Spironolactone side effects — what you need to know

Spironolactone is useful for blood pressure, heart failure, and hormonal issues like acne or hirsutism. But it can cause side effects — some small and manageable, some that need quick attention. The biggest safety issue is higher potassium in your blood (hyperkalemia