How fast can serum sodium be safely corrected?

In chronic hyponatraemia, serum sodium should rise by no more than about 8 mEq/L in any 24-hour period, and 6 mEq/L in patients at high risk of osmotic demyelination such as those with alcoholism, malnutrition, hypokalaemia or advanced liver disease. Correcting faster risks osmotic demyelination syndrome.

What is the Adrogue-Madias formula?

The Adrogue-Madias formula predicts the change in serum sodium from one litre of a chosen infusate: delta sodium equals (infusate sodium plus infusate potassium minus serum sodium) divided by (total body water plus one). It lets you estimate the infusion rate needed to raise sodium by a target amount.

What is osmotic demyelination syndrome?

Osmotic demyelination syndrome, formerly called central pontine myelinolysis, is irreversible brain injury caused by overly rapid correction of chronic hyponatraemia. Symptoms include dysarthria, dysphagia, quadriparesis and locked-in syndrome, often appearing days after the correction. Slow, monitored correction prevents it.

Why does potassium appear in the formula?

Replacing a potassium deficit raises serum sodium too, because potassium is osmotically active and shifts water. The Adrogue-Madias formula adds infusate potassium to infusate sodium so that potassium replacement is accounted for, preventing inadvertent overcorrection.

Does the formula account for ongoing urine losses?

No. The Adrogue-Madias formula assumes a closed system and ignores ongoing renal water and electrolyte losses. When a patient begins a brisk water diuresis, sodium can rise far faster than predicted, so frequent re-measurement every 2 to 4 hours during active correction is essential.

Hyponatraemia Correction Rate Calculator

Safe sodium correction for hyponatraemia

The danger in treating chronic hyponatraemia is not the low sodium itself but correcting it too quickly, which can cause irreversible osmotic demyelination syndrome. This calculator does two things: it states the maximum safe 24-hour rise for the patient, and it uses the Adrogué–Madias formula to estimate the infusion rate of a chosen saline that will reach that target without overshooting.

How it works

The safe ceiling is a fixed clinical limit. This tool uses 8 mEq/L per 24 hours as the standard cap and a stricter 6 mEq/L per 24 hours for patients at high demyelination risk.

The infusion side uses Adrogué–Madias to predict how much one litre of infusate will move the sodium:

ΔNa per litre = (infusate_Na + infusate_K − serum_Na) / (TBW + 1)
TBW = weight_kg × factor   (male 0.6, female 0.5, elderly 0.5 / 0.45)

Dividing the daily target by ΔNa per litre gives the litres of infusate to run over 24 hours, and dividing by 24 gives the hourly rate. Hypertonic 3% saline (513 mEq/L) raises sodium most per litre; 0.45% saline raises it least and may even lower a very low sodium.

Notes and example

For a 70 kg man with a sodium of 115 mEq/L and potassium of 4, each litre of 3% saline is predicted to raise sodium by roughly 9 mEq/L — so well under a litre over 24 hours reaches the 8 mEq/L target.

Treat the predicted rate as a starting point, not a guarantee. The formula ignores urinary losses, and overcorrection often happens when volume repletion triggers a water diuresis. Check serum sodium every 2–4 hours during active correction, and if it is rising too fast, re-lower with desmopressin (DDAVP) and free water.