Vitamin K
Vitamin & mineralAlso called · 8 names▾▴
Vitamin K1, K1, phylloquinone, phytonadione, Vitamin K2, K2, menaquinone, Vitamin K supplement
Vitamin and mineral supplement
Herbs and supplements are not FDA-approved before sale. About these sources
- Capsule/tablet
- Softgel
- Food / spice
Research strength: 3 / 5
MotherToBaby says vitamin K at the adequate intake is not expected to increase the chance of miscarriage or birth defects. NIH ODS and MotherToBaby list an adequate intake of 90 mcg per day for pregnant adults and 75 mcg for ages 14 to 18; most people get enough from food, although diet, medicines, or health conditions can affect levels. MotherToBaby describes case reports after maternal deficiency with skull or brain findings, but says the reports cannot show that deficiency caused them. NIH ODS has not set an upper intake limit, and a 2018 review found evidence on milligram-dose pregnancy trials very uncertain, including no significant reduction in newborn bleeding. Ask your provider about your situation.
Last reviewed: 2026-10-16
Research strength: 3 / 5
MotherToBaby says vitamin K at the adequate intake is not expected to increase the chance of preterm delivery or low birth weight. NIH ODS and MotherToBaby list an adequate intake of 90 mcg per day for pregnant adults and 75 mcg for ages 14 to 18; most people get enough from food, although diet, medicines, or health conditions can affect levels. MotherToBaby describes case reports after maternal deficiency with skull or brain findings, but says the reports cannot show that deficiency caused them. NIH ODS has not set an upper intake limit, and a 2018 review found evidence on milligram-dose pregnancy trials very uncertain, including no significant reduction in newborn bleeding. Ask your provider about your situation.
Last reviewed: 2026-10-16
Research strength: 3 / 5
MotherToBaby says vitamin K at the adequate intake is not expected to increase the chance of other pregnancy problems, including preterm delivery or low birth weight. NIH ODS and MotherToBaby list an adequate intake of 90 mcg per day for pregnant adults and 75 mcg for ages 14 to 18. A 2018 review of antenatal supplement trials found no significant reduction in newborn bleeding and rated the evidence very low; this evidence concerns maternal supplementation during pregnancy, not the newborn vitamin K dose. Case reports after severe maternal deficiency do not establish that ordinary intake causes fetal findings. Ask your provider about your situation.
Last reviewed: 2026-10-16
Vitamin K — Breastfeeding
Research strength: 4 / 5
MotherToBaby and NIH ODS list an adequate intake of 90 mcg per day for breastfeeding adults and 75 mcg for ages 14 to 18. LactMed gives 75 mcg per day for maternal intake without an adult age qualifier, and the reviewed sources do not explain the difference. LactMed reports that 5 mg per day from the mother raised milk vitamin K and infant vitamin markers in small studies, but infants also received the newborn shot and bleeding outcomes were not tested. CDC says breast milk remains low even when mothers take supplements and says infants who receive the intramuscular newborn shot need no further supplementation. A 2026 review proposes ongoing infant doses, which differs from CDC guidance; that debate is about infant prevention, and maternal supplements alone do not replace the newborn dose. Ask your provider about your situation.
Last reviewed: 2026-10-16
Sources
- MotherToBaby: Vitamin KTeratology service
- LactMed: Vitamin KUS government
- NIH Office of Dietary Supplements: Vitamin K, Health Professional Fact SheetUS government
- CDC: Vitamin K and BreastfeedingUS government
- AAP: Vitamin K and the Newborn InfantUS government
- Greer et al., Improving the vitamin K status of breastfeeding infants with maternal vitamin K supplementsUS government
- Perrone et al., Late Vitamin K Deficiency Bleeding in Infancy: The Time to Ensure Effective PreventionUS government
Pregnancy
MotherToBaby says vitamin K at the adequate intake is not expected to increase miscarriage, birth defects, preterm delivery, or low birth weight. NIH ODS and MotherToBaby list an adequate intake of 90 mcg/day for pregnant adults and 75 mcg/day for ages 14-18; both say many people get enough from food, while diet, medicines, and health conditions can affect levels. The AIs apply to usual nutrient intake, not treatment of a measured deficiency or high-dose use. ODS has not set an upper intake limit for vitamin K. A 2018 systematic review included six trials and 21,493 women-newborns; most studies had high or unclear risk of bias. The pooled neonatal bleeding result was not significant (RR 1.16, 95% CI 0.59-2.29, P=0.67), and the review rated the evidence very low. Maternal bleeding and perinatal death were not reported. One small prenatal study gave 10 mg/day orally for two weeks to 74 participants and compared them with 186 controls; it measured newborn coagulation markers, not clinical bleeding, and its authors' suggestion that prenatal intake might replace newborn prophylaxis is not current CDC/AAP guidance. Maternal deficiency associated with severe malabsorption or hyperemesis is a separate clinical problem: Menger et al. described three infants of mothers with chronic malabsorption and stated that other vitamin deficiencies could not be excluded. A 2021 systematic review of hyperemesis-related deficiency summarized selected case reports and one cohort but could not estimate incidence. These deficiency reports are not evidence that usual dietary intake or routine-dose supplements cause fetal findings. Recent evidence includes a 2025 online cohort study (Mateu-Fabregat et al., n=1,080) associating higher dietary phylloquinone with some early-childhood development scores; it was observational and did not test supplements. Li et al. (2026, n=178) reported preliminary associations between serum vitamin K isoforms and pregnancy outcomes; the study excluded recent vitamin K2 supplement users and did not establish supplement effects. Larger prospective studies are needed.
