Abstract Disclosure: M. Bertossi: None. C. Lowe: None. Q.L. Van Meter: Consulting Fee; Self; Eton Pharmaceuticals. Speaker; Self; Eton Pharmaceuticals. Introduction: Congenital adrenal hyperplasia (CAH) is the most common cause of pediatric adrenal insufficiency. Children diagnosed with CAH need exogenous glucocorticoid therapy throughout their lifetime. Because low dose hydrocortisone (HC) tablets are not available, patients and their caregivers must either split/crush hydrocortisone tablets or rely on HC that has been compounded from adult medications. In late 2020, a pediatric specific HC formulation, an oral granule, became available with doses as low as 0.5 mg. There are minimal data concerning the long-term use of this novel HC formulation. Subject and Method: This case study is a girl (DOB 11/2016) with CAH who has been administered the HC oral granule formulation for over 3 years. Results: The subject is a 7-year-old female who was diagnosed at birth with CAH. At an outside institution, she administered 6.25 mg HC, divided into three doses of 2.5 mg in the morning, 1.25 mg in the afternoon, and 2.5 mg in the evening (2.5/1.25/2.5; 9 mg/m2). She was also administered 0.15 mg fludrocortisone qd. Her dose was increased to a total dose of 7.5 mg, administered 2.5 mg three times/day (10 mg/m2) because of a high 17-OHP concentration, 1048 mg/dL. Other hormone levels were unremarkable. Her 17-OHP levels increased to 2662 mg/dL after 3 months of the increased dose. Because of the development of Cushing’s symptoms, she was switched to the 7.0 mg HC granules (2.5/2.0/2.5; 9.5 mg/m2 total dose). After the switch to the HC granules, her 17-OHP levels was 293 ng/dL. Because of rising 17-OHP levels, her dose needed to be increased twice over the past 2 yrs. Her current dose is 12 mg HC granules (4/4/4; 11 mg/m2 total dose), and her three most recent 17-OHP levels were 73, 101, and 89 ng/dL, respectively. She is also taking 0.2 mg fludrocortisone po, q am. Throughout HC granule therapy, she had no incidence of adrenal crisis. Her most recent calculated bone age was 8 yr 10 mo, with her chronological age was 6 yr, 8 mo with no evidence of virilization. Growth curves suggest that she is neither under- nor over-dosed on her HC therapy. Conclusion: This case may be the longest, continuous administration of the novel HC granules in US for a child with CAH. The results show the potential to better titrate HC dosing, especially with the narrow therapeutic window of HC in children with CAH. Her daily dose was adjusted by titrating in small increments to result in good outcomes, such as better hormonal control, the lack of virilization and continuous growth. Further evaluations of the long-term use of HC granules are needed to occur to establish the long-term risks and benefits of this novel HC granule. Presentation: 6/3/2024