The following laboratory tests may be helpful in the diagnosis of SIADH:
Serum sodium, potassium, chloride, and bicarbonate
Plasma osmolality
Serum
creatinine
Blood urea nitrogen
Blood glucose
Urine osmolality
Serum
uric acid
Serum cortisol
Thyroid-stimulating hormone
ALSO
The basic diagnostic criteria is as under:
Laboratory findings in diagnosis of SIADH include:
Euvolemic hyponatremia 40 mEq/L with normal dietary salt intake.