Does Mounjaro Affect Contraception?

Mounjaro works partly by slowing gastric emptying, meaning food and medicines can remain in the stomach for longer.

This effect is useful as part of the way tirzepatide supports weight management, but it can also influence the absorption of medicines taken by mouth.

Studies of tirzepatide and a combined oral contraceptive found changes in how quickly and how much of the contraceptive hormones were absorbed following a dose of tirzepatide. There is limited information about what this means for contraceptive effectiveness in women with overweight or obesity.

Because reduced effectiveness cannot be ruled out, additional precautions are recommended at certain stages of Mounjaro treatment.

If you use the contraceptive pill and have overweight or obesity, current UK guidance recommends additional precautions for four weeks after your first Mounjaro dose.

You should also take the same precautions for four weeks after each dose increase.

During these periods, you can either use an additional barrier method, such as condoms, or switch to a non-oral contraceptive method.

This advice matters because Mounjaro doses are normally increased gradually. Treatment generally begins at 2.5mg once weekly for four weeks before increasing to 5mg, with further increases possible where appropriate.

You may therefore need additional contraception more than once during the dose-escalation period.

The specific concern relates to oral contraception because these medicines have to pass through the digestive system before being absorbed.

Non-oral contraceptive methods do not rely on absorption through the stomach in the same way.

The MHRA gives examples including the contraceptive coil and implant as non-oral alternatives.

Other contraceptive methods can have their own advantages, risks and suitability requirements, so do not change contraception without discussing your options with an appropriate healthcare professional.

If you take a combined oral contraceptive pill, tell your Mounjaro prescriber before starting treatment.

The current advice for women with overweight or obesity using oral contraception is to add a barrier method or move to non-oral contraception for four weeks after starting tirzepatide and four weeks after every dose increase.

Do not simply stop taking your contraceptive pill unless you have been advised to do so.

Adding condoms during the relevant period may be appropriate, or you can discuss whether a non-oral contraceptive method would suit you better.

The same precaution applies to oral contraceptives generally rather than only one particular type of pill.

If you use an oral contraceptive, including a progestogen-only pill, tell your prescriber when discussing Mounjaro.

Your healthcare professional can advise whether you should use additional barrier contraception or consider a non-oral method.

This is especially important because different contraceptive pills have their own rules around timing and missed doses. Do not change how you take your usual contraception without appropriate advice.

The effect of tirzepatide on gastric emptying is greatest around the beginning of treatment and changes with continued use. Increasing the dose can again make the interaction relevant.

Mounjaro is normally increased gradually to improve tolerability.

Patients typically start with 2.5mg once weekly. After four weeks, the dose increases to 5mg, with further 2.5mg increases possible after spending at least four weeks on the current dose.

If your dose is increased several times, you should remember that the four-week additional contraception recommendation applies after each increase, not just when you first begin treatment.

Mounjaro is not a fertility treatment.

However, weight loss can affect reproductive health in some people. This means pregnancy may become possible in circumstances where somebody previously experienced irregular periods or reduced fertility associated with their weight or an underlying condition.

Regardless of whether your menstrual cycle changes, you should not rely on previous difficulty becoming pregnant as contraception.

If avoiding pregnancy is important, use an appropriate contraceptive method throughout treatment and follow the additional precautions relating to oral contraceptives.

Mounjaro should not be used during pregnancy.

The current UK product information states that there are limited data on tirzepatide use during pregnancy and that animal studies have shown reproductive toxicity. It recommends contraception while using the medicine.

If you are planning a pregnancy, tirzepatide should be stopped at least one month beforehand because of how long the medicine remains in the body.

If you become pregnant while using Mounjaro, contact your healthcare professional for advice rather than continuing or changing treatment without guidance.

Mounjaro commonly causes gastrointestinal side effects, particularly while starting treatment or increasing the dose.

Vomiting or severe diarrhoea can create an additional problem for people taking oral contraception because the pill may not be absorbed properly.

The appropriate action depends on which contraceptive pill you use, when you took it and how long the sickness or diarrhoea lasts.

Follow the missed-pill or sickness instructions supplied with your contraceptive and contact a pharmacist or other healthcare professional if you are unsure whether you remain protected.

Do not assume the standard four-week Mounjaro precautions cover every situation involving vomiting or diarrhoea.

Not necessarily.

Using condoms alongside your oral contraceptive for the recommended four-week periods may be sufficient, depending on your circumstances.

However, if you expect several Mounjaro dose increases, you may prefer to discuss a non-oral method that does not depend on gastrointestinal absorption.

The most appropriate contraception depends on your health, preferences and other risk factors.

A pharmacist, GP or sexual health professional can help you compare the available options rather than changing contraception yourself.

Contraception should form part of the discussion before starting Mounjaro.

Tell your prescriber whether you use the combined pill, progestogen-only pill or another contraceptive method. You should also mention any other prescription medicines, over-the-counter treatments or supplements you take.

You can read more about side effects, contraindications and other Mounjaro safety information before beginning treatment.

Understanding these issues beforehand makes it easier to plan around dose increases and use contraception appropriately.

Mounjaro can be an effective weight-management medicine for suitable patients, but its potential interaction with oral contraception should not be overlooked.

Women with overweight or obesity who take the contraceptive pill should use an additional barrier method or switch to non-oral contraception for four weeks after beginning treatment and four weeks after every dose increase.

If you are considering a prescription injectable treatment for weight management, make sure your prescriber knows which contraception you currently use.

A small amount of planning before treatment starts can help ensure you remain appropriately protected as your Mounjaro dose changes.

Mounjaro can potentially reduce the effectiveness of oral contraception in women with overweight or obesity, particularly when treatment begins and after the dose is increased.

The current recommendation is straightforward: use condoms or another barrier method alongside your pill, or switch to a non-oral contraceptive, for four weeks after starting Mounjaro and four weeks after each dose increase.

Mounjaro should not be used during pregnancy, so reliable contraception is particularly important during treatment.

If you are unsure whether your current contraception is affected, speak to your prescriber, pharmacist, GP or sexual health service before starting Mounjaro.