Background: Inborn errors of metabolism (IEM) are a diverse collection of genetic abnormalities that are a significant source of illness and death in children.
Objectives: To determine the prevalence of IEM in newborns with suspected IEM and to diagnosis IEM as soon as feasible to reduce morbidity and death in ill neonates.
Subjects and methods: the study included 50 neonates were admitted to Minia University's Neonatal Intensive Care Unit (NICU) between January 2021 and January 2022 with sepsis-like symptoms (lethargy, hypoactivity, poor suckling, and poor crying), as well as convulsions, persistent metabolic acidosis, persistent vomiting, or a history of previous sib death from an unknown cause, or clinical deterioration in a previously healthy neonate. 
Result: Out of 50 neonates, eighteen patients (36%) were diagnosed as having IEM. Urea cycle defect was the commonest IEM diagnosed in 7 (14%) cases, followed by suspected organic academia in 4(8%) cases then MSUD in 2 (4%). TMS confirmed the diagnosis of IEM in 11 out of 18 patients diagnosed with IEM. The other seven cases that had IEM were diagnosed by using other clinical and laboratory investigation. 20 (40%) of the patients had a history of siblings' deaths, whereas 3 (6%) had no history of siblings' deaths (diagnosed with IEM).
Conclusions: IEM is a common cause of neonatal illness in the NICU. IEM studies should be performed regularly in NICUs for babies until national newborn screening can be introduced in Egypt, and they should be done jointly rather than one by one, to maximize patient survival and decrease death and morbidity.