Breastfeeding
MotherToBaby and NIH ODS list a lactation AI of 90 mcg/day for adults and 75 mcg/day for ages 14-18. LactMed states 75 mcg/day without an adult age qualifier; the reviewed pages do not explain the difference. LactMed says maternal supplementation with 5 mg/day increases milk vitamin K and can improve infant vitamin K status when infants also receive intramuscular vitamin K shortly after birth. Greer et al. (1991) gave one oral 20 mg dose to 11 lactating mothers and found milk levels rose; in a separate small longitudinal group, breastfed infants' plasma phylloquinone remained very low, and no overt deficiency occurred in that sample. Greer et al. (1997) studied 20 mothers during dose selection and 22 mother-infant pairs in a randomized, double-blind, placebo-controlled phase; 11 mothers received 5 mg/day. All infants received 1 mg intramuscular vitamin K at birth. Maternal supplementation raised milk and infant vitamin K biomarkers, but prothrombin times did not differ and clinical bleeding outcomes were not tested. These studies support milk transfer and biomarker effects, not replacing the newborn dose. CDC says breast milk is low in vitamin K even when mothers take supplements, recommends one intramuscular newborn dose within six hours after birth, and says infants who receive that shot do not need further supplementation. AAP policy identifies intramuscular prophylaxis as standard care. A 2026 secondary analysis of 48 breastfeeding women found adequate maternal serum phylloquinone, but vitamin K dietary intake data were unavailable and the study did not establish supplement effects. A 2026 review by Perrone et al. argues for continued infant prophylaxis, including 150 mcg/day orally for exclusively breastfed infants during the first three months. That proposal differs from CDC guidance and concerns infant prophylaxis, not maternal supplements. A 2026 infant case report described late vitamin K deficiency bleeding in a 2-month-old exclusively breastfed infant born at home without birth prophylaxis; it does not show harm from maternal supplementation.
Vitamin K includes phylloquinone (vitamin K1) and menaquinones (vitamin K2). NIH ODS identifies phylloquinone as the main dietary form and notes that vitamin K is found in foods and dietary supplements. MotherToBaby's fact sheet covers forms found in supplements, fortified foods, and naturally occurring foods. A prescribed phytonadione injection is a separate medicine form and route from the oral supplements and foods in the live item.
What was tested
Pregnancy evidence includes older antenatal supplementation trials, a systematic review of clinical outcomes, case reports involving severe maternal deficiency, and newer observational studies of dietary intake or serum vitamin K isoforms. The 2025/2026 dietary cohort did not test supplements; the 2026 isoform study excluded recent vitamin K2 supplement users. Lactation evidence includes small maternal-dose studies measuring milk levels and infant vitamin K biomarkers, with no clinical bleeding outcomes established. The 2026 cohort of 48 breastfeeding women lacked vitamin K dietary intake data. A 2026 infant prophylaxis review and infant case reports concern infant dosing and should not be read as evidence about maternal supplement effects.
Adequate intake for adults during breastfeeding
- Source A says
- NIH ODS and MotherToBaby list 90 mcg/day for breastfeeding adults and 75 mcg/day for ages 14-18. (NIH Office of Dietary Supplements: Vitamin K, Health Professional Fact Sheet, MotherToBaby: Vitamin K)
- Source B says
- LactMed states a recommended maternal dietary intake of 75 mcg/day during lactation without an adult age qualifier. (LactMed: Vitamin K)
- Why they differ
- NIH ODS and MotherToBaby show age-specific adequate intakes. LactMed gives 75 mcg/day in its lactation summary without describing an age band. The reviewed sources do not explain the discrepancy.
