Measure plasma electrolyte concentrations every 4 to 6 hours for the first 24 hours, and then adjust the frequency based on the treatment response and clinical judgment NICE CG174.
In cases of acute hyponatraemia with moderate or severe symptoms, monitor plasma sodium levels hourly during treatment, especially when administering hypertonic saline, and decrease monitoring frequency as symptoms resolve NICE CKS.
For patients developing hyponatraemia during intravenous fluid therapy, review fluid status and consider more frequent monitoring of serum sodium, urine sodium, and osmolality, particularly if symptoms are present or worsening NICE NG29.
In children and young people, plasma sodium should be checked at least hourly during acute management, especially when administering boluses of hypertonic saline, and then less frequently as symptoms improve NICE NG29.
In adults, monitor serum sodium and chloride daily if receiving IV fluids containing chloride >120 mmol/l, and reassess IV fluid prescriptions if abnormalities develop NICE CG174.