Note: urinary sodium levels may be increased by diuretic therapy (>20 meq/l) and are then therefore of less value.

Note: Other causes of hyponatremia remain possible:

• SIADH (syndrome of inappropriate ADH secretion) due to malignancies, lung diseases, neurological diseases or drugs (SSRI, TCA, antipsychotics, …).
• Adrenal insufficiency (hypoaldosteronism).
• Hypothyroidism.
• Cerebral salt wasting (in subarachnoid hemorrhage).
• Polydipsia.
• …

Note: Too rapid correction of hyponatremia should be avoided, as this can cause very serious neurological complications (central pontine myelinolysis).

• Correct if no symptoms < 5 mmol/l per day.
• Correct if < 125 mmol/l and symptoms up to a maximum of 10 mmol/ per day.