Abstract
BACKGROUND: The ketogenic diet (KD) therapy is a primary treatment for drug-resistant epilepsy, and beta-hydroxybutyrate (BHB) is the main ketone produced during KD. However, the pattern of increase in BHB levels is not well understood, and the reference range for BHB need to be defined. The aim of this study was to evaluate the BHB levels in the first three months, especially one week, after KD initiation, and to explore the physiological reference range for BHB. METHODS: In our study, a fasting initiation strategy was used for the majority of patients (252/300, 84%) who underwent fasting for 24-48 h, the rest fasted for at least 12 h. The concentration of blood BHB was measured four times a day during the first week, at one month and three months. Seizure frequency was recorded at one week, one month and three months. Responders were defined as those with a seizure reduction 50% or more compared to baseline. BHB levels were compared between responders and non-responders. The BHB levels of responders were used to calculate the reference range. RESULTS: A total of 300 patients were recruited, of whom 172 (57%) had accessible BHB data. BHB levels rapidly rose to 2.0 mmol/L at 19 h, peaked at 4.2 mmol/L at 43 h of therapy, and stabilized by three months. The reference range for BHB was 1.1 to 4.9 mmol/L. CONCLUSIONS: BHB levels increased rapidly following fasting, reaching the peak at day 2, stabilizing from the end of the first week through three months. The lower reference limit for BHB to ensure KD efficacy should be set at 1.1 mmol/L.