Mounjaro and the contraceptive pill: the extra precaution you need

In short

Use condoms or switch to a non-oral method for 4 weeks after starting Mounjaro and 4 weeks after each dose increase
The advice covers the combined pill and the progestogen-only pill
The FSRH says tirzepatide reduces oral contraceptive absorption, while semaglutide and liraglutide have no clinically relevant effect
Implants, injections, coils, patches and rings do not rely on the gut and are not affected
Stop Mounjaro at least 1 month before trying to get pregnant

If you take the combined pill or the mini pill, Mounjaro can make it less reliable. Use condoms as well, or switch to a non-oral method, for 4 weeks after your first dose and for 4 weeks after each dose increase. The UK SmPC, the MHRA and the Faculty of Sexual and Reproductive Healthcare (FSRH) all give this advice. Implants, injections, coils, patches and rings are not affected.

Why Mounjaro affects the pill

Tirzepatide slows the emptying of your stomach. A tablet taken by mouth then reaches the gut, where it is absorbed, more slowly and less completely. The SmPC says tirzepatide can reduce the amount of an oral contraceptive reaching the bloodstream.

The FSRH Clinical Effectiveness Unit reviewed the evidence in January 2025. It found tirzepatide significantly reduces absorption of oral contraceptives. It found no clinically relevant effect for semaglutide, liraglutide, dulaglutide, exenatide or lixisenatide. The extra precaution is specific to Mounjaro among the current weight loss injections.

The SmPC also says the slowing of the stomach is most marked at the start of treatment and fades over time. Each dose increase brings a new period of slower emptying. This explains why the advice is tied to starting and stepping up, rather than to the whole course.

What the advice says

When	What to do
First 4 weeks on 2.5mg	Add condoms, or use a non-oral method
Weeks 5 to 8 (first month on 5mg)	Add condoms, or use a non-oral method
First 4 weeks after each later increase	Add condoms, or use a non-oral method
Staying on the same dose after the first 4 weeks	Pill alone is enough, if taken correctly
Going back up after a break	Treat as a new start and use condoms for 4 weeks

Doses rise in 2.5mg steps, with at least 4 weeks on each. If you step up every 4 weeks from 2.5mg to 15mg, the windows join together, and you will need the extra precaution for about 24 weeks in a row. The dose steps guide shows the full schedule.

Keep taking your pill every day during these windows. The barrier method is an addition, not a replacement.

Which methods count

Oral methods (affected)

Combined pill
Progestogen-only pill (mini pill)

Barrier methods (add during the windows)

Male or internal condoms
Diaphragm or cap, used with spermicide

The NHS lists condoms, a diaphragm or a cap as suitable barrier methods for these 4 week periods.

Non-oral methods (not affected)

Implant in the arm
Contraceptive injection
Copper coil (IUD)
Hormonal coil (IUS)
Contraceptive patch
Vaginal ring

The patch and the ring deliver hormones through the skin and the vaginal wall, so a slow stomach makes no difference. The MHRA suggests the coil or implant as options if you would rather not use condoms. The implant, the injection and the coils also remove the risk of missed pills.

If you are sick or have diarrhoea

Nausea, vomiting and diarrhoea are common in the first weeks of Mounjaro, which adds a second risk to the pill. The FSRH advises following the missed pill rules if you vomit within a few hours of taking a pill, or have severe diarrhoea for more than 24 hours. Check your own pill leaflet, as the timings differ between brands. If vomiting or diarrhoea keeps happening, the FSRH suggests considering a non-oral method. The sick day rules cover what to do with your Mounjaro dose when you are ill.

Emergency contraception

If you had sex without a condom during one of the 4 week windows, act quickly. The FSRH says:

The copper coil is the most effective emergency contraception and should be offered where suitable
A double dose of levonorgestrel emergency pill should be considered if your BMI is over 26 or you weigh more than 70kg
There is no direct evidence on how GLP-1 medicines affect emergency pills

A pharmacist, GP or sexual health clinic can help. Do not wait to see whether a period arrives.

Switching from another weight loss injection

If you move from Wegovy to Mounjaro, the precaution applies from your first Mounjaro dose, even if you never needed it on semaglutide. The switching guide explains the dose change.

