All newborns need extra phylloquinone (vitamin K1; K1) to prevent vitamin K deficiency bleeding (VKDB). In preterm babies, the main sources are from prophylactic K1 given at birth and thereafter intake from parenteral and/or enteral feeding. Preterm babies are at risk of late-onset VKDB if ongoing K1 supplementation is inadequate. For extremely preterm infants fed an exclusive human milk diet (EHMD), the low K1 content of human milk may predispose them to vitamin K deficiency. Human milk fortification with either bovine milk-derived fortifier or human milk-based fortifier (HMF) made from pooled donor milk is a widely utilized strategy to improve the micronutrient and growth status of preterm infants. However, the K1 content of HMF is markedly lower than that of bovine-based preparations. We present an unusual case of late-onset VDKB in an extremely preterm infant who received an EHMD and HMF and quantify total K1 intake prior to the bleeding.