Gitelman's syndrome (GS) is characterized by hypokalemia, hypomagnesaemia, hypocalciuria, metabolic alkalosis, and neurological symptoms. The association of GS with type 1 diabetes is rare, described only in a few case reports. We report a patient with an unusual combination of GS and type 1 diabetes mellitus with erythrocytosis. A 26-year-old male with GS and type 1 diabetes, who was on intensive insulin therapy with poor compliance, presented with the complaint of headache. On physical examination, his blood pressure was 120/70 mmHg and there was no neurological deficit or proximal muscle weakness. He had no previous medical history of obstructive sleep apnea, heart or lung disease. He had negative smoking history. His laboratory tests revealed erythrocytosis with a hemoglobin level of 18.9 g/dL (13.6-17.2 g/dL) and a hematocrit level of 54.8% (39.5-50.3%). Cranial magnetic resonance imaging was normal. He had no evidence of hypovolemia. Hematological workout excluded polycythemia vera and chronic myeloid neoplasm. A bone marrow aspiration revealed a hypercellular marrow with increased erythroid precursors, megakaryocytes and granulocytes. The reticulin stain grade was zero. There was no iron accumulation with iron stain. There was no radiologic evidence of any kind of erythropoietin-producing tumors. His echocardiography was normal. Serum insulin-like growth factor-1 levels and endogenous androgens were within normal limits. After 2 therapeutic phlebotomies, his symptoms improved and his hemoglobin was 16.1 mg/dL. Our patient, besides having GS and type 1 diabetes, was complicated with idiopathic erythrocytosis, all having deleterious effects on hemodynamic status of the patient.