Do antibiotics affect birth control?
This is one of the most common medication questions — and the answer is more specific than the popular belief. Here's what the evidence actually says.
The common myth
Many people believe all antibiotics make birth control pills fail. For most common antibiotics (like amoxicillin), current evidence does not show a meaningful reduction in birth control effectiveness.
The real exception
The antibiotic that clearly matters is rifampin (and related "rifamycin" drugs, used for tuberculosis and some other infections). Rifampin speeds up how the body clears hormones and can make hormonal birth control less effective.
What to do
- If you're prescribed rifampin/rifabutin, ask about backup contraception.
- Being sick with vomiting or diarrhea can reduce absorption of the pill — use backup if that happens.
- When unsure, use a backup method and ask your pharmacist.
Bottom line: Most antibiotics don't require backup contraception, but rifampin does. Your pharmacist can confirm for your specific antibiotic.
Check your own medicines free
See how your prescriptions, supplements, and food may interact — organized by the part of the body they affect.
Open the medication tool →Important: This article is educational and not medical advice. It does not replace your pharmacist or prescriber. Always confirm decisions about your medicines with a qualified professional, and call your local emergency number for emergencies. In the U.S., Poison Control is 1-800-222-1222.