Spironolactone — Diuretic & Hormone Guide | KiwiMeds
✅ Reviewed by a Registered Pharmacist NZ | Last updated: May 2026 | This information is for educational purposes only and does not replace advice from your doctor or pharmacist.
What is spironolactone?
Spironolactone is a potassium-sparing diuretic with anti-androgen properties. It is used to treat high blood pressure, heart failure, fluid retention, and hormonal conditions such as PCOS (polycystic ovary syndrome). It is also used off-label for acne and gender-affirming hormone therapy.
What is it used for? (NZ context)
Spironolactone treats fluid retention (oedema), primary hyperaldosteronism, heart failure, and high blood pressure. In women, it is also used for PCOS-related acne, hirsutism (excess hair growth), and hormone management. It is funded by Pharmac for its approved indications.
How does it work?
Spironolactone blocks aldosterone receptors in the kidney, reducing sodium and water retention while keeping potassium. It also blocks androgen (male hormone) receptors throughout the body, which is why it helps with acne and excess hair in conditions like PCOS.
How to take it
Take spironolactone with food to reduce stomach upset. Avoid high-potassium foods (bananas, salt substitutes) and potassium supplements unless advised by your doctor. Your potassium levels will be monitored with blood tests, especially when starting.
Common side effects
- Increased urination (especially at start)
- Dizziness or lightheadedness
- Breast tenderness or enlargement (gynaecomastia in men)
- Menstrual irregularities in women
- Nausea
Serious side effects to watch for
Hyperkalaemia (high potassium) is the main serious risk — symptoms include muscle weakness, irregular heartbeat. Regular blood tests are essential. Do not combine with other potassium-sparing medicines or high-dose potassium supplements without medical supervision.
Important drug interactions
ACE inhibitors and ARBs — significant risk of hyperkalaemia when combined; blood tests are essential. Potassium supplements — avoid unless prescribed. NSAIDs — may reduce effectiveness. Digoxin — spironolactone can affect digoxin levels.
NZ-specific information
Pharmac funding: Spironolactone 25mg and 100mg tablets are funded by Pharmac. It is available as a generic in NZ.
Frequently asked questions
Can spironolactone help with acne?
Yes — spironolactone is often prescribed off-label for hormonal acne in women, particularly when other treatments have not worked. It reduces the effect of androgens on skin oil production. It is not used for acne in men due to hormonal side effects.
Will spironolactone affect my periods?
Spironolactone can cause irregular periods or spotting, especially when first starting. Some women find their periods become lighter or stop. If you are sexually active and of childbearing age, discuss contraception with your doctor as spironolactone can potentially harm a male foetus.
Can I eat bananas on spironolactone?
Moderate amounts of high-potassium foods are generally fine, but avoid very large amounts of potassium-rich foods or salt substitutes (which contain potassium chloride). Your doctor will monitor your potassium with blood tests.
💬 Talk to your pharmacist or doctor for personalised advice about spironolactone.
Reviewed by a Registered Pharmacist NZ | BPharm, Pharmacy Council of New Zealand
References & Further Information
The following New Zealand and international resources were used to inform this page: