Can you take warfarin while breastfeeding?
What LactMed says
The National Library of Medicine’s own summary, quoted in full. We do not write a verdict of our own on this question, and we do not compress theirs into a label.
Because of the very low milk levels with warfarin doses up to at least 12 mg daily, amounts ingested by the infant are small. No adverse reactions in breastfed infants have been reported from maternal warfarin use during lactation, even with a dose of 25 mg daily for 7 days. There is a consensus that maternal warfarin therapy during breastfeeding poses little risk to the breastfed infant. No special precautions are necessary.
Women’s postpartum warfarin dosage requirements may be increased by as much as two-fold compared to prepregnancy requirements. Whether breastfeeding contributes to the increased requirement is unclear.
Quoted from Warfarin — Drugs and Lactation Database (LactMed®), National Institute of Child Health and Human Development, revised May 15, 2024.
How much warfarin gets into breastmilk
Maternal Levels. Warfarin was not detected (<25 mcg/L) at 4 hours after a dose in the breastmilk of 13 mothers who were 3 to 12 days postpartum and anticoagulated with warfarin in doses of 2 to12 mg daily in one study.
Warfarin activity was also not detected in the milk of 2 anticoagulated women (warfarin dose unspecified).
Infant Levels. No warfarin activity was detected in the plasma of any of 7 infants in whom it was measured. Measures of anticoagulation were within normal limits in all infants tested.
What has been seen in breastfed infants
No decreases in vitamin K-dependent clotting factors or bleeding occurred in 2 infants who were breastfed for 56 and 131 days, respectively, during maternal anticoagulation with warfarin.
In one telephone follow-up study, mothers taking warfarin reported no adverse effects among 5 breastfed infants.
A mother had been taking warfarin 5 mg daily for the first 7 weeks postpartum for a pulmonary embolism. At this time, she began taking 25 mg daily by mistake and took this dose for 7 days. Upon presentation to the emergency room, her INR was greater than 10 (usual therapeutic maximum 3.5), her prothrombin time was greater than 100 seconds (normal up to 11.2 seconds), and her aPTT was 62.5 seconds (normal up to 32.7 seconds). She had been nearly exclusively breastfeeding her infant since birth. Her 8-week-old infant was healthy with an INR of 1.0, prothrombin time of 10.3 seconds, and a slightly elevated aPTT 33.8 seconds. However, 3 weeks previously, the infant's aPTT was 38.9 seconds, so the elevated aPTT was judged not to be caused by warfarin.
Effects on milk supply
Relevant published information was not found as of the revision date.
Frequently asked questions
Can you take warfarin while breastfeeding?
Because of the very low milk levels with warfarin doses up to at least 12 mg daily, amounts ingested by the infant are small. The full record is quoted on this page, and the decision is one to make with the person who prescribed it — LactMed itself states it is not a substitute for professional judgement.
Does warfarin pass into breastmilk?
LactMed's measured drug levels for warfarin are quoted in full on this page, under "How much gets into breastmilk".
Do I need to pump and dump after taking warfarin?
LactMed does not frame its records that way — it reports measured drug levels in milk and what has been observed in breastfed infants, which is what this page quotes. "Pump and dump" advice for a specific drug and dose should come from your clinician or a pharmacist, not from a general rule.
More on warfarin
LactMed states that the information it presents is not a substitute for professional judgement, and that you should consult your healthcare provider for breastfeeding advice related to your particular situation. Nothing on this page is medical advice.