Continuous renal replacement therapy (CRRT) in neonates and children has recently been used to treat hyperammonemia and metabolic disorders. However, CRRT introduction in low-birth-weight neonates is still a challenge due to vascular access limitations, bleeding complications, and a lack of neonatal-specific devices. We present the case of a low-birth-weight neonate whose severe coagulopathy due to CRRT introduction with a red cell concentration-primed circuit was alleviated by priming the new circuit with blood from the current circuit. This male preterm infant (birth weight: 1,935 g) was admitted to the pediatric intensive care unit at two days old with metabolic acidosis and hyperammonemia, which required CRRT. Following CRRT introduction, he showed marked thrombocytopenia (platelet count: 305,000-59,000/μL) and coagulopathy (prothrombin time international normalized ratio (PT/INR) >10), necessitating platelet and fresh frozen plasma transfusions. Upon circuit exchange, we primed the new circuit with blood from the current circuit. This resulted in only a slight worsening of thrombocytopenia (platelet count: 56,000-32,000/μL) and almost no change in coagulation (PT/INR: 1.42-1.54). We also reviewed the literature regarding safe CRRT management in low-birth-weight neonates. Since there is no established method for the use of blood from the current circuit during circuit exchange, this should be addressed in future work.