If you’re using Mounjaro and you’re on the pill, there’s something you need to know: Mounjaro (Tirzepatide) can make your oral contraception less effective.
This often catches people off guard. You might have used Wegovy before without any issues, but Mounjaro works slightly differently – and that difference matters when it comes to contraception.
If you’re taking birth control pills – either the combined pill or the progestogen-only pill (mini-pill) – Mounjaro can reduce their effectiveness.
Studies on oral contraceptives found that tirzepatide reduced peak absorption levels by up to 66%.
Mounjaro slows gastric emptying, which means oral medications like the pill spend more time in your stomach than they do in your intestines. Because the pill is absorbed in your intestines, not your stomach, it won’t absorb as well as it should, and your contraception becomes less reliable.
The risk is highest when you first start Mounjaro or when you increase your dose – which is why you need to take extra precautions during these times.
If you’re taking the pill and using Mounjaro, you have two options:
Option 1: Use a barrier method of contraception alongside your pill
Continue taking your pill as normal, but also use condoms or another barrier method:
Option 2: Switch to a non-oral form of contraception
Methods like the IUD (coil), contraceptive implant, injection, patch, or vaginal ring aren’t affected by Mounjaro because they don’t rely on absorption through your stomach.
If you’ve been taking a GLP-1 agonist like Wegovy, Ozempic, or Saxenda without any issues with your pill, you might be wondering why Mounjaro is different.
The current evidence shows that other GLP-1 agonists don’t have the same effect on pill absorption through delayed gastric emptying. This includes:
These medications work slightly differently to Mounjaro. While they’re all GLP-1 agonists used for type 2 diabetes and weight management, Mounjaro is also a GIP receptor agonist – a dual-action medication. This difference in how it works appears to have a stronger effect on gastric emptying, which is why it can interfere with contraception when other GLP-1s don’t.
However, these medications can also cause vomiting and diarrhoea, which can affect how well the pill works. The key difference is that with Mounjaro, you need extra precautions even when you’re not experiencing side effects.
If you’ve been using Wegovy or Ozempic and switch to Mounjaro, you’ll need to start using backup contraception for 4 weeks, even if you never needed to before.
Switching from Mounjaro to Wegovy means you can stop the extra precautions once you’ve stopped taking Mounjaro, though it’s worth discussing the timing with your prescriber.
The good news is that if you’re using a non-oral method of hormonal contraception, you don’t need to take any additional precautions when using Mounjaro. These methods aren’t affected by delayed gastric emptying because they don’t rely on absorption through your stomach.
Safe to use alongside Mounjaro without extra precautions:
These methods deliver hormones directly into your bloodstream or work locally, so they bypass your digestive system entirely. For many people using Mounjaro, switching to one of these methods is simpler than remembering to use condoms for 4 weeks after every dose increase.
Mounjaro commonly causes gastrointestinal side effects, particularly nausea, vomiting, and diarrhoea. These are usually most intense when you first start treatment or increase your dose, which is also when taking the contraceptive pill is already at a higher risk of being less effective.
If you experience vomiting or severe diarrhoea while taking the pill, this can further reduce how well your contraception works.
If you vomit within 3 hours of taking your pill, follow the guidance for missed pills that comes with your contraceptive pill, which typically involves:
Severe diarrhoea that lasts more than 24 hours can also affect how well your pill is absorbed. If this happens, follow the same missed pill guidance and use barrier contraception until you’ve taken your pill correctly for the required number of days.
If you’re experiencing persistent nausea, vomiting, or diarrhoea, it’s worth speaking with your prescriber. They might suggest adjusting your Mounjaro dose or timing, or you might want to consider switching to a non-oral contraceptive method that won’t be affected by these symptoms.
If you’ve had unprotected sex or think your contraception might have failed while taking Mounjaro, you need emergency contraception. The problem is we don’t yet have clear evidence about whether oral emergency birth control methods (the morning-after pill) are affected by Mounjaro in the same way that regular oral contraception is.
The copper IUD (coil) is the most effective form of emergency contraception, and it’s not affected by Mounjaro or any gastrointestinal symptoms. It can be fitted up to 5 days after unprotected sex and is more than 99% effective at preventing pregnancy.
If you’re already planning to use a non-oral contraceptive method going forward, having a copper IUD fitted as emergency contraception gives you ongoing protection that won’t be affected by Mounjaro.
Oral emergency contraception (like ellaOne or Levonelle) is still an option, but because Mounjaro may affect how oral medications are absorbed, you should inform the pharmacist or doctor that you’re taking Mounjaro when you request it. They can advise you on the best option for your situation.
If you’re staying on the pill while using Mounjaro, you need to know exactly when you need to use barrier contraception as backup.
| Situation | How long to use barrier contraception |
| When you first start Mounjaro | For 4 weeks after your first dose, even if you’re taking your pill as normal |
| After every dose increase | For 4 weeks after each dose increase (applies to all increases: 2.5mg to 5mg, 5mg to 7.5mg, and beyond) |
| During vomiting or severe diarrhoea | If you vomit within 3 hours of taking your pill, or have severe diarrhoea lasting more than 24 hours, follow the missed pill guidance for your specific contraceptive and use barrier methods until your protection is re-established |
| When switching from another GLP-1 to Mounjaro | For 4 weeks from your first Mounjaro dose, even if you never needed extra precautions with Wegovy, Ozempic, or Saxenda |
Barrier contraception means condoms (male or female), diaphragms or cervical caps. For condoms to be effective:
If you’re finding it difficult to remember or consistently use barrier methods during these periods, switching to a non-oral contraceptive method might be a more practical long-term solution.
Click2Pharmacy offers private prescriptions for weight loss injections, including Mounjaro, as well as oral contraceptive pills and emergency contraception.
Whether you’re starting Mounjaro and need to review your contraception, or you’re looking to switch to a more convenient method that won’t be affected by your weight loss treatment, Click2Pharmacy can help.
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