Hypoglycemic encephalopathy is a potentially life-threatening event that can result in permanent brain injury. This syndrome is not well described in the literature. We report a case of hypoglycemic encephalopathy in a 33-year-old male with type 1 diabetes following a presumed accidental catastrophic insulin overdose. He was found unresponsive following a prolonged hypoglycemic period estimated to be 17 hours. Upon arrival his blood sugar level (BGL) was too low to be recorded and his Glasgow Coma Scale (GCS) was 5. He was normothermic with a pH of 7.32 and had a lactate of 3.3 mmol/L. Despite rapid normalisation of his BGLs with 10% dextrose, he had minimal improvement in his GCS. He was intubated and transferred to the intensive care unit (ICU). A CT of his brain was suggestive of diffuse cerebral oedema. He progressed to a bi-frontal craniotomy to relieve his presumed raised intracranial pressures. Magnetic resonance imaging (MRI) of his brain performed day 6 post admission showed elevated T2 and flair signals throughout his cortex and elevated signal on the diffusion weighted imaging (DWI) was consistent with diffuse cytotoxic oedema. The basal ganglia was hyperintense on FLAIR and T2 images, however the thalami were spared. Reduced apparent diffusion coefficient (ADC) signal throughout the subcortical white matter was noted. He had minimal neurological improvements clinically and an electroencephalogram (EEG) showed very low voltage output in keeping with minimal cortical activity. In view of above findings, he was felt to have no prospect of recovery and was palliated. In summary, we report a case of severe hypoglycemic encephalopathy resulting in fatal metabolic brain injury that was difficult to prognosticate. The syndrome is associated with characteristic MRI findings as described in our case. We attribute prolonged hypoglycemia, normothermia and DWI findings as predictors of poor outcome in this case.