Diagnosis of diabetes insipidus is usually based on the medical history, physical exam, lab tests, and imaging tests. Urine tests, including a water deprivation test, will often be used when DI is suspected. With this test, water is withheld until the person loses a certain percentage of his or her body weight. Blood and urine tests are checked routinely to evaluate the reaction of the body to the lack of water. Ultrasound,MRI, and CT scan are commonly used imaging tests to check for brain injury, tumors, or kidney problems.