Sudden onset of horizontal diplopia in an elderly patient can be due to giant cell arteritis. Although the patient reported was a vasculopath, a concurrent headache, mild reduction in visual acuity, scalp tenderness and raised inflammatory markers lead to a diagnosis of giant cell arteritis (GCA) and commencement of steroids. After an inconclusive temporal artery biopsy and resolution of visual acuity, the steroids were stopped, but within this time her hypertensive and diabetic treatment had been markedly disturbed. The rationale for treatment is discussed