Quick answer

LactMed says vitamin K is naturally found in human milk, that a mother's supplement is typically not needed to meet the recommended intake, and that a mother's supplement alone is not an adequate or safe substitute for the vitamin K shot given to newborns. NIH sets no upper limit. Ask your doctor about your own supplement and your baby's shot.^1,2

Key facts

Vitamin K is naturally in human milk, and a mother's supplement is typically not needed to meet the recommended intake while breastfeeding, according to LactMed.¹
LactMed says exclusively breastfed infants are at higher risk of vitamin K deficiency bleeding, which can involve bleeding inside the skull and sometimes death.¹
LactMed says a mother's supplement is not an adequate or safe substitute for the vitamin K given directly to the newborn after birth, especially in preterm infants.¹
A mother's supplement of 5 mg a day raised milk vitamin K levels and the vitamin K status of breastfed infants who also received the newborn shot.¹
NIH's adequate intake for breastfeeding women is 90 mcg a day (75 mcg for teens), and it sets no upper limit.^2,3

What LactMed says about vitamin K and breast milk

LactMed, the National Library of Medicine's database for nursing mothers, says vitamin K is naturally found in human milk and that a maternal supplement is typically not needed to meet the recommended intake during lactation. It also notes that a supplement of 5 mg a day, a research amount many times the recommended intake, raised milk vitamin K and the vitamin K status of breastfed infants who had also had the newborn injection.¹

The entry then makes its central point. Exclusively breastfed infants are at higher risk of vitamin K deficiency bleeding, a condition that can involve intracranial bleeding and sometimes leads to infant death, because milk is a poor source of the vitamin. A mother's supplement alone is not an adequate or safe substitute for vitamin K given directly to the newborn after birth, especially for preterm infants.¹

The newborn shot and breastfed infants

LactMed describes a family in which three otherwise healthy brothers died of intracranial bleeding after being exclusively breastfed without the vitamin K dose at birth. A fourth brother, examined at 17 days, had abnormal clotting that returned to normal within 24 hours of a 1 mg vitamin K injection.¹

NIH's health professional sheet agrees on the setting. It says late deficiency bleeding occurs at 2 to 12 weeks, especially in exclusively breastfed infants because of the low vitamin K in breast milk, and that the American Academy of Pediatrics recommends a single intramuscular dose of 0.5 to 1 mg of vitamin K1 at birth. Ask your baby's pediatrician about the newborn shot.²

Little vitamin K crosses the placenta and breast milk is low in it, so newborns have little at birth. The American Academy of Pediatrics recommends a single shot of 0.5 to 1 mg of vitamin K1 for every newborn.²

What NIH lists for nursing mothers

NIH's adequate intake of vitamin K while breastfeeding is 75 mcg a day for teens and 90 mcg for women aged 19 and older. NIH sets no upper limit, because the expert panel found no adverse effects from vitamin K in food or supplements in people or animals. It says this does not hold for anyone taking warfarin.^2,3

No upper limit has been set for vitamin K, because of its low potential for harm: the expert panel that sets intakes found no reported adverse effects from vitamin K in food or supplements in people or animals. This does not apply to anyone taking warfarin or a similar blood thinner.^2,3

Who should ask their doctor

Ask your doctor before taking a vitamin K supplement while nursing if you take warfarin or a related blood thinner, since NIH says a sudden change in vitamin K can cause bleeding or clots. Ask your baby's doctor about the newborn dose if it was missed or declined, and about any vitamin K product given to the baby. Also ask if you have a condition that limits fat absorption.^1,3

Questions people ask

Is vitamin K safe while breastfeeding?

NIH sets no upper limit, and LactMed says a mother's supplement is typically not needed to meet the recommended intake. LactMed also says a mother's supplement is not a substitute for the newborn vitamin K dose.^1,2

Is a vitamin K supplement okay while breastfeeding?

LactMed says milk vitamin K rose with 5 mg a day, a research amount, and that a supplement is typically not needed. The sources checked do not give a routine supplement amount, so ask your doctor.¹

What blood thinners are safe while breastfeeding?

LactMed has separate entries for individual blood thinners, including warfarin. Its warfarin entry says milk levels are very low, no adverse reactions in breastfed infants have been reported, and no special precautions are necessary. Ask your doctor about yours.⁴

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.