32yo man, who is otherwise healthy with no PMH, presents to your clinic with a 2-month history of polyuria, nocturia, and polydipsia. Both of his parents have DMII and told him he needed “to get his sugar checked”. He denies any weight changes or vision disturbances. Vitals in clinic are BP-112/72 mmHg, HR-108, RR-12, O2-100%, and temp-98.9o. Initial screening labs are below.
- What is the most likely diagnosis?
- What additional labs should be ordered?
This patient likely has diabetes insipidus given the normal glucose/HbA1c and hypernatremia with polyuria. Next step in the diagnostic evaluation would be to check a urine osmolarity and plasma copeptin.