptive pills.

However, Mounjaro doesn’t affect all contraceptives the same way, and women using weight loss injections have multiple options available for preventing pregnancy. Here, we’ll discuss the effects of Mounjaro on the combined and mini pill, emergency contraception (i.e., the ‘morning after pill’), and non-oral contraceptives like the ring and patch.

Mounjaro and Contraceptive Pills

Mounjaro doesn’t directly interfere with combined oral contraceptives or mini pills, but it can reduce their efficacy by changing how your body absorbs the medication. Mounjaro and other GLP-1 therapies curb appetite by slowing gastric emptying (i.e., the speed at which food moves through the stomach). This causes food and other substances, including medicines, to sit in the stomach for longer.

This effect makes Mounjaro users feel fuller more quickly and can significantly reduce food intake, but it can also delay the absorption of oral medications. One study observed a 20% drop in overall exposure to a combined oral contraceptive and a reduction in peak blood levels after a single 5 mg dose of tirzepatide. This indicates a substantial effect on the absorption of contraceptive pills and the efficacy of the contraceptive hormones they contain.

If you are using both Mounjaro and oral contraceptive pills, you will need to take additional steps to prevent pregnancy. Doctors advise women taking Mounjaro to add a non-oral, barrier form of contraception (like condoms) for the first four weeks of treatment and in the four weeks following dose increases. Alternatively, you may consider switching to a non-oral contraceptive method (like condoms, hormonal or copper IUDs, contraceptive implants and injections, vaginal rings, or birth control patches), as these are less affected by Mounjaro.

Mounjaro and Emergency Contraception

Doctors don’t yet know how Mounjaro affects emergency contraception. However, as weight loss injections can affect the absorption of oral medications, they may reduce the efficacy of emergency contraception. Some side effects of Mounjaro, such as vomiting, can also stop emergency contraception from working, especially if you are sick within a few hours of taking the pill.

Official NHS advice is to seek medical attention immediately if you vomit within 2 hours of taking Levonelle, or within 3 hours of taking ellaOne, as this may stop the medication from working.

If you are using Mounjaro and require emergency contraception, consult a healthcare professional for advice. They generally recommend the copper IUD (or coil), as this is the most effective form of emergency contraception and isn’t affected by diarrhoea or vomiting. Should oral emergency contraception be considered, your weight or BMI will be taken into account when deciding which option is most appropriate for your circumstances. 

Mounjaro and Contraceptive Patches

Mounjaro may reduce the efficacy of oral contraceptive pills, but there’s no reason to believe weight loss injections affect non-oral contraceptives. Therefore, contraceptive patches, like the Evra patch, will be just as effective whether you’re using a GLP-1 or not.

Contraceptive patches work by releasing contraceptive hormones, which pass through the skin and into the body. They bypass the digestive system, which is the primary target of GLP-1 medications, so they are unaffected by Mounjaro. Evra patches are over 99% effective when used correctly (or around 91% with typical use). For women taking Mounjaro who want to avoid oral contraceptives, the patch may be a viable alternative to the pill.

Mounjaro and the Contraceptive Ring

Mounjaro is unlikely to reduce the efficacy of contraceptive rings, as this is a non-oral form of contraception. Vaginal rings like the NuvaRing are flexible, plastic devices designed to be inserted in the vagina for up to 3 weeks, where they release contraceptive hormones into the blood. As with contraceptive patches, the hormones bypass the digestive system and are unaffected by Mounjaro. Contraceptive rings are more than 99% effective when used perfectly, though the NHS estimates their efficacy to be around 91% with typical use. 

Contraception and Mounjaro at a Glance

Mounjaro affects various forms of contraception differently, and women using weight loss injections may need to reassess their methods to prevent pregnancy. The table below summarises the potential impact of tirzepatide on contraceptives and the efficacy of each form in the presence and absence of Mounjaro.

What is the Best Contraception While on Mounjaro?

The best contraception to use on Mounjaro largely comes down to personal choice, though people using oral contraceptives should consider adding a second, non-oral method to prevent pregnancy.

You can keep using oral contraceptive pills on Mounjaro if you wish to, but weight loss injections may reduce their efficacy. Official UK guidelines recommend that women taking Mounjaro use a second, barrier-form of contraception (like condoms) for the first four weeks of treatment, and for the four weeks following each dose increase. The medication’s effects on digestive function and absorption are most significant during these periods, increasing the likelihood of unintended pregnancy.

If you want to continue taking the pill, you should add condoms or another form of barrier protection during the first four weeks of treatment, and for four weeks after each dose increase. Or, you can use a non-oral form of contraception like a contraceptive ring, patch, injection, implant, or coil. The most effective forms of non-oral contraception, according to the NHS, are the contraceptive implant, hormonal coil (IUS), and copper coil (IUD). All three methods are over 99% effective with typical use, and may be the most reliable ways to prevent pregnancy on Mounjaro.

