MHRA guidance says tirzepatide (Mounjaro) may reduce how well oral hormonal contraception works. If you take the pill, the advice is to add a barrier method, such as condoms, or switch to a non-oral method, when you start treatment and after each dose increase. Please check the exact current wording on the MHRA website before relying on this article. Don’t stop your pill without advice, because stopping leaves you without protection. And weight loss medicines are not for use in pregnancy, so effective contraception matters while you’re on treatment.

This is general information, not personal medical advice. Speak to a pharmacist or prescriber about your own situation.

The short answer

Does Mounjaro make the pill less effective? It can. Mounjaro slows how quickly food and medicines leave your stomach, which may lower the amount of hormone your body absorbs from an oral contraceptive. The effect has been seen mainly after the first dose and after dose increases. That’s why extra protection is advised during those times.

How long should I use condoms? The MHRA advice is to use a barrier method, or a non-oral contraceptive, for a set period after starting and after each dose increase. At the time of writing that period is 4 weeks, but confirm the current guidance with your pharmacist or the MHRA.

This applies to both the combined pill and the progestogen-only pill, since both are taken by mouth.

Why the pill may work less well

Delayed stomach emptying

Oral contraceptives need to be absorbed from the gut at a steady rate to work reliably. Tirzepatide delays gastric emptying, particularly when you first start and after you step up the dose. In studies, this lowered the levels of hormone absorbed from the pill. The effect is smaller over time, which is why the advice focuses on the weeks after starting and after each increase.

Vomiting and diarrhoea

The other risk is a side effect of the medicine itself. Vomiting or severe diarrhoea can stop the pill being absorbed properly. As a general rule from sexual health guidance, if you vomit soon after taking a pill, or have severe diarrhoea lasting a day or more, you may need to treat it like a missed pill and use extra protection. Check the leaflet for your own pill, or ask a pharmacist, because rules differ between pills.

Our guide to Mounjaro side effects in the UK explains which symptoms are common and when to seek help.

What the MHRA advises

In summary, the MHRA’s advice for people using tirzepatide who take oral hormonal contraception is:

• Switch to a non-oral method, or add a barrier method such as condoms, when starting treatment
• Do the same for a period after each increase in dose
• Be aware that vomiting and diarrhoea can reduce how well the pill works
• Don’t use weight loss medicines in pregnancy, and use effective contraception if you could become pregnant

Guidance can be updated, so read the latest from the MHRA, the Faculty of Sexual and Reproductive Healthcare (FSRH) and the product information (SmPC). Your prescriber should discuss contraception with you before you start. For more on who can be prescribed these medicines, see our guide to weight loss injection eligibility.

Your options

Barrier methods

Condoms are the simplest way to add protection while you carry on with your pill. Use them every time you have sex during the period your pharmacist or prescriber advises. Barrier methods have the advantage of also protecting against sexually transmitted infections.

Non-oral methods

Methods that don’t rely on the gut aren’t affected by delayed stomach emptying. They include the contraceptive injection, implant, intrauterine device (coil) or system, vaginal ring and, for some people, the patch. Suitability depends on your health, preferences and sometimes your weight, so ask a pharmacist or sexual health professional which is right for you. If you’re moving off the pill, make sure the new method is working before you rely on it, and don’t stop the pill until you’re told it’s safe to.

If you’d like to talk this through, book an NHS contraception consultation with Pottery Road Pharmacy.

Planning pregnancy

Weight loss medicines are not for use in pregnancy. If you’re hoping to conceive, talk to your prescriber early so that treatment can be reviewed and stopped at the right time.

If you’re trying to conceive

Don’t wait until you’re pregnant. Your prescriber can advise when to stop and how to plan. Weight loss can also affect ovulation and fertility in some women, which means pregnancy can happen sooner than expected, even if you’ve had irregular periods.

If you think you may be pregnant

Take a pregnancy test and speak to your GP or prescriber promptly. Don’t take another dose until you’ve had advice.

FAQs

Is the injection or patch affected? 

The contraceptive injection and implant don’t rely on the stomach, so the delayed emptying issue doesn’t apply to them. The patch is also non-oral, but its suitability can depend on your weight and health. Ask your pharmacist or sexual health clinic.

Can I use emergency contraception? 

Yes. Emergency contraception is available from many pharmacies, and the type that suits you can depend on timing and other factors. A pharmacist can advise, and the copper coil is the most effective option if you can access it.

What if I vomit after taking my pill? 

Follow the instructions in your pill’s leaflet. If you vomit within a few hours of taking it, you may need to treat it as a missed pill and use extra protection. Ask a pharmacist if you’re unsure.

Should I tell my pharmacist? 

Yes. Tell them about every medicine you take, including contraception, so they can check for interactions and advise on extra protection.

What if I’m trying to conceive? 

Speak to your prescriber before you try, so treatment can be reviewed and stopped at the right time.

Questions about contraception on Mounjaro?

If you’re unsure what applies to you, book an NHS contraception consultation with Pottery Road Pharmacy.