Potassium Deficit

How to use it

1. 1

   Rough estimate only. K deficit (mmol) ≈ (4.2 − measured K) × weight × 0.4.

2. 2

   Rate limit: 10–20 mmol/h IV. Maximum safe peripheral IV rate = 10 mmol/h. Via central line max 20 mmol/h (continuous ECG).

3. 3

   Never give IV K as bolus. K boluses cause lethal arrhythmias. Always diluted infusion.

When to use it

DKA potassium replacement

Start KCl when K < 5.5 and urine output confirmed. Replace before insulin in K < 3.5.

Diuretic-induced hypokalaemia

Thiazides: mild persistent hypokalaemia; add ACEi/ARB or K-sparing diuretic.

Refractory hypokalaemia

Check and replace magnesium first — hypomagnesaemia prevents K repletion.