The obvious suspicion
The patient drank water constantly and woke several times at night to urinate. Diabetes seemed likely.
The unexpected result
Repeated glucose measurements were not high enough to explain the symptoms. There was also constipation, fatigue and mild confusion.
The twist
Blood tests showed significant hypercalcaemia. The polyuria and thirst were metabolic, but not due to diabetes.
Take-home message
Polyuria and polydipsia have a differential diagnosis. When glucose does not explain the picture, review calcium, kidney function, medicines and water-balance disorders.
Diagnostic principle: do not let the first plausible label stop the search when an important detail does not fit.
Educational note: This is a teaching composite, not a substitute for patient-specific diagnosis or treatment. Real patients require direct clinical assessment and appropriate investigations.