Nursing care
Spironolactone: what to check before you give it
Written and reviewed by Dana Whitfield, RN, MSN · 4 min read · Updated September 2026
Short answer
Spironolactone is a potassium-sparing diuretic, so the priority nursing consideration is hyperkalaemia. Hold potassium supplements and salt substitutes, monitor serum potassium closely, and watch for the risk doubling when an ACE inhibitor is prescribed alongside it. Men should be warned about gynaecomastia before they notice it themselves.
Why this drug and not another
Spironolactone blocks aldosterone at the distal nephron, so it holds onto potassium while it pushes out sodium and water. That single mechanism is why it gets chosen over a loop or thiazide diuretic for heart failure with reduced ejection fraction, resistant hypertension, and ascites from cirrhosis: the patient keeps potassium instead of wasting it.
It's also an aldosterone antagonist first and a diuretic second in modern practice. In heart failure, the mortality benefit comes from blocking aldosterone's effect on cardiac remodelling, not from the diuresis itself, which is why low doses are used even in patients who don't look fluid-overloaded. Know that distinction; it explains why the dose looks too small to be a 'real' diuretic on the chart.
Administration and timing
Give with food to reduce GI upset and improve absorption. If it's ordered once daily, morning dosing is preferred to avoid nocturia, though twice-daily regimens are common in ascites management and should be split as ordered rather than consolidated.
Check the most recent potassium and renal function before you give it, not just at admission. In heart failure and cirrhosis patients especially, renal function can shift day to day, and a potassium that was 4.2 on Monday can be 5.6 by Thursday if an ACE inhibitor or NSAID has been added.
Monitoring parameters
Serum potassium is the parameter that matters most. Baseline before starting, then rechecked within the first week and periodically thereafter, more frequently if renal function is impaired or the patient is also on an ACE inhibitor, ARB, or another potassium-sparing agent.
Track renal function alongside potassium, since reduced GFR is what turns a safe dose into a dangerous one. Blood pressure and daily weight round out the picture in heart failure and ascites patients, where fluid status changes matter as much as the electrolyte.
Adverse effects to report
Hyperkalaemia is the effect that can kill quietly. Peaked T waves, muscle weakness, paraesthesia, or a potassium above the lab's upper limit all warrant an immediate call, not a note for the next round.
Gynaecomastia is the effect that gets missed because nobody asks. It develops in a meaningful minority of men on spironolactone, is dose-related, and is often the reason patients stop taking the drug without telling anyone why. Ask directly rather than waiting for the patient to volunteer it.
Contraindications and cautions
Hyperkalaemia at baseline, significant renal impairment, and Addison's disease are contraindications, since the drug's whole action works against the body's ability to clear potassium. Use caution in any patient with borderline renal function, where a small drop in perfusion can tip potassium clearance over the edge.
The combination to watch hardest is spironolactone with an ACE inhibitor or ARB. Both drugs raise potassium through different mechanisms, and giving them together roughly doubles the risk of clinically significant hyperkalaemia compared with either alone. That combination is still used deliberately in heart failure, so the answer isn't to avoid it, it's to monitor harder when it's ordered.
Teaching points the exam tests
No potassium supplements, no salt substitutes. That single teaching point is tested repeatedly because it's the most common patient-driven cause of hyperkalaemia on this drug, since many salt substitutes are potassium chloride rather than sodium chloride and patients don't read the label as a drug interaction.
Tell men specifically to expect and report breast tenderness or enlargement, and tell every patient to report muscle weakness or an irregular heartbeat. Reinforce that this isn't a drug to stop abruptly without medical advice, since it's often part of a heart failure or ascites regimen where sudden withdrawal has its own consequences.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our pharmacology practice questions are the closest set to what this page covers.
One question from the pharmacology set
A client with heart failure is started on furosemide 40 mg PO daily. Which findings should the nurse report to the provider before administering the next dose? Select all that apply.
Rationale
Furosemide is a loop diuretic, so the two things you are watching are potassium and kidney function. A potassium of 2.9 mEq/L is below the 3.5–5.0 reference range and puts the client at risk for dysrhythmia — hold and report. Muscle cramps with palpitations are the clinical face of that same hypokalemia, so they are reported together, not separately. A creatinine that doubles signals the diuresis has outrun renal perfusion. A blood pressure of 132/78 and a 1 kg loss are the expected response to the drug working, not reasons to hold it.
Answer: A, D, E
Common questions
Can a patient on spironolactone eat bananas or other high-potassium foods?
Moderate intake of potassium-rich foods like bananas is generally fine and isn't the same risk as a potassium supplement or salt substitute. The bigger concern is concentrated potassium sources, so counsel on avoiding added potassium chloride products rather than restricting normal fruit and vegetable intake, unless renal function or a lab result says otherwise.
Why does spironolactone cause gynaecomastia?
Spironolactone has anti-androgen activity in addition to blocking aldosterone, and that anti-androgen effect is what produces breast tissue development in men. It's dose-related, so a lower dose or a switch to eplerenone, which has less anti-androgen activity, is sometimes used if the effect is intolerable.
What potassium level should trigger holding the dose?
There's no single universal cutoff, and thresholds vary by institution and by the patient's baseline renal function, so always follow the specific protocol or prescriber order in front of you. As a general principle, a potassium above the lab's normal range, or any ECG change consistent with hyperkalaemia, warrants holding the dose and notifying the prescriber before the next one is due.
Is spironolactone safe in pregnancy?
Spironolactone's anti-androgen activity raises concern for feminisation of a male fetus, so it's generally avoided in pregnancy unless the benefit clearly outweighs the risk and no safer alternative exists. Confirm pregnancy status before starting and discuss contraception where relevant.
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