# Hypokalemia: Loss, Shift, Magnesium, and Replacement

Identify loss versus shift, use urine and acid–base findings to localize the mechanism, and replace potassium with magnesium and kidney function in view.

![Infographic: Hypokalemia: Loss, Shift, Magnesium, and Replacement](https://urinenephrology.org/visual-reference/images/student-hypokalemia.png?v=20261003c)

## Identify urgency

K <2.5 mmol/L, arrhythmia/ECG change, paralysis, severe weakness, or respiratory involvement warrants urgent monitored treatment. Cardiac disease, digoxin, rapid decline, and low magnesium increase risk. A stable mild reduction and a symptomatic rapid fall do not use the same pathway.

## Separate loss from redistribution

Diarrhea/laxatives, vomiting, and diuretics cause loss; insulin, beta agonists, and alkalosis can shift K into cells. Ask about poor intake and recent treatment. Reversal of a shift can produce rebound hyperkalemia if replacement is excessive.

## Use urine potassium with context

During hypokalemia, spot urine K:creatinine >13 mEq/g suggests inappropriate renal loss. Check units, muscle mass, current replacement, diuretics, and collection timing. A low value supports appropriate renal conservation but does not independently identify the exact extrarenal cause.

## Add acid–base and BP

Acidosis plus low urine K suggests GI bicarbonate loss; renal loss prompts tubular/drug evaluation. Alkalosis with low urine chloride suggests gastric or remote diuretic loss. Hypertension with renal K wasting raises concern for mineralocorticoid-related disease.

## Choose a safe route and salt

Oral KCl is preferred for many stable patients who can absorb it. IV replacement is reserved for severe/symptomatic disease, relevant ECG changes, or inability to use the gut, with controlled infusion and monitoring. KCl also corrects chloride depletion in alkalosis.

## Correct the reason it stays low

Check and replace magnesium while treating potassium—do not delay urgent K replacement waiting for magnesium normalization. Recheck according to severity, route, ongoing losses, and kidney function. Continued low K after replacement should trigger a search for ongoing loss, not an assumed fixed body deficit.

## Supporting evidence

- [Supporting guideline or source](https://pmc.ncbi.nlm.nih.gov/articles/PMC5881435/)

## Source lessons

- [chapter 12 electrolytes](https://urinenephrology.org/nephrology-textbook/chapters/chapter-12-electrolytes.html)
- [hypokalemia student handout](https://urinenephrology.org/student-resources/electrolyte-acid-base/hypokalemia-student-handout.html)

Read alongside the full lessons; the findings and decisions shown here require the stated clinical context.