This is the second tutorial in the series on Hyponatremia. I initially discuss why it is important to evaluate volume status in the setting of a low plasma sodium – patients may be isovolemic, hypovolemic or hypovolemic. The overall treatment is different in each case. Regardless, if a patient presents with symptomatic hyponatremia, then the treatment is 3% hypertonic saline solution – targeted at raising the plasma sodium or osmolality level or both and relieving symptoms. During the remainder of the tutorial I explore several clinical scenarios where patients present with acute symptomatic hyponatremia and work the problem of each seeking the definitive diagnosis.