However, it’s important to note that not all non-oral contraceptive methods start working right away. Always follow your prescribing clinician’s advice carefully and use condoms until you are fully protected against pregnancy.

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Can Mounjaro Side Effects Impact Contraception?

Mounjaro and other GLP-1 therapies often cause diarrhoea and vomiting as side effects, which may impact ‌the absorption and efficacy of oral contraceptives. If you experience severe vomiting or diarrhoea while using weight loss injections and the pill, observe the following clinical recommendations:

• If you vomit within a few hours of taking your pill, or you have severe diarrhoea for more than 24 hours, follow the ‘missed pill’ rules for your contraceptive. You can find these directions in the Patient Information Leaflet (PIL) included in the pill packet.
• If you have persistent vomiting or diarrhoea, consider using non-oral contraception
• Consistently use a barrier form of contraception, like condoms. This is particularly important in the first four weeks of treatment and for four weeks after dose increases.

Is Mounjaro Safe in Pregnancy?

You should not take Mounjaro if you are pregnant or trying to conceive. Doctors don’t know how Mounjaro and other GLP-1 therapies may affect the baby, but some animal studies have found these medicines to be harmful to unborn foetuses. Therefore, you should consistently use reliable contraception throughout Mounjaro treatment.

If you are using weight loss injections and want to become pregnant, speak to a healthcare professional. They will recommend that you continue using contraception for a ‘wash-out’ period of around one month after stopping Mounjaro to make sure the drug is out of your system before you conceive. If you find out that you are pregnant while taking Mounjaro, stop using the medication immediately and make an appointment with your doctor.

Do All Weight Loss Injections Affect Contraception?

Tirzepatide, the active ingredient in Mounjaro, can affect the absorption of oral contraceptive medications and may reduce overall exposure by approximately 20%. However, clinical studies have not found the same effect with semaglutide (Wegovy) or liraglutide (Nevolat). Therefore, you may not need to change contraceptive methods when using these weight loss injections.

However, all GLP-1 medicines have the potential to cause gastrointestinal side effects, including diarrhoea and vomiting, that can impact the absorption and efficacy of contraceptive pills. If you vomit within a few hours of taking your pill, follow the ‘missed pill’ rules for your prescription. If you have persistent diarrhoea and vomiting, use condoms consistently and contact a healthcare professional for further advice. They may recommend that you use non-oral contraception alongside your pill until your gastrointestinal symptoms have passed.

When to Seek Advice on Mounjaro and Contraceptives

Mounjaro can affect the absorption and efficacy of some contraceptives, potentially increasing the likelihood of unintended pregnancy. Doctors don’t yet know how tirzepatide may affect a developing baby, as there has not been enough research on this topic to draw reliable conclusions. Therefore, clinicians advise women using GLP-1 medications to use reliable contraception consistently and to discontinue treatment immediately if they find out they are pregnant.

Understanding your contraceptive choices on Mounjaro is critical for effectively preventing pregnancy. If you’re unsure what to do, make an appointment with your doctor for further advice.

Support Throughout Your Journey

The relationship between Mounjaro and contraception is just one of several things that need to be considered before deciding whether to embark on a medicated weight loss programme with tirzepatide. Other factors include the cost, side effects such as hair loss and sulphur burps, and when to take the treatment. You may even be unsure whether an injection or tablet, such as the Wegovy pill, is more suitable for you.

Whatever the situation, it’s important to ensure you have the right level of support so you can feel completely confident throughout your weight loss journey. This is where Prescription Doctor can help.

Since 2013, we’ve helped countless individuals achieve their goals by creating a programme that’s unique to them and their needs. We begin by assessing your medical history and any other treatments you’re taking to determine whether your chosen treatment is suitable for your circumstances, and continue by offering bespoke advice and support throughout your journey, whenever it is needed. We even dispatch your treatment directly to your designated UK address in plain packaging for complete discretion. It’s therefore no wonder that we’ve cultivated a strong reputation for the quality of our service.

Ready to take your first steps? Start a consultation with Prescription Doctor today. 

Authored By

Kate Latham

Medical Content Writer

Kate has been a scientific content writer since 2017. With a BSc in Biology and a background in cancer research, she is adept at identifying the latest findings in medical research and utilising these

Published on: 15/07/2026

Reviewed By

Mohamed Imran Lakhi

MPharm - Lead Pharmacist

Imran Lakhi is the superintendent pharmacist and founder at Prescription Doctor. He has been at the core of our team.

Reviewed on: 15/07/2026