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Pregnancy & contraception

Do antibiotics make your birth control pill less effective?

Most antibiotics do not reduce the effectiveness of hormonal birth control, but some medicines can. Here is how to get a safe answer for your prescription and method.

5 min read

Short answer

Most commonly prescribed antibiotics do not make hormonal birth control less effective. A small number of medicines can interact with hormonal contraception, and vomiting or severe diarrhoea can also affect how well an oral pill is absorbed.

The safest answer is to ask the pharmacist who dispenses your prescription or the clinician who prescribed it. Tell them the exact name of your contraceptive, because pills, patches, rings, implants and injections do not all work in the same way.

Why the myth is so common

Many people are told that every antibiotic cancels out the pill. Current guidance does not support that as a general rule. The CDC’s medical eligibility information says that most broad-spectrum antibiotics do not affect the effectiveness of combined oral contraceptives, the patch or the ring.

Some drugs, including certain rifamycin antibiotics, are different. They can reduce the levels of hormones used by some contraceptive methods. The right response depends on the specific medicine and contraceptive, not on the word “antibiotic” alone.

Illness can matter too

If you take an oral contraceptive and have vomiting or severe diarrhoea, the issue may be absorption rather than a drug interaction. Your packet leaflet should explain what to do after a missed or not-absorbed pill. A pharmacist can also help you interpret it.

Do not stop an antibiotic or a contraceptive by yourself because of an internet warning. Treating an infection properly matters. A clinician can help you use any additional protection that is appropriate for your exact situation.

If you have already had sex

If you are concerned that a medicine or illness may have affected your contraception and you have had sex, seek advice promptly. The timing and details decide whether emergency contraception or a pregnancy test plan may be relevant.

The bottom line

Most antibiotics are not a reason to assume the pill has failed. Check the exact drug and method with a pharmacist or clinician, and ask promptly if you have had sex during a possible interaction.

Sources and further reading