When determining whether a child’s bleeding is caused by vitamin K deficiency, physicians often make a diagnosis based on the infant’s feeding status, clinical presentation, plus the necessary laboratory tests. Ancillary tests The main tests needed include coagulation tests, including prothrombin time (PT), activated partial thromboplastin time (APTT), leukotocin partial thromboplastin time (KPTT), prothrombin time (TT), etc. Fibrinogen and platelets can also be measured. If vitamin K deficiency is present, the activity of vitamin K-dependent factors (factors II, VII, IX, and X) decreases, PT, APTT, and KPTT are prolonged, but TT, fibrinogen, and platelet counts are normal. In addition, hospitals that have the conditions can also determine vitamin K deficiency-inducing protein and vitamin K levels to clarify the diagnosis. The main differentiation point is that the blood vomited by a child with pharyngeal syndrome is the mother’s blood swallowed, and the Apt test can be performed to determine if it is the mother’s blood. Gastrointestinal bleeding can also be seen in stress ulcers, mostly in neonatal asphyxia, infection, intestinal perforation, and necrotizing small bowel colitis. In children with congenital thrombocytopenic purpura, bleeding is accompanied by thrombocytopenia; in diffuse intravascular coagulation, in addition to prolonged PT and TT, fibrinogen and platelets are also reduced. Therefore, it is important to differentiate from bleeding with vitamin K deficiency.