In Taiwan, Solanum indicum L. has been used in folk medicine for the treatment of inflammation, toothache, ascites, edema, and wound infection. The plant is rich in solanine, an alkaloidal glycoside. We report a 43-year-old man who developed polyuria and polydipsia after taking seven doses of concentrated solution of Solanum indicum L. over two weeks. A water deprivation test and a low serum antidiuretic hormone level helped to confirm a diagnosis of central diabetes insipidus. We suggest that excessive doses of Solanum indicum L. may cause central diabetes insipidus.