- What the evidence shows overall
- The NIH ODS and MotherToBaby pages support 90 mcg/day for adults and 75 mcg/day for ages 14-18. LactMed's unqualified 75 mcg/day statement should be shown as a source difference rather than silently reconciled. This does not establish a maternal supplement risk or change the compatibility rating.
Further infant vitamin K supplementation after the intramuscular birth dose
- Source A says
- CDC says infants who receive the intramuscular birth dose do not require further supplementation; AAP policy identifies intramuscular newborn prophylaxis as standard care. (CDC: Vitamin K and Breastfeeding, AAP: Vitamin K and the Newborn Infant)
- Source B says
- Perrone et al. (2026) argue for ongoing infant prophylaxis and describe 150 mcg/day oral vitamin K for exclusively breastfed infants during the first three months. (Perrone et al., Late Vitamin K Deficiency Bleeding in Infancy: The Time to Ensure Effective Prevention)
- Why they differ
- CDC states current US guidance. Perrone et al. is a review advocating broader infant-prevention practices based partly on observational biomarker findings. Its proposal is not a CDC or AAP guideline and does not concern maternal supplementation.
- What the evidence shows overall
- The disagreement is about continued infant prophylaxis after birth, not the mother's nutrient intake. The 2026 review is a proposal in a review article, while CDC guidance says no further infant supplement is needed after the intramuscular shot. Maternal supplements alone are not a substitute for the newborn dose.
- MotherToBaby says most people get enough vitamin K from food, while diet, medicines, or certain health conditions may mean that some people need a supplement. It advises discussing prescribed vitamin K with a healthcare provider before making changes. (MotherToBaby)
- NIH ODS says people taking warfarin and similar anticoagulants need to maintain a consistent vitamin K intake from food and supplements. (NIH Office of Dietary Supplements)
General research, not specific to pregnancy.
Vitamin K intake can matter for people taking vitamin K-antagonist medicines such as warfarin.
- NIH ODS says people taking warfarin and similar anticoagulants need to maintain consistent vitamin K intake because these medicines antagonize vitamin K activity. (NIH Office of Dietary Supplements: Vitamin K, Health Professional Fact Sheet)
- MotherToBaby: Vitamin KTeratology serviceSecondary
- LactMed: Vitamin KUS governmentSecondaryPage dated 2026-09-15
- NIH Office of Dietary Supplements: Vitamin K, Health Professional Fact SheetUS governmentSecondaryPage dated 2021-03-29Independent check
- CDC: Vitamin K and BreastfeedingUS governmentSecondaryPage dated 2025-09-23Independent check
- AAP: Vitamin K and the Newborn InfantUS governmentSecondaryIndependent check
- Greer et al., Vitamin K status of lactating mothers, human milk, and breast-feeding infantsUS governmentPrimaryIndependent check
- Greer et al., Improving the vitamin K status of breastfeeding infants with maternal vitamin K supplementsUS governmentPrimaryIndependent check
- Anai et al., Can prenatal vitamin K1 supplementation replace prophylaxis at birth?US governmentPrimaryIndependent check
- Shahrook et al., Vitamin K supplementation during pregnancy for improving outcomes: a systematic review and meta-analysisUS governmentPrimaryIndependent check
- Menger et al., Vitamin K deficiency embryopathy: a phenocopy of the warfarin embryopathy due to a disorder of embryonic vitamin K metabolismUS governmentPrimaryIndependent check
- Nijsten et al., Hyperemesis gravidarum and vitamin K deficiency: a systematic reviewPrimaryIndependent check
- Mateu-Fabregat et al., Maternal dietary phylloquinone intake and early childhood neurodevelopmentUS governmentPrimary
- Li et al., Associations between maternal circulating vitamin K isoforms and adverse pregnancy eventsUS governmentPrimary
- Ali et al., Vitamins A, D, E, and K Intakes, Status, and Breastmilk Concentrations in Breastfeeding Women in IrelandUS governmentPrimary
- Perrone et al., Late Vitamin K Deficiency Bleeding in Infancy: The Time to Ensure Effective PreventionUS governmentPrimary
- Perrone et al., Vitamin K Biochemistry and Pharmacokinetics: The Basis of Late Vitamin K Deficiency Intracranial Bleeding in Early InfancyUS governmentPrimary
- Ali et al., Late Vitamin K Deficiency Bleeding Presenting as Subacute Subdural Hemorrhage in an Exclusively Breastfed InfantUS governmentPrimary
Last reviewed 2026-10-16
Independent check 2026-10-16
Not yet clinician-reviewed
Ask your provider about your situation.