Breastfeeding While Taking Antibiotics: Is It Safe?

Why do antibiotics reach breast milk at all?

All medications that enter your bloodstream can, to some degree, pass into breast milk. The amount that reaches your baby depends on the drug's molecular size, fat solubility, protein binding, and elimination half-life. For most antibiotics, the concentration in breast milk is a small fraction of the therapeutic dose a clinician would prescribe directly for an infant. The authoritative reference for checking any specific drug is the NIH Drugs and Lactation Database (LactMed), which is free, peer-reviewed, and continuously updated 1Ref 1National Library of Medicine, National Institutes of Health (2024).Drugs and Lactation Database (LactMed®).Authoritative NIH/NLM database for checking drug safety during lactation; covers antibiotic transfer into breast milk, infant exposure levels, and safer alternatives.

Which antibiotics are generally considered safe while nursing?

The following classes are widely used in nursing mothers without concern for healthy, full-term infants [1, 2]:

• Penicillins (amoxicillin, amoxicillin-clavulanate, ampicillin, dicloxacillin) — among the most studied; transfer into milk is low
• Cephalosporins (cephalexin, cefazolin, cefuroxime) — similarly low transfer; commonly used for mastitis and skin infections
• Azithromycin — widely used for respiratory infections; low infant dose via milk
• Metronidazole — considered compatible for short courses; some providers advise a brief waiting window after each dose at high doses
• Nitrofurantoin — used for urinary tract infections; generally compatible except in the first month of life or in infants with certain enzyme deficiencies

This list is a general reference, not a complete guide. Your baby's age, health status, and the specific indication all affect the decision.

Which antibiotics call for extra caution or avoidance?

A small number of antibiotics carry enough concern that alternative choices are often preferred 1Ref 1National Library of Medicine, National Institutes of Health (2024).Drugs and Lactation Database (LactMed®).Authoritative NIH/NLM database for checking drug safety during lactation; covers antibiotic transfer into breast milk, infant exposure levels, and safer alternatives:

• Sulfonamides (sulfamethoxazole in TMP-SMX) — generally avoided in the first four to six weeks of life because of a theoretical risk of worsening jaundice in newborns
• Tetracyclines — typically avoided for courses longer than a few weeks because of the potential to affect bone and tooth development in infants; a short course poses less risk
• Chloramphenicol — rarely used in the US, but avoided during lactation due to risk of bone marrow effects in nursing infants
• Fluoroquinolones (ciprofloxacin, levofloxacin) — classified as compatible in many references for short courses, but some guidelines recommend alternatives when available

If you have been prescribed one of these, ask your prescriber whether an equally effective alternative is available.

What side effects might my baby have?

Even with antibiotics that are considered safe, small amounts reach your baby's gut and can occasionally:

• Alter the baby's intestinal flora, sometimes causing loose stools or fussiness
• Produce a rash in infants with a penicillin sensitivity (rare, but worth noting if you have a family history)

These effects are usually mild and resolve when the antibiotic course ends. If your baby develops a rash, unusual irritability, or significant feeding changes while you are on an antibiotic, contact your pediatrician.

Should I pump and discard milk when taking an antibiotic?

For most antibiotics, pumping and discarding is not necessary and not recommended 1Ref 1National Library of Medicine, National Institutes of Health (2024).Drugs and Lactation Database (LactMed®).Authoritative NIH/NLM database for checking drug safety during lactation; covers antibiotic transfer into breast milk, infant exposure levels, and safer alternatives. Doing so unnecessarily means your baby receives formula instead of breast milk with no safety benefit. The main exceptions are situations where your clinician specifically advises it based on the drug's profile. If you do pump and discard during a brief window, maintain your pumping schedule so your supply is not affected.

How to tell your prescriber — and who else to ask

Always mention you are breastfeeding at the start of any medical appointment and when picking up a prescription. Pharmacists are an excellent resource: they can consult LactMed or similar references on the spot and advise whether a switch to a safer alternative is warranted 1Ref 1National Library of Medicine, National Institutes of Health (2024).Drugs and Lactation Database (LactMed®).Authoritative NIH/NLM database for checking drug safety during lactation; covers antibiotic transfer into breast milk, infant exposure levels, and safer alternatives.

You generally do not need to stop breastfeeding to treat a common infection. For most prescriptions, continuing to nurse is both safe and beneficial for your baby 2Ref 2Meek JY, Noble L; Section on Breastfeeding, American Academy of Pediatrics (2022).Policy Statement: Breastfeeding and the Use of Human Milk.AAP policy on breastfeeding continuation during maternal illness and medication use, supporting that most antibiotic courses are compatible with nursing. A Gale clinician can review your antibiotic prescription and help you understand whether it is compatible with nursing, or refer you to a lactation consultant for specialized support.