Question 1

How much KCl raises serum potassium by 1 mEq/L?

Accepted Answer

Approximately 100 mEq of supplemental KCl raises serum K by about 1 mEq/L in a patient with normal kidney function. The rule of thumb is "10 mEq → 0.1 mEq/L rise," though it varies considerably with renal function, acid-base status, and ongoing losses.

Question 2

What is the maximum IV potassium infusion rate?

Accepted Answer

Through a peripheral line, 10 mEq/hr is the standard maximum (phlebitis risk above this). Through a central line with telemetry monitoring, 20 mEq/hr is the upper limit. Higher rates are sometimes used in critical illness with continuous ECG monitoring, but never IV push — bolus or rapid push of potassium is a guaranteed lethal arrhythmia.

Question 3

Why do I need to check magnesium before replacing potassium?

Accepted Answer

Magnesium is required for the renal Na/K-ATPase that retains potassium. With low magnesium, the kidney continues wasting K despite supplementation, and serum K levels won't budge. Refractory hypokalemia is almost always a hypomagnesemia problem. Replace Mg if serum is below ~2.0 mg/dL — concurrently with K replacement or first.

Question 4

When do I use IV vs PO potassium?

Accepted Answer

PO is the route of choice for mild to moderate hypokalemia (K 3.0–3.4) in patients who can take oral medication. IV is required for severe hypokalemia (<2.5), symptomatic patients, ECG changes, or NPO status. A combined PO + IV approach is often used in moderate-to-severe cases to repete faster while remaining within IV rate caps.

Question 5

What's the goal potassium in DKA?

Accepted Answer

Aim for K 4–5 mEq/L throughout DKA management. Insulin drives K intracellularly, so what looks like a normal K on admission can drop precipitously once insulin starts. Hold insulin if K < 3.3 and replace K first; add K to fluids when K < 5.5.

Question 6

How does CKD change potassium replacement?

Accepted Answer

Reduced K excretion in CKD means each milliequivalent supplemented produces a larger and longer-lasting rise in serum K. Replace cautiously, often in 20 mEq increments with a recheck after each, and avoid empiric "deficit replacement" — the math overshoots in CKD.

Potassium Replacement Estimator

References

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