If not super low and not super symptomatic, assess volume status (history, vitals, orthostatics, JVP, skin turgor, mucous membranes, peripheral edema, BUN, Cr) and
- if hypovolemic (thiazides, mineralcorticoid deficiency, diarrhea, vomiting) initiate mild IV hydration w/ NS to decrease ADH production OR
- if euvolemic (SIADH, polydipsia)) or hypervolemic (CHF, end stage kidney failure, cirrhosis), initiate free water/fluid restriction
This empiric approach will generally get patients headed in the right direction until evaled by the internists and/or nephrologists. For those that are more ambitious feel free to send off urine 'lytes and osmoles.
Source
Sabatine, Marc MD. Pocket Medicine: The Massachusetts General Hospital Handbook of Internal Medicine. 3rd ed. 2008.
