I just wanted to take a few moments to write this post following some of the conversations I’ve had in clinic recently — particularly around weight loss injections such as Mounjaro, Wegovy, and Saxenda, and how these can impact your contraception.
This might not be the most glamorous or exciting topic, but it’s hugely important. I know that many of you are doing amazing things for your health, taking control of your weight, blood sugars, or just generally feeling better in your body. But with that, we must also make sure we’re protecting your fertility, respecting your body’s hormonal balance, and not getting any surprises along the way (i.e. unexpected pregnancies!).
So, here’s a breakdown — simple, clear, and written from me to you — about what you really need to know if you’re using or thinking about using GLP-1 agonist medications like tirzepatide (Mounjaro) or semaglutide (Ozempic, Wegovy) alongside any form of contraception.
So, What Are GLP-1 Agonists?
Let’s start with the basics.
GLP-1 agonists are a class of medication that includes the likes of Mounjaro, Ozempic, Wegovy, Saxenda, Trulicity, and others. They work by mimicking a hormone called GLP-1, which helps regulate your appetite, improve insulin sensitivity, and — most relevant to our conversation today — slow down how quickly your stomach empties after eating.
This slowing down of the digestive process is brilliant for helping you feel full and helping with weight loss. But (and here’s the key part), it can also affect how well oral medications are absorbed — and yes, that includes the contraceptive pill.
The Pill and Mounjaro: What’s the Deal?
Now, this is where it gets a bit more specific.
If you’re using tirzepatide (Mounjaro), the current guidance is very clear: use extra contraception — such as condoms — for at least 4 weeks after starting the injection and after each time you increase the dose.
Why? Because tirzepatide may reduce how well your pill is absorbed, due to that delay in stomach emptying I mentioned earlier. And if your pill isn’t absorbed properly, it may not prevent pregnancy as effectively.
It’s not that it won’t work at all — but we don’t want to take chances. A missed pill or reduced absorption isn’t something to gamble with. Especially if you’re not planning for a baby right now.
What About the Other GLP-1 Medications?
Good news for those using semaglutide (Ozempic, Wegovy), liraglutide (Saxenda, Victoza), or exenatide (Bydureon) — these don’t appear to have the same effect on pill absorption.
There’s currently no evidence that these reduce the effectiveness of oral contraception. So if you’re on one of those, you should be fine — though I always recommend having a chat with your healthcare provider about your specific circumstances.
That said, if you’re switching from one of these medications to Mounjaro, then yes — same advice applies. You’ll need to use a backup method for a while.
What If You’re Feeling Sick?
This one comes up a lot in clinic — because unfortunately, side effects like nausea, vomiting, and diarrhoea are common when starting GLP-1 meds.
And these symptoms can directly affect how well your pill works too.
If you vomit within 3 hours of taking your pill, or have severe diarrhoea for more than 24 hours, then your pill may not be fully absorbed. In that case, you should follow the standard missed pill guidance — and again, use a backup method like condoms until you’re back on track.
Honestly, I see so many women unsure about what to do in these situations — so I recommend bookmarking or saving a link to a “missed pill calculator” online (I’ll include one below). It takes the guesswork out of it.
Non-Oral Contraception? No Problem.
Here’s the reassuring bit.
If you’re using a non-oral method of contraception — like the coil (IUD), the implant, the contraceptive injection, the vaginal ring, or the patch — then GLP-1 medications will not affect these methods.
These contraceptives bypass the digestive system altogether, so there’s no risk of interference with absorption, no matter how delayed your gastric emptying is.
So, if you’re on Mounjaro or any GLP-1 med and want peace of mind — or you’re experiencing persistent GI side effects — a non-oral contraceptive might be the best option for you.
Switching Between Weight Loss Injections? Be Careful
If you’re making the move from Ozempic or Saxenda over to Mounjaro, please remember: that changes the rules.
Even if you didn’t need to worry about contraception before, once you start tirzepatide, you need to go back to the 4-week rule with extra protection.
Transitions between medications are when many women get caught out — especially if you think “Oh, I’ve been fine on Wegovy, so Mounjaro should be the same.” But they’re not identical, and the body handles them differently.
This is one of those classic “better safe than sorry” scenarios.
What About Emergency Contraception?
This one’s important — especially if you’re reading this after the fact.
There isn’t yet enough research to say whether oral emergency contraception (like Levonelle or EllaOne) is impacted by GLP-1 meds, particularly if you’ve had vomiting or diarrhoea.
So, to be on the safe side, the most effective option is the copper coil (IUD). It can be fitted up to 5 days after unprotected sex, and it’s not affected by anything going on in your gut.
If you need emergency contraception, always tell your doctor, nurse, or pharmacist if you’re on GLP-1 medication. It could make a difference to what they recommend.
Thinking About Pregnancy?
This one’s crucial.
If you’re planning a pregnancy, you’ll need to stop your GLP-1 medication well in advance. These drugs are not safe to use during pregnancy, and you shouldn’t be on them while trying to conceive either.
Here’s the basic guidance:
- Tirzepatide (Mounjaro): Stop at least 1 month before trying
- Semaglutide (Ozempic/Wegovy): Stop at least 2 months before trying
- Exenatide (Bydureon): Stop 12 weeks before trying
These “washout” periods are essential to ensure the medication is out of your system before pregnancy begins. Again — talk to your GP, nurse, or specialist about this if it’s on your radar.
A Few Final Thoughts, From Me to You
I know this was a lot of information, and I hope I haven’t overwhelmed you. But if there’s one thing I’ve learned from years of practice, it’s that we make the best decisions when we’re informed.
These medications — Mounjaro, Ozempic, and the rest — are incredible tools. They are changing lives, helping with weight loss, blood sugar control, and improving health across the board. But they’re also powerful medications, and we must respect that.
If you’re on the contraceptive pill and thinking about starting (or have already started) any GLP-1 treatment, especially Mounjaro, please:
- Use condoms for the first 4 weeks, and again after any dose changes.
- Switch to non-oral contraception if you’re regularly unwell or prefer the ease.
- Speak to a healthcare professional if you’re unsure, or want to talk through options.
Your health, your hormones, your choices — they’re all connected. Let’s keep you safe, empowered, and in control.
Useful Resources:
- Missed Pill Calculator (The Lowdown)
- Faculty of Sexual and Reproductive Healthcare
- Your local GP, nurse, or sexual health clinic
Thank you for reading — and as always, if you’ve got questions, my door (virtual or otherwise) is always open.
- Extra protection needed: You should use condoms as backup for the first 4 weeks when starting Mounjaro or increasing the dose — it might affect how well the pill works.
- Other GLP-1s (like Ozempic, Wegovy, Saxenda etc.) don’t seem to affect the pill in the same way.
- Got vomiting or diarrhoea? That can lower the pill’s effectiveness too. If you’re sick within 3 hours of taking it, or have bad diarrhoea for over 24 hours, follow missed pill advice and use backup contraception (like condoms).
- Coil, implant, injection, patch, or ring? These are not affected by Mounjaro or any GLP-1 meds — no extra precautions needed.
- Switching to Mounjaro from another GLP-1? Same deal — backup contraception needed for 4 weeks.
- Emergency contraception? The coil is the most reliable if you’re on GLP-1s, especially if you’ve been unwell.
- Planning pregnancy? GLP-1s aren’t safe in pregnancy. For Mounjaro, you need to stop it at least 1 month before trying to conceive.