Medicines that can affect contraception

It's completely normal to wonder how your contraception might interact with any medication you're taking. Most medicines don't affect contraception, but there are some treatments that can make certain contraceptive methods less effective. This is because certain medicines might affect how hormones are absorbed, processed or broken down by the body.

The contraceptive pill is the method most commonly associated with medicine interactions, although other hormonal contraceptives can sometimes be affected too. If you’re unsure, it’s always best to check with a pharmacist or other healthcare professional – but we’ll cover some of the key facts and myths below.

Some medicines are known to interact with hormonal contraception. Examples might include certain:

• Epilepsy medicines
• HIV medications
• Tuberculosis treatments
• Medicated weight loss treatments
• St John's Wort (a herbal remedy used to treat moderate depression)
• Other medicines used for long-term medical conditions

The potential interaction depends on both the medication you're taking, and the type of contraception you're using. Everyone's circumstances are different, so it's best to seek medical advice to be sure.

If you're taking weight-loss medication and using oral contraception, it's important to be aware that some treatments may affect how well the contraceptive pill works.

Certain treatments like Mounjaro work by slowing down digestion, which can reduce the absorption of oral medicines, such as the contraceptive pill. Even if the weight loss treatment you're using doesn't work in this way, it could still cause side effects such as vomiting or diarrhoea, which may in turn reduce the effectiveness of your oral contraception.

If you're unsure about how your weight loss medication and contraceptive pill might be interacting, you can speak to a pharmacist or healthcare professional for advice.

Most antibiotics don't impact the effectiveness of the contraceptive pill, however, there are a small number of exceptions, and some antibiotics may require additional precautions.

If you're prescribed antibiotics and use hormonal contraception, it's always worth checking with your pharmacist on whether you should be taking any additional contraceptive precautions.

Whenever you're prescribed, recommended or planning to buy new medicine or supplements, it's always a good idea to mention if you're using hormonal contraception. Although most herbal products and supplements can be bought without a prescription, you might be surprised to learn that some of them can still affect hormonal contraception. A pharmacist can quickly check for any interactions and advise if:

• Additional contraception precautions are recommended
• An alternative medication might be more suitable
• Emergency contraception advice may be appropriate

This might be particularly relevant if you're exploring contraception after having a baby, or contraception during menopause, where you might be taking other medicines and supplements.

If you're unwell while using contraception, then it's not just medicine interactions that you need to think about. If you're sick (vomiting) or experiencing diarrhoea, then your body may not absorb oral contraception properly. This means that your pill might be less effective than usual.

If you find yourself in this situation and aren't sure what to do, then you can speak to a pharmacist or other healthcare professional for advice.