Glucose transporter deficiency syndrome (Glut1-DS) is a form of pediatric epilepsy caused by a genetic mutation that disrupts the body's ability to process food from the child's diet into sugar (energy) needed to support brain function. Children with Glut1-DS experience seizures that are not controlled by anticonvulsant medications, as well as delays in cognitive and motor development. Currently, Glut1-DS is treated with the ketogenic diet, a high-fat, low-sugar diet that provides the brain with an alternate source of energy. Despite the significant improvement of seizures upon this diet, seizure control is incomplete in a majority of children, and they continue to experience problems with brain development. Our team of researchers and clinicians with expertise in metabolic diseases, neurology, pediatrics, biochemistry, and genetics believes that there is an opportunity to achieve CURE's goal of "No Seizures/No Side Effects" for children with Glut1-DS by investigating the use of a new treatment option that is designed to compensate for the underlying biochemical deficiency thought to contribute both to the seizures and to the impaired brain development associated with Glut1-DS. The proposed treatment involves incorporating a special type of oil, called triheptanoin, into the ketogenic diet as a way to make up for a specific biochemical deficit affecting kids with Glut1-DS that the standard ketogenic diet fails to address. Our goal is to do a pilot study to test the safety and effectiveness of this promising new treatment option in a small group of children with Glut1-DS.