# Treat hypotonic hyponatremia

Andrew Bland, MD, FACP, FAAP · October 21, 2026

Symptoms first, cause-directed treatment, and control of the correction.

## Protect the brain, then reassess

Severe attributable symptoms such as seizure, coma or major neurologic deterioration call for monitored 3% saline boluses under the local protocol while evaluating the cause. An initial sodium rise of about 4–6 mmol/L often provides useful symptom relief; rapid normalization is not the goal. Moderately severe attributable symptoms also warrant urgent assessment and may justify a monitored bolus.

## Follow the same diagnostic lanes

Hypovolemic: stop offending drugs and losses, replace volume with an appropriate isotonic crystalloid and reassess. Euvolemic/SIAD: treat the trigger; fluid restriction is often initial therapy when stable, with specialist-directed solute therapy when needed. Hypervolemic: address the underlying disease and congestion, with fluid restriction when appropriate. Dilute urine/low solute: reduce excess water and restore nutrition or solute cautiously. These categories can overlap.

## Set a correction plan before treatment

For chronic or uncertain-duration disease at high risk of osmotic demyelination, aim for approximately 4–6 mmol/L over 24 hours and avoid exceeding 8 mmol/L in any 24 hours. Major risk factors include very low sodium, hypokalemia, malnutrition, alcohol use disorder and advanced liver disease. For other patients, the European guideline limits correction to 10 mmol/L in the first 24 hours and 8 mmol/L per 24 hours thereafter. Limits are ceilings, not targets; account for all treatment and spontaneous changes.

## Monitor water output as well as serum sodium

During active correction, follow serial sodium, urine output and clinical status frequently; monitoring intervals must shorten when the trajectory changes. Potassium replacement contributes to the rise in serum sodium. Volume restoration, thiazide withdrawal or solute replacement may suddenly permit a dilute water diuresis. If correction is running ahead of plan, stop the driver and obtain urgent expert help; desmopressin and electrolyte-free water such as D5W may be needed for controlled relowering.

## Sources

- [Society for Endocrinology: emergency hyponatraemia guidance](https://www.endocrinology.org/media/xhrhxhxm/emergency-management-of-severe-and-moderately-severely-symptomatic-hyponatraemia-in-adult-patients-2022.pdf)
- [Treatment Guidelines for Hyponatremia: Stay the Course](https://pubmed.ncbi.nlm.nih.gov/37379081/)
- [European clinical guideline](https://academic.oup.com/ejendo/article/170/3/G1/6668028)

[Open the infographic](https://urinenephrology.org/visual-reference/day1-hyponatremia-treatment)