Here we describe a patient with a rare movement disorder, hemichorea-hemiballismus, which is described as a complication of non-ketotic hyperglycaemia. This complication may be seen in individuals with poorly controlled long-standing diabetes mellitus. Proper diagnosis is established with CT and MRI of the brain, which typically show classic findings in the basal ganglia. Treatment focuses on improvement of glycaemic control and usually results in rapid resolution of the movement disorder. Nevertheless, recurrent episodes of hemichorea-hemiballismus, and even more ominous complications such as ischaemic stroke may occur.