Frequent urination in large large volumes but negative for urine culture, urine analysis, and blood test checking for diabetes. ?

Be seen: You could have another type of diabetes, called diabetes insipidus. Your doctor can check you for it. It could also have overactive bladder or another condition.

Diabetes insipidus ?: The following site covers this topic very well; provides symptoms, causes, workup, treatment. See your doc for additional tests to see if this might be your problem.