Calculate a potassium deficit estimate with the adult formula 0.4 × weight × (4.5 − serum K), or solve the equation with your own target and coefficient.

Named adult moderate-deficiency/maintenance model: 0.4 × kg × (4.5 − measured potassium). Fixed assumptions; not a prescription.

Optional settings

Medical safety note: This calculator provides a simplified educational estimate and is not a prescription or dosing recommendation. Potassium replacement can be dangerous (risk of hyperkalemia, arrhythmias, and death) and must be ordered and monitored by a licensed clinician with repeat labs and ECG monitoring when indicated—especially if there is kidney disease/dialysis or use of medications that raise potassium (e.g., ACE inhibitors, ARBs, potassium-sparing diuretics). For treatment decisions, follow local hospital protocols and professional guidelines.

Potassium Repletion Formula

The initial mode uses the adult moderate-deficiency/maintenance approximation in B. Braun’s potassium chloride 0.15% and glucose 5% product information, section 4.2: K = 0.4 × W × (4.5 − C). The custom equation below preserves arbitrary assumptions and inverse arithmetic; those extensions are not the named product-label model.

K = (D - C) × W × f

Variables:

  • K (called A in the widget) is the equation amount in mmol, numerically equal to mEq for potassium
  • D is a custom scenario target concentration (mmol/L), fixed at 4.5 in the named model
  • C is the current potassium level (mmol/L)
  • W is the patient's weight (kg)
  • f is an assumed equation coefficient in L/kg. The custom mathematical default is 0.4; it does not measure patient-specific distribution volume.

For the custom amount equation, subtract C from D, then multiply by weight W and coefficient f. Equal concentrations give zero amount; a negative difference is outside this repletion scenario. This amount is not a measured total-body deficit.

What is a Potassium Repletion?

Potassium repletion is a medical treatment process that involves the restoration of normal potassium levels in the body. Potassium is a vital mineral and electrolyte that plays a crucial role in various bodily functions such as nerve and muscle cell functioning, heart function, and maintaining fluid balance. When the body's potassium levels are low, a condition known as hypokalemia, it can lead to serious health issues. Therefore, potassium repletion, often through oral or intravenous supplementation, is necessary to correct this imbalance.

How to Calculate Potassium Repletion?

Select Custom equation: amount for the steps below, using K = (D - C) * W * f. Other custom modes rearrange this equation to solve target concentration, current concentration or weight; none predicts an unmeasured clinical quantity.

  1. First, supply the custom scenario target D in mmol/L; it is not an automatically recommended clinical target.
  2. Next, determine the current potassium level (C) in mmol/L.
  3. Next, determine the patient's weight (W) in kg.
  4. Set the assumed coefficient f in Equation assumptions and display, or retain the disclosed mathematical default of 0.4. Collapsing the section does not discard it.
  5. Multiply the difference between the desired and current potassium levels (D - C) by the patient's weight (W).
  6. Multiply the result by the selected factor (f) to obtain K.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Custom scenario target (D) = 4 mmol/L

Current potassium level (C) = 3 mmol/L

Patient's weight (W) = 70 kg. With assumed f = 0.4, the custom equation gives (4 − 3) × 70 × 0.4 = 28 mmol. The separate named model instead fixes D = 4.5 and gives 42 mmol. Neither example is a recommended dose.