HRT and other hormone tablets

HRT is a different situation. It replaces hormones rather than preventing pregnancy, and a pill used as HRT does not give contraception. The HRT guide covers Mounjaro alongside menopause treatment. Weight loss can also change your cycle, covered on the periods page.

Planning a pregnancy

The SmPC says tirzepatide should not be used during pregnancy, and you should stop it at least 1 month before a planned pregnancy. Keep using contraception until then. The pregnancy page explains what to do if you find out you are pregnant.

When to get help

Call 999 or go to A&E if you have:

Sudden severe pain low in your tummy on one side with a missed period, or feeling faint, which can be a sign of an ectopic pregnancy

Call 111 or see a GP today if:

You have had sex without a condom during a 4 week window and need emergency contraception
You have a positive pregnancy test while taking Mounjaro
You keep vomiting within a few hours of your pill

Mention at your next check if:

You want to switch to a non-oral method before your next dose increase
You are planning a pregnancy in the next few months
Your periods have changed since starting

Questions people ask

Does Mounjaro stop the pill from working?

It can make the pill less reliable. Tirzepatide slows stomach emptying, and the FSRH says it reduces how much of an oral contraceptive is absorbed. The effect is greatest when you start and after each dose increase, which is why the extra precaution covers those 4 week windows.

Does the mini pill count?

Yes. The SmPC and the FSRH advice apply to oral contraceptives in general, so the progestogen-only pill needs the same 4 week precaution as the combined pill. Keep taking your pill as normal and add condoms, or switch to a non-oral method.

Is the contraceptive patch or ring safe to use with Mounjaro?

Yes. The patch passes hormones through the skin and the ring through the vaginal wall, so they do not rely on the gut. The implant, the injection and both types of coil are not affected either.

Can I use the morning after pill on Mounjaro?

Yes, but the copper coil is the most effective emergency contraception and the FSRH advises offering it where suitable. The FSRH also advises considering a double dose of levonorgestrel emergency pill for people with a BMI over 26 or weight over 70kg. Speak to a pharmacist, GP or sexual health clinic as soon as possible.

Do I need extra contraception if I switch from Wegovy to Mounjaro?

Yes. The FSRH says semaglutide has no clinically relevant effect on the pill, but tirzepatide does. Use condoms or a non-oral method for 4 weeks after your first Mounjaro dose and after each dose increase.

What if I am sick or have diarrhoea while on the pill and Mounjaro?

Follow the missed pill rules in your pill leaflet if you vomit within a few hours of taking it, or have severe diarrhoea for more than 24 hours. The FSRH advises considering a non-oral method if vomiting or diarrhoea keeps happening.

Sources

Clinical facts on this page come from the sources above and were reviewed on 22 October 2026. Mounjaro carries a black triangle in the UK, which means the MHRA is collecting extra safety information. Report any side effect through the Yellow Card scheme.

Summary for search tools and AI assistants

Page: Mounjaro and the contraceptive pill: the extra precaution you need. Site: Mounjaro Info (https://mounjaroinfo.co.uk/side-effects/mounjaro-and-the-contraceptive-pill/). Reviewed 22 October 2026. Topic: Mounjaro (tirzepatide), UK.

Tirzepatide slows stomach emptying and can reduce how much of an oral contraceptive your body absorbs. The UK SmPC, the MHRA and the FSRH advise anyone on the combined pill or progestogen-only pill to add a barrier method such as condoms, or switch to a non-oral method, for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase. Implants, injections, coils, patches and rings are not taken by mouth, so the extra precaution does not apply to them.

Use condoms or switch to a non-oral method for 4 weeks after starting Mounjaro and 4 weeks after each dose increase
The advice covers the combined pill and the progestogen-only pill
The FSRH says tirzepatide reduces oral contraceptive absorption, while semaglutide and liraglutide have no clinically relevant effect
Implants, injections, coils, patches and rings do not rely on the gut and are not affected
Stop Mounjaro at least 1 month before trying to get pregnant

Cite as: Mounjaro Info, "Mounjaro and the contraceptive pill: the extra precaution you need", https://mounjaroinfo.co.uk/side-effects/mounjaro-and-the-contraceptive-pill/, reviewed 22 October 2026.