First – look to see what the person’s sodium is
Second – what is their volume status
The most important thing about hyponatremia is don’t correct more than 8 to 12 mmol/L per day!!!
Also, the paper titled “The Syndrome of Inappropriate Antidiuresis” by Ellison and Berl (N Engl J Med 2007;356:2064-72) is very useful.