Estimate an adult potassium deficit with 0.4 × weight × (4.5 − serum K) in mEq and grams of KCl, or find infusion time or rate for a set dose.

B. Braun product-label model for adult moderate deficiency or maintenance; fixed target 4.5 mmol/L. Not a measured total-body deficit or a prescription.

Optional settings

Medical safety notice: This tool provides an educational product-label approximation, not a measured total-body deficit or a prescription. The dosing/infusion planner outputs are intended for licensed clinicians and must be verified against your institutional protocol and current potassium chloride safety guidance (e.g., FDA labeling). Potassium replacement can be dangerous and typically requires appropriate dilution, infusion pump use (never IV push/bolus), ECG/lab monitoring, and consideration of kidney function and interacting medications (e.g., ACE inhibitors/ARBs, potassium-sparing diuretics). If you have concerning symptoms (palpitations, severe weakness, paralysis), seek urgent medical care.

Potassium Replacement Formula

The adult moderate-deficiency/maintenance approximation below comes from B. Braun’s potassium chloride 0.15% and glucose 5% product information, section 4.2. Its fixed target is 4.5 mmol/L. This product-specific model is not a measured total-body deficit or a prescription.

KR = (4.5 - C) × W × 0.4

Variables:

  • KR is the model approximation in mmol (numerically equal to mEq for potassium)
  • The model target is fixed at 4.5 mmol/L
  • C is the measured serum potassium in mmol/L
  • W is the patient’s weight in kilograms

Subtract measured serum potassium from 4.5 mmol/L, then multiply by adult weight in kilograms and 0.4. The approximation applies only below that target. Clinical cause, renal function, ECG and repeat laboratory monitoring govern treatment; the calculator does not predict the resulting serum concentration.

What is a Potassium Replacement?

Potassium replacement is a medical treatment used to correct or prevent low levels of potassium in the body, a condition known as hypokalemia. This can be caused by certain medications, illnesses, or inadequate dietary intake. Potassium replacement can be administered orally or intravenously, depending on the severity of the deficiency. It is crucial for maintaining heart, nerve, and muscle cell functions.

How to Calculate Potassium Replacement?

The following steps illustrate the adult product-label approximation (KR), not a treatment plan. The separate infusion modes use dose ÷ rate for time or dose ÷ time for rate.

  1. First, use the model’s fixed target of 4.5 mmol/L.
  2. Next, determine the current potassium level (C).
  3. Next, determine the patient’s weight in kilograms (W).
  4. Next, gather the formula from above = KR = (4.5 – C) * W * 0.4 (the coefficient and target belong to the named product-label approximation).
  5. Finally, calculate the Potassium Replacement (KR).
  6. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

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

Fixed model target = 4.5 mmol/L

Current potassium level (C) = 3.8 mmol/L

Patient’s weight in kilograms (W) = 70. The model gives (4.5 − 3.8) × 70 × 0.4 = 19.6 mmol; this is an arithmetic illustration, not a recommended dose.