Abstract Disclosure: J. Yoo: None. S. Kim: None. H. Chae: None. Introduction: The Modified Atkins Diet (MAD), as a type of Ketogenic diet (KD) therapy, is utilized as a treatment for intractable epilepsy. Compared to the classic KD, it has a lower ratio of fat to carbohydrate plus protein, resulting in higher compliance among patients. Dyslipidemia is known as a major complication of KD, but when it comes to MAD, there is a scarcity of long-term studies investigating lipid level alterations in children.In this study, our objective is to examine the impact of the MAD on serum lipid levels in children and adolescents with intractable epilepsy. Method: A total of 106 patients with intractable epilepsy aged under 19 who initiated MAD from January 2016 to December 2021 and maintained MAD for a minimum of 12 months were enrolled. Laboratory test for lipid level were conducted at baseline, 1 month, 3 months, 6 months, and subsequently at 6-month intervals after initiation of MAD. The prevalence rate of dyslipidemia and lipid levles by period after MAD was analyzed. Dyslipidemia is defined as having any one of the following criteria: total cholesterol ≥200 mg/dL, LDL (Low-density lipoprotein) ≥130 mg/dL, HDL (High-density lipoprotein) <40 mg/dL, and triglyceride ≥100 mg/dL for children aged 0-9 and ≥130 mg/dL for adolescents aged 10-18.3. Result: The prevalence rate of total dyslipidemia observed at baseline, 1 month, 3 months, 6 months, 12 months, 18 months, 24 months, 30 months, and 36 months, were 31.1%, 67.6%, 69.5%, 68.2%, 59.5%, 60.5%, 53.7%, 47.1%, and 31.3%, respectively. When the average value and prevalence rate for each type of dyslipidemia were analyzed, total cholesterol and LDL levels showed an increase from the 1-month period compared to the baseline, peaked at the 3-month period, and gradually decreased from the 6th month with statistical significance. In the case of triglycerides, the prevalence rate of hypertriglyceridemia was highest at 3 months, but the average value was highest at 1 month with statistical significance. However, in HDL, both the average value and the prevalence rate of hypo-HDL cholesterolemia did not exhibit a significant difference over the entire period. Conclusion: MAD increases the incidence of dyslipidemia until three months after initiation, but in most cases, it tends to decrease even without treatment after six months. Presentation: 6/1/2024