It depends on which type of contraception you’re using.
It’s now thought the only types of antibiotic that interact with hormonal contraception and make it less effective are rifampicin and rifabutin. These can be used to treat or prevent diseases including tuberculosis and meningitis.
When you take two or more medicines at the same time, the effects of one medicine can be altered by the other. This is known as an interaction. Some antibiotics can interact with some forms of hormonal contraception.
Hormonal contraception
There are several types of hormonal contraception, such as:
If you’re using hormonal contraception, it’s important to understand that some medicines may reduce its effectiveness. This includes some types of antibiotic. If this happens, to avoid getting pregnant you’ll need to use additional contraception, such as condoms, change to a different method of contraception or take your contraception in a different way. See Additional contraception.
If you’re not sure if your contraception is affected by other medicines, speak to your GP or pharmacist or call NHS Direct on 0845 4647.
Antibiotics
Rifampicin-like medicines are the only type of antibiotic that can make some kinds of hormonal contraception less effective. They include:
These types of medicine can increase the enzymes in your body. This is known as being 'enzyme-inducing', and can affect hormonal contraception.
Enzymes are proteins that control your body’s chemical reactions. Enzyme-inducing antibiotics speed up the processing of some contraceptive hormones and therefore reduce the levels of these hormones in your bloodstream. This makes the contraceptive less effective.
Apart from those mentioned above, all other antibiotics are not enzyme-inducing.
Additional contraception
If you’re going to take rifampicin or rifabutin for more than two months, you may want to consider starting, or changing to, a contraception method that’s not affected by these medicines. You should consider this if you’re currently using the:
- combined pill
- progestogen-only pill
- implant
- patch
- vaginal ring
Contraception methods that aren’t affected by rifampicin or rifabutin include:
If you’re taking rifampicin or rifabutin for less than two months and want to continue your same hormonal contraception, you must discuss this with your doctor. You may be asked to take this contraception in a different way from usual and use condoms as well. You will need to continue this for 28 days after finishing the antibiotics.
One option for women taking a short dose of rifampicin (for preventing meningitis, for example) is a single dose of the progestogen injection. The implant can stay in place while you're covered by the injection.
You and your doctor can get up-to-date guidance from the Faculty of Sexual and Reproductive Healthcare.
If you’re taking antibiotics other than rifampicin or rifabutin, you don’t normally need to use additional contraception.
However, if the antibiotics, or the illness they are treating, cause diarrhoea or vomiting, your oral hormonal contraception may be affected. For more information, see What if I’m on the pill and I’m sick or have diarrhoea?
Non-antibiotic drugs and hormonal contraception
Some other non-antibiotic medications are enzyme-inducing and can affect hormonal contraception. These include:
- some drugs used to treat epilepsy
- antiretroviral medicines used to treat HIV
- St John’s Wort (a herbal remedy)
Your GP or nurse may advise you to use an alternative or additional form of contraception while taking one of these medicines. You can find out more in Does the pill interact with other medicines?
