Patients with progressive supranuclear palsy often suffer from dysphagia, and percutaneous endoscopic gastrostomy is a treatment option for the advanced stage of this disease. The present percutaneous endoscopic gastrostomy patient had slightly impaired glucose tolerance, but the condition became considerably worse with normal nutrients due to limited activity and an infection after percutaneous endoscopic gastrostomy, resulting in a non-ketotic hyperosmolar coma. After receiving supplementary fluid, intravenous insulin, antibiotics and endotracheal intubation, the patient recovered from the non-ketotic hyperosmolar coma state. Percutaneous endoscopic gastrostomy placement at an advanced stage of a neurodegenerative disorder, such as progressive supranuclear palsy, should have a careful follow-up, especially when glucose tolerance worsens.