Nursing care
Potassium Imbalances nursing care: what to assess and what to do first
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Potassium imbalances are managed by treating the ECG, not the number. Both hyperkalaemia and hypokalaemia cause life-threatening arrhythmias, and the tracing changes before symptoms do. Get a 12-lead or continuous strip on any patient with an abnormal potassium, correct the level according to protocol, and reassess the rhythm rather than waiting for the patient to feel unwell.
Recognising it at the bedside
Hyperkalaemia presents with muscle weakness that starts in the legs and moves upward, paraesthesia, and a sense of heaviness the patient may describe as legs that will not respond properly. Hypokalaemia looks similar from the outside: weakness, fatigue, leg cramps, and in more severe cases flaccid paralysis. Both conditions can produce constipation or ileus, and both can leave a patient looking stable in the chair while the cardiac conduction system is already compromised.
The distinguishing feature is rarely the symptom itself, it is the trend. A potassium of 6.2 mmol/L in a patient on a potassium-sparing diuretic with declining urine output tells a different story to a potassium of 6.2 mmol/L from a haemolysed sample. Correlate the number against the medication list, renal function, and how the specimen was drawn before treating a result that does not match the patient in front of you.
Why the classic presentation misleads
Textbooks teach hyperkalaemia as tall peaked T waves and hypokalaemia as flattened T waves with U waves, and both are correct, but neither reliably shows up before the arrhythmia does. A patient can move from a normal sinus rhythm to ventricular fibrillation with a potassium of 7.5 mmol/L without ever reporting palpitations. The symptom burden in mild to moderate imbalance is often subtle fatigue that gets attributed to the primary admission diagnosis rather than to potassium.
This is the core teaching point for both directions: the ECG is the monitor, not the symptom. A patient who feels fine can still be minutes from a lethal rhythm, and a patient who feels dreadful with cramping may have a potassium that is only mildly deranged. Treat every abnormal potassium as an indication to look at the rhythm strip, not as a cue to wait and see how the patient feels.
Priority nursing actions
Place the patient on continuous cardiac monitoring or obtain a 12-lead ECG as the first action for any critical potassium value, before you chase a repeat sample or call the lab to query the result. Hold any potassium-altering medication, including potassium chloride infusions, potassium-sparing diuretics, ACE inhibitors, and ARBs, until the physician has reviewed the value.
For hyperkalaemia, anticipate calcium gluconate to stabilise the cardiac membrane, insulin with dextrose to shift potassium intracellularly, and possibly sodium bicarbonate or a beta-agonist nebuliser, followed by a definitive removal strategy such as a potassium binder or dialysis. For hypokalaemia, anticipate oral or IV potassium replacement, never IV push, with the infusion rate strictly limited and the line checked for correct dilution. In either direction, recheck the ECG after intervention rather than assuming the lab value alone confirms resolution.
Labs and diagnostics to expect
A basic metabolic panel or renal function panel accompanies every potassium result, because the cause and the correction strategy both depend on renal function. Expect magnesium to be drawn alongside potassium, since hypomagnesaemia commonly drives refractory hypokalaemia and magnesium must be corrected first or the potassium will not hold.
Arterial blood gas may be ordered because acid-base status shifts potassium between the intracellular and extracellular space independent of total body stores, so a patient can appear hyperkalaemic on a gas from acidosis alone. Continuous ECG monitoring functions as an ongoing diagnostic tool through the correction period, not just a one-off test at presentation.
Complications and their early signs
The shared complication across both imbalances is a lethal dysrhythmia, and the early sign is a widening QRS or a new arrhythmia on the strip, not a change in how the patient reports feeling. In hyperkalaemia, watch for the progression from peaked T waves to a widened QRS to a sine-wave pattern, which precedes cardiac arrest.
In hypokalaemia, watch for the progression from flattened T waves to U waves to ventricular ectopy, particularly in a patient on digoxin, where hypokalaemia potentiates digoxin toxicity. Rhabdomyolysis is a recognised complication of severe hypokalaemia, so escalating muscle pain with dark urine warrants a creatine kinase level, not reassurance.
Teaching that changes outcomes
Patients on loop or thiazide diuretics need explicit teaching on potassium-rich foods, such as bananas, oranges, potatoes, and leafy greens, and on recognising the muscle weakness that should prompt a call rather than a wait-and-see approach. Patients on potassium-sparing diuretics, ACE inhibitors, or ARBs need the opposite message, that salt substitutes are frequently potassium chloride and should be avoided.
Anyone discharged on an oral potassium supplement should understand that missed follow-up bloods are the most common reason for a preventable readmission, since the therapeutic window is narrow in both directions. Teaching that ties the medication to the monitoring plan, rather than treating them as separate instructions, is what actually changes whether the follow-up happens.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our reduction of risk potential practice questions are the closest set to what this page covers.
One question from the reduction of risk potential set
Four hours after a cardiac catheterization via the right femoral artery, the nurse notes the client's right dorsalis pedis pulse is now faint and the foot is cool and pale. What is the nurse's priority action?
Rationale
A pulse that was present and is now faint, with a cool, pale extremity distal to the puncture site, is arterial occlusion until proven otherwise — a limb-threatening complication that needs the provider now. Documenting and rechecking wastes the window, warming treats the symptom and masks the change, and asking the client to move the ankle neither restores flow nor gives you new information.
Answer: C
Common questions
What ECG changes come first in hyperkalaemia?
Peaked, narrow T waves are typically the earliest change, followed by PR prolongation, a widening QRS, and eventually a sine-wave pattern as the level climbs further. The progression can move quickly, so a single abnormal strip in a patient with a known high potassium should trigger immediate escalation rather than a repeat in an hour.
Why is IV potassium never given as a push?
A rapid IV push delivers a high local concentration directly to the heart before it can distribute, which can trigger cardiac arrest even at a total dose that would be safe infused slowly. IV potassium is always diluted and rate-limited according to unit protocol, with the infusion on a pump and the line checked before it starts.
Does hypokalaemia always need magnesium checked too?
Yes, low magnesium is a common and under-recognised cause of potassium that will not correct despite adequate replacement. If magnesium is low, correct it first or alongside the potassium, since the kidneys will continue wasting potassium while magnesium remains depleted.
How urgent is a potassium of 6.8 mmol/L with a normal ECG?
Still urgent. A normal-looking strip at that level does not mean the risk has passed, it means the change has not shown up yet, and it can appear within minutes. Continuous monitoring and treatment should start immediately rather than waiting for ECG confirmation.
What is the NCLEX-style priority action for a critical potassium result?
Assess the cardiac rhythm before doing anything else, since airway and breathing are not the immediate threat here, circulation via the conduction system is. On a question stem, the answer that involves the monitor or ECG will usually outrank an answer about calling the physician or rechecking the lab.
More on reduction of risk potential