WeightGoneMounjaro, contraception and pregnancy: what you need to know
Medically reviewed by Muhammad Adnan, GPhC-registered Superintendent Pharmacist · Last updated June 2026
Mounjaro (tirzepatide) can affect how well the contraceptive pill works, and it should not be used when you're pregnant, trying to conceive, or breastfeeding. None of this means you can't use Mounjaro — it just means a little planning around contraception and pregnancy keeps you safe. Here's the clear, UK-based guidance.
The short version
- On the pill? Add condoms — or switch to a non-oral method — for 4 weeks after starting Mounjaro and for 4 weeks after every dose increase.
- Planning a baby? Stop Mounjaro at least 1 month before you start trying to conceive.
- Pregnant or breastfeeding? Mounjaro isn't for use during pregnancy or breastfeeding — stop and speak to us or your GP.
Why Mounjaro can affect the pill
Mounjaro slows down how quickly your stomach empties. That's part of how it helps you feel full — but it can also slow down how a swallowed tablet, like the contraceptive pill, is absorbed. This can make the pill less reliable for a short window. The effect is largest after your first dose and after each increase in dose, and it eases off as your body settles.
Methods that aren't swallowed are not affected — so the implant, the coil (IUD or IUS), the contraceptive injection, the patch and the vaginal ring all keep working normally.
What to do about contraception
If you're overweight or living with obesity and you take an oral contraceptive, UK guidance is to either:
- Switch to a non-oral method (implant, coil, injection, patch or ring), or
- Add a barrier method such as condoms for 4 weeks after you start Mounjaro and for 4 weeks after each dose increase.
If you're ever unsure whether you're covered, use condoms and ask us or your GP — it's always better to double up than to take a chance.
Losing weight can make you more fertile
This catches a lot of people out. Losing weight can restart regular ovulation and improve fertility — especially if you have PCOS. So even if you've found it hard to get pregnant in the past, it can become easier on treatment. If a pregnancy wouldn't be right for you now, use reliable contraception throughout — don't assume you're not at risk.
If you're planning a baby
Mounjaro should be stopped at least 1 month before you start trying to conceive, because it takes several weeks to clear from your body. (Some manufacturer and overseas guidance suggests leaving a little longer — up to around 2 months — so confirm the right timing with your prescriber.)
When you're planning a pregnancy, it's also a good time to start taking folic acid and to have a chat with us or your GP about a healthy approach to weight before and during pregnancy.
If you become pregnant unexpectedly
Stop taking Mounjaro straight away and contact us, your GP or your midwife for advice. Mounjaro is not known to be safe in pregnancy. Try not to panic — the important thing is simply to stop and get advice promptly so your care can be reviewed.
Breastfeeding
Mounjaro isn't recommended while you're breastfeeding. If you're breastfeeding or planning to, talk to your prescriber so you can plan the timing and discuss any alternatives.
How we handle this at WeightGone
Because we see you face-to-face and review you at least once a month, we'll ask about your contraception at your first consultation and check in around every dose increase — exactly when the extra care matters most. If you're thinking about a pregnancy, tell us early and we'll plan a safe way to come off treatment. See whether treatment is right for you, or read our who should not take it page.
Frequently asked questions
Does Mounjaro stop the contraceptive pill from working?+
It can make the pill less reliable — mainly in the first few weeks and after a dose increase. Mounjaro slows down how quickly your stomach empties, which can affect how well the pill is absorbed. The effect is largest after your very first dose and after each increase in dose, then it settles. If you take the pill, use a backup method during those times.
How long do I need to use extra contraception on Mounjaro?+
If you take an oral contraceptive (the pill) and are overweight or living with obesity, use a barrier method such as condoms — or switch to a non-oral method — for 4 weeks after you start Mounjaro and for 4 weeks after every dose increase. Non-oral methods don't need a backup.
Which contraception works best with Mounjaro?+
Methods that aren't swallowed aren't affected by Mounjaro's effect on the stomach — these include the implant, the coil (IUD/IUS), the contraceptive injection, the patch and the vaginal ring. If you'd rather stay on the pill, that's fine, but add condoms during the 4-week windows after starting and after each dose increase.
How long before trying for a baby should I stop Mounjaro?+
UK prescribing guidance advises stopping Mounjaro at least 1 month before you start trying to conceive, because the medicine takes several weeks to fully clear from your body. Some manufacturer and overseas guidance suggests leaving longer (up to about 2 months), so confirm the right timing for you with your prescriber. It's also a good time to start folic acid.
I think I'm pregnant, or fell pregnant while on Mounjaro — what should I do?+
Stop taking Mounjaro straight away and contact us, your GP or your midwife for advice. Mounjaro is not known to be safe in pregnancy, so it shouldn't be used while you're expecting. Try not to panic — just get advice promptly so your care can be reviewed.
Can I use Mounjaro while breastfeeding?+
Mounjaro isn't recommended while you're breastfeeding. If you're breastfeeding or planning to, speak to your prescriber so you can talk through the timing and any alternatives.
Not sure if it's right for you?
Have an honest, no-pressure chat with a GPhC-registered pharmacist in Timperley.
Sources
- Mounjaro (tirzepatide) — Patient Information Leaflet (emc / MHRA)
- Mounjaro (tirzepatide) — Summary of Product Characteristics, section 4.6 (emc / MHRA)
- FSRH / CEU — GLP-1 agonists and contraception (patient information)
- MHRA — prescription weight-loss medicines: information for the public
- NHS — Medicines A to Z
This page is for general information and isn't a substitute for personal medical advice. Your pharmacist will assess what's right for you at a face-to-face consultation.