To confirm whether vitamin K deficiency is diagnosed, a comprehensive judgment is made from three aspects: history, physical examination and laboratory tests: 1. Ask the patient whether there are relevant clinical manifestations of bleeding, such as oral, nasal, gastrointestinal and subcutaneous bleeding, if there is it should be considered more likely that vitamin K deficiency causes coagulation dysfunction. 2. Vitamin K deficiency requires a relevant physical examination, mainly to check whether the patient’s nasal cavity, oral cavity, groin, neck and subcutaneous bleeding are characteristic. 3. Applying corresponding laboratory tests, serum vitamin K concentration, tests for coagulation, decarboxylated serum vitamin K-dependent protein and urinary gamma-glutamate can be considered, and the presence of vitamin K deficiency can be determined by the testing of these four indicators.