Brodifacoum is a highly potent and long-acting anticoagulant rodenticide (LAAR). LAAR poisoning possibly leads to long term bleeding problems and needs vitamin K1 treatment for several months. Due to economic concern, tablet preparation of vitamin K1 was not available in most of the countries, including Taiwan. In literature, few reports had pointed out that injectable form of vitamin K could be used orally in patients on anticoagulant therapy with supratherapeutic state. Here, we reported a family with 3 members suffering from brodifacoum poisoning with severe coagulopathy needed to prolong hospitalization for intravenous vitamin K1 therapy, and successfully managed with injectable formula orally for about 5 months. Oral administration of injectable vitamin K1 might be a suitable substitute for intravenous route in long-term treatment for LAAR poisonings.