Mounjaro, GLP-1s and Contraception

If you take the contraceptive pill and are starting Mounjaro (tirzepatide), there is one key fact to know: Mounjaro may make oral contraceptives less reliable in people with overweight or obesity. The UK product information and the MHRA advise switching to a non-oral method, such as the coil or implant, or adding a barrier method such as condoms, for four weeks after starting Mounjaro and for four weeks after each dose increase. Separately, the MHRA advises everyone who could become pregnant to use effective contraception while taking any GLP-1 medicine, and to keep using it for a wash-out period after stopping if planning a pregnancy.

Why this matters

GLP-1 medicines are used by many women of reproductive age. Weight loss itself can improve fertility, particularly for people whose periods and ovulation have been affected by excess weight or polycystic ovary syndrome (PCOS). At the same time, these medicines are not recommended in pregnancy because there is not enough information about their safety for a developing baby.

In June 2025, the MHRA issued guidance urging women taking GLP-1 medicines to use effective contraception. The press release stated that Mounjaro may reduce the effectiveness of oral contraceptives in people who are overweight, and stressed that these medicines should not be taken during pregnancy, while trying to conceive or while breastfeeding. The MHRA's patient guidance, updated in February 2026, repeats this advice.

How Mounjaro affects the pill

What the study found

The UK Mounjaro SmPC describes a study in which a combined oral contraceptive was taken alongside a single 5 mg dose of tirzepatide. Compared with taking the pill alone:

The SmPC states that this reduction after a single dose is not considered clinically relevant, and that no adjustment is needed in women with a normal BMI. However, it also states that there is limited information about the effect of tirzepatide on oral contraceptives in women with obesity or overweight. Because reduced effectiveness cannot be excluded, it advises:

• Switching to a non-oral contraceptive method, or
• Adding a barrier method of contraception when starting tirzepatide (for four weeks) and after each dose escalation (for four weeks)

Why it happens

The likely explanation is that tirzepatide slows stomach emptying, which delays and reduces how quickly the hormones in the pill are absorbed. Effects on stomach emptying are strongest when starting treatment and after dose increases, which is why the extra precautions focus on these periods.

Which pills are affected?

The SmPC and MHRA refer to oral contraceptives generally. This includes:

• Combined oral contraceptive pills (containing oestrogen and progestogen)
• Progestogen-only pills (sometimes called the mini-pill)

If you are unsure which type you take, check the packet or ask your pharmacist.

What this looks like in practice

The Mounjaro SmPC sets a starting dose of 2.5 mg once weekly for four weeks, then 5 mg. Further increases, if needed, are made in 2.5 mg steps after at least four weeks on each dose. The table below shows how the extra-protection periods line up with a typical titration if you continue taking the pill. Your own schedule may differ, as many people stay on a dose for longer or do not need the highest dose.

If you restart Mounjaro after a break, or go back up a dose after stepping down, ask your prescriber whether the extra precautions apply again. It is sensible to assume they do unless you are told otherwise.

Common misunderstandings

• "I have a normal BMI now, so the warning does not apply." The SmPC says no adjustment is needed in women with a normal BMI, but many people start treatment with overweight or obesity. As your weight changes, ask your clinician what applies to you rather than deciding yourself.
• "Taking the pill at a different time will fix it." There is no evidence that changing the time you take the pill overcomes the effect of slower stomach emptying.
• "A double dose of the pill will make up for it." Do not take extra pills unless a clinician advises it. This is not a recommended approach.
• "Only the combined pill is affected." The advice refers to oral contraceptives generally, which includes progestogen-only pills.
• "Weight-loss injections make me less fertile, so I do not need contraception." The opposite may be true. Losing weight can restore ovulation in some people.

What about Wegovy, Ozempic and other GLP-1 medicines?

