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Potassium-sparing diuretic / aldosterone antagonist

Spironolactone: uses, side effects & precautions

Also known as Aldactone, Verospiron, Spiractin.

This information is for general guidance only and does not constitute medical advice. Always consult a qualified healthcare professional for personal medical concerns. In an emergency, call your local emergency number.

What it is used for

  • Heart failure
  • High blood pressure, especially when other medicines are not enough
  • Fluid build-up (oedema) from heart, liver, or kidney conditions
  • Conditions with high aldosterone hormone levels

How it works

Spironolactone blocks the hormone aldosterone, helping the body remove extra salt and water while holding on to potassium. This lowers blood pressure and fluid overload and, in heart failure, helps protect the heart.

How it is taken

Taken by mouth as a tablet, and as an oral liquid in some countries, usually once or twice a day. Take it exactly as your doctor or pharmacist directs and follow the label. Your clinician will usually check your blood potassium and kidney function, as this medicine raises potassium.

No doses here on purpose. The right strength and schedule depend on you — only a doctor or pharmacist should set them. Always follow your prescription and the label.

Common side effects

  • Increased urination
  • Dizziness
  • Mild rise in blood potassium
  • Breast tenderness or enlargement (more often in men)
  • Menstrual changes in women
  • Stomach upset

Serious effects — get help

  • Signs of high potassium such as muscle weakness, numbness, or an irregular or slow heartbeat (seek urgent care)
  • Severe dizziness or fainting
  • Reduced urination or signs of kidney problems
  • Signs of a serious allergic or skin reaction

If a reaction is severe — for example trouble breathing, swelling of the face or throat, or collapse — go to the nearest emergency room now or call your local emergency number. Do not wait for an online consultation.

Interactions to watch

  • Potassium supplements and potassium-containing salt substitutes
  • ACE inhibitors and ARBs (added potassium rise)
  • Other potassium-sparing diuretics
  • Non-steroidal anti-inflammatory drugs such as ibuprofen
  • Lithium
  • Digoxin

Who should take care

  • Avoid potassium supplements and potassium-based salt substitutes unless advised
  • Tell your clinician about kidney disease — high potassium can be dangerous
  • Discuss pregnancy or breastfeeding with your doctor
  • Attend blood tests to monitor potassium and kidney function
  • Report muscle weakness, numbness, or an irregular heartbeat promptly

Frequently asked questions

How is spironolactone different from other water pills?
Unlike most water pills, it helps the body keep potassium rather than lose it. That is why your clinician monitors potassium and why you should avoid extra potassium unless advised.
Why am I told to avoid potassium?
Because this medicine raises potassium, adding more from supplements or salt substitutes can push levels too high, which can affect the heart. Always check first.
Can it cause breast changes?
Yes, breast tenderness or enlargement can occur, more often in men, because of its hormonal effects. Tell your clinician if this happens, as alternatives may exist.
Why do I need blood tests?
They check your potassium and kidney function so your clinician can keep the medicine safe for you.
Is Spironolactone safe to take?
For most people it is safe when taken exactly as a doctor or pharmacist advises and as printed on the label. Tell your clinician about your other medicines and health conditions, and seek urgent care for any serious reaction.

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