The first mutations identified inSLC2A1, encoding the glucose transporter type 1 (GLUT1) protein of the blood–brain barrier, were associated with severe epileptic encephalopathy. Recently, dominantSLC2A1mutations were found in rare autosomal dominant families with various forms of epilepsy including early onset absence epilepsy (EOAE), myoclonic astatic epilepsy (MAE), and genetic generalized epilepsy (GGE). Our study aimed to investigate the possible role ofSLC2A1in various forms of epilepsy including MAE and absence epilepsy with early onset. We also aimed to estimate the frequency of GLUT1 deficiency syndrome in the Danish population. One hundred twenty patients with MAE, 50 patients with absence epilepsy, and 37 patients with unselected epilepsies, intellectual disability (ID), and/or various movement disorders were screened for mutations inSLC2A1. Mutations inSLC2A1were detected in 5 (10%) of 50 patients with absence epilepsy, and in one (2.7%) of 37 patient with unselected epilepsies, ID, and/or various movement disorders. None of the 120 MAE patients harboredSLC2A1mutations. We estimated the frequency ofSLC2A1mutations in the Danish population to be approximately 1:83,000. Our study confirmed the role ofSLC2A1mutations in absence epilepsy with early onset. However, our study failed to support the notion thatSLC2A1aberrations are a cause of MAE without associated features such as movement disorders.