The UK Wegovy SmPC describes a study in which semaglutide did not change exposure to ethinylestradiol and levonorgestrel (a combined pill) to a clinically relevant degree. Based on evidence like this, the Faculty of Sexual and Reproductive Healthcare's Clinical Effectiveness Unit said in a February 2025 statement that there is no need to add a barrier method when using semaglutide, dulaglutide, exenatide, lixisenatide or liraglutide. The Faculty has since been renamed the College of Sexual and Reproductive Healthcare (CoSRH).

That does not mean contraception is unimportant on these medicines. The Wegovy SmPC recommends that women of childbearing potential use contraception during treatment, and the MHRA's advice on effective contraception applies to all GLP-1 medicines.

For oral GLP-1 medicines, such as semaglutide tablets, check the specific product information and ask your prescriber, as advice may differ between products and could be updated. Our oral GLP-1 guide covers tablets in more detail.

Summary of advice by medicine

Always check the latest SmPC, patient leaflet and MHRA guidance, as advice can change.

Contraception options to discuss

There are many methods available in the UK, and the NHS provides contraception free of charge. The right choice depends on your health, preferences and plans. These are some points relevant to GLP-1 treatment.

Methods not affected by stomach emptying

These methods do not rely on absorption through the gut:

• Contraceptive implant: a small rod placed under the skin of the upper arm, lasting up to three years. The MHRA mentions the implant as an option for people on tirzepatide.
• Hormonal coil (IUS): a small device placed in the womb that releases progestogen. Lasts several years depending on type.
• Copper coil (IUD): a hormone-free device placed in the womb. Lasts several years and can also be used as emergency contraception.
• Contraceptive injection: a progestogen injection given every 8 to 13 weeks depending on type.
• Contraceptive patch and vaginal ring: combined hormonal methods absorbed through the skin or vagina rather than the gut. Your clinician will consider whether combined methods suit you (see below).

Implants and coils are long-acting reversible contraception (LARC). The NHS notes that these are among the most effective methods because they do not depend on remembering to take or use them.

Combined hormonal methods and BMI

The combined pill, patch and ring contain oestrogen, which slightly increases the risk of blood clots. The UK Medical Eligibility Criteria for Contraceptive Use (UKMEC) take BMI into account, and combined methods are generally considered less suitable for people with a higher BMI. Your clinician will look at your BMI, blood pressure, smoking status, migraines and other factors. As you lose weight, the options suitable for you may change.

Barrier methods

Condoms (external and internal) and diaphragms are not affected by GLP-1 medicines. Condoms also protect against sexually transmitted infections. Used alone, they are less effective than LARC methods in typical use, but they are a useful addition when the pill may be less reliable.

Emergency contraception

If you have had unprotected sex, or think your contraception may have failed, seek advice promptly. The copper coil is the most effective form of emergency contraception. Emergency contraceptive pills are available from pharmacies, sexual health clinics and GPs. Their effectiveness may be affected by body weight, and there is little specific evidence on how tirzepatide affects them. Tell the pharmacist or clinician that you take a GLP-1 medicine.

Vomiting, diarrhoea and the pill

Nausea, vomiting and diarrhoea are common side effects of all GLP-1 medicines, especially after starting or increasing the dose. Regardless of which GLP-1 you take, severe vomiting or diarrhoea can stop an oral contraceptive being fully absorbed.

The FSRH's 2025 statement said people with severe vomiting or diarrhoea on GLP-1 medicines should follow existing FSRH advice for these situations. Your pill's patient leaflet explains what to do, including when to take another pill and when extra protection is needed. If you are unsure, a pharmacist can advise quickly. Our guide to diarrhoea on GLP-1 medication covers managing this side effect.

Planning a pregnancy

If you are thinking about trying for a baby, talk to your prescriber and GP before stopping contraception. Key points from the MHRA and UK SmPCs:

• Do not take GLP-1 medicines in pregnancy or just before trying to conceive.
• Stop in good time. Tirzepatide should be stopped at least one month before a planned pregnancy, and semaglutide at least two months before, because these medicines stay in the body for some time after the last dose.
• Keep using contraception during the wash-out period.
• Plan for weight changes. Appetite usually returns after stopping, and some weight regain is common. Your GP can help you plan nutrition and activity for a healthy pregnancy.
• Start folic acid. The NHS advises taking folic acid before conception and in early pregnancy. People with a BMI of 30 or more may be advised to take a higher dose, which needs a prescription.

Our guide to GLP-1 medication, pregnancy and fertility covers this in much more detail, including what to do after an unplanned pregnancy.

Breastfeeding

The MHRA's patient guidance states that GLP-1 medicines should not be taken by people who are breastfeeding, owing to insufficient safety data. The Wegovy SmPC states that semaglutide should not be used during breastfeeding.

The current UK Mounjaro SmPC, revised in August 2026, includes newer information from a small study of 11 women, in which tirzepatide levels in breast milk were undetectable or very low after a single dose. On this basis, the SmPC now states that tirzepatide could be considered for use during breastfeeding. This differs from the general MHRA patient guidance published earlier in 2026. If you are breastfeeding or plan to, discuss this with your GP, health visitor or prescriber, who can weigh up the latest information for your situation.

Fertility and GLP-1 treatment

Some people notice their periods become more regular as they lose weight, and fertility may increase. This is a recognised effect of weight loss, particularly in people with PCOS. It means contraception is important even if you have previously had difficulty conceiving. Read more in our guide to GLP-1 medication and PCOS.

Talking to your prescriber

When you are assessed for Mounjaro or another GLP-1 medicine, a responsible prescriber should ask about:

• Whether you could become pregnant
• Your current contraception
• Any plans for pregnancy in the near future
• Whether you are breastfeeding

Be open about these questions. They are there to keep you safe. If you are prescribed privately, consider letting your GP know, as GP practices usually provide contraception and may not know about your GLP-1 treatment otherwise.

If you are comparing regulated online services, our provider comparison sets out how each approaches medical screening and follow-up. We do not rank providers, and treatment decisions rest with a prescriber.

For more on tirzepatide, see our Mounjaro hub, the Mounjaro UK complete guide and the Mounjaro dosing schedule, which explains when dose increases happen.

Reporting side effects and pregnancies

If you have a suspected side effect from a GLP-1 medicine, or become pregnant while taking one, you can report it to the MHRA via the Yellow Card scheme, online or using the app. For Wegovy, the SmPC also asks that any pregnancy be reported to the Novo Nordisk pregnancy registry. These reports help build the evidence about safety in pregnancy.

When to speak to a professional

Speak to a GP, practice nurse, pharmacist or sexual health clinic if:

• You take the pill and are starting Mounjaro or increasing your dose
• You want to switch to a non-oral method such as the implant or coil
• You are planning a pregnancy and need advice on stopping your GLP-1
• You are breastfeeding or plan to

Seek advice promptly (pharmacist, GP or sexual health clinic) if:

• You have had unprotected sex or think your contraception has failed, as emergency contraception is more effective the sooner it is used
• You have had severe vomiting or diarrhoea while relying on the pill

Contact your GP or prescriber straight away if:

• You think you might be pregnant while taking a GLP-1 medicine. Stop the medicine and take a pregnancy test.

Call NHS 111 or seek urgent care if:

• You have signs of dehydration, such as dark urine, peeing less, dizziness or confusion
• You have yellowing of the skin or eyes (jaundice)

Call 999 or go to A&E if:

• You have severe, persistent abdominal pain, especially if it spreads to your back, which may be pancreatitis
• You are pregnant and have heavy bleeding, severe tummy pain, or one-sided pain with shoulder tip pain or dizziness, which could be an ectopic pregnancy

If you are struggling with your mental health or having thoughts of suicide, call NHS 111 (option 2 for mental health in many areas), contact Samaritans free on 116 123, or call 999 in an emergency.