Do Antibiotics Affect the Pill?
Reviewed by Usama Ali, MPharm (GPhC: 2224726). Last reviewed: July 2026.
For most antibiotics, no. Current UK guidance is that common antibiotics such as amoxicillin, penicillin, and trimethoprim do not reduce how well the contraceptive pill works. You do not need extra contraception while taking them. The exception is a small group of enzyme-inducing antibiotics, rifampicin and rifabutin, which do reduce effectiveness. And if an antibiotic or illness causes vomiting or severe diarrhoea, your pill may not be absorbed.
Do antibiotics affect the contraceptive pill?
For most antibiotics, no. Current UK guidance from the FSRH is that common antibiotics do not reduce how well the pill works, including amoxicillin, penicillin, trimethoprim, and doxycycline. Your combined pill or mini pill keeps working normally, unless you are vomiting or have severe diarrhoea.
Which antibiotics do affect the pill?
Only the enzyme-inducing antibiotics rifampicin and rifabutin, mainly used for tuberculosis and to prevent meningitis in close contacts. They speed up how your liver breaks down the pill's hormones, so there is less hormone to prevent pregnancy. If prescribed these, your prescriber will advise extra contraception or a method that is not affected, such as the injection, implant, or coil.
Why did the advice about antibiotics change?
For years people were told to use extra contraception with any antibiotic, based on caution rather than strong evidence. When reviewed, the evidence showed ordinary antibiotics do not affect hormone levels or increase pregnancy risk, so UK guidance was updated. Only enzyme-inducing antibiotics are now considered to reduce effectiveness.
What if antibiotics or the illness make you ill?
It is not the antibiotic interacting with the pill, but being unwell. If you vomit within 2 to 3 hours of taking your pill, or have severe diarrhoea, it may not be absorbed. Treat it like a missed pill and follow the rules for your pill type. For quick advice, use our missed pill tool.
What other medicines affect the pill?
The main medicines that reduce effectiveness are other enzyme-inducing drugs, not antibiotics: some epilepsy medicines (carbamazepine, phenytoin, topiramate), some HIV medicines, and the herbal remedy St John's Wort. Tell your pharmacist about any regular medication so they can check for interactions.
What should you do?
If you have a standard antibiotic, keep taking your pill as normal. If you have rifampicin or rifabutin, use extra contraception and speak to a pharmacist or prescriber. If unsure which antibiotic you have, or you have been sick, check with a pharmacist. With Contraception Direct you can book a free phone consultation and talk through your medicines.
Frequently asked questions
- Do antibiotics stop the pill working?
- For most antibiotics, no. Current UK guidance is that common antibiotics such as amoxicillin, penicillin, and trimethoprim do not reduce the effectiveness of the contraceptive pill. Only a small group of enzyme-inducing antibiotics (rifampicin and rifabutin) affect it.
- Does amoxicillin affect the pill?
- No. Amoxicillin and other common antibiotics do not make the pill less effective. You do not need to use extra contraception while taking them, unless the illness itself causes vomiting or severe diarrhoea.
- Do I need to use condoms while on antibiotics?
- Not for most antibiotics. You only need extra precautions if you are prescribed rifampicin or rifabutin, or if you are vomiting or have severe diarrhoea. If you are unsure which antibiotic you have, ask your pharmacist.
- Which antibiotics affect the contraceptive pill?
- Only enzyme-inducing antibiotics: rifampicin and rifabutin (used for tuberculosis and some other infections). These speed up how your body breaks down the pill's hormones, reducing its effectiveness. Your prescriber will usually flag this and advise extra contraception.
- Why did the advice about antibiotics and the pill change?
- For years, people were told to use condoms with any antibiotic. Research showed that most antibiotics do not affect hormonal contraception, so UK guidance was updated. Only enzyme-inducing antibiotics are now considered to reduce effectiveness.
- Does the pill still work if antibiotics make me sick?
- If an antibiotic (or the illness) makes you vomit within 2 to 3 hours of taking your pill, or you have severe diarrhoea, the pill may not be absorbed. Treat it like a missed pill and follow the missed pill guidance for your pill type.
- What other medicines affect the pill?
- Enzyme-inducing medicines can reduce the pill's effectiveness. These include some epilepsy medicines (such as carbamazepine and phenytoin), some HIV medicines, and the herbal remedy St John's Wort. Always tell your pharmacist what else you take.
References
- FSRH. Drug Interactions with Hormonal Contraception, 2022.
- NHS. Will antibiotics stop my contraception working?
- FSRH. Combined Hormonal Contraception Clinical Guideline, 2023 (amended 2024).