Increased levels of intracellular calcium are thought to diminish maximal cellular response to insulin and induce insulin resistance. Also, both hypertension and diabetes are thought to be conditions of altered intracellular ionic state. The aim of the present study is to investigate the possible effect of oral calcium supplementation on intracellular ions, insulin sensitivity, 24-h blood pressure and sodium/hydrogen exchanger activity in patients with type 2 diabetes and essential hypertension.