Although hyperglycemia is common in neonates, especially preterm infants, a diagnosis of neonatal diabetes mellitus (NDM) is rarely made. NDM can be permanent (45%), transient (45%) or syndromic (10%). Of the 95% of identifiable mutations for NDM, methylation defects in 6q24, KCNJ11, ABCC8, and INS account for the majority. Two cases of transient NDM in extremely preterm, 24 weeks' gestational age (GA) triplets, due to a missense mutation c.685G>A in the KCNJ11 gene are presented. Both patients were successfully transitioned from insulin to Glyburide (Glibenclamide) at 2 months of age. Comprehensive genetic testing with targeted next-generation sequencing and 6q24 methylation analysis helps identify monogenic diabetes early, thereby improving metabolic and glycemic control when patients with potassium channel mutations are started on sulfonylurea (SU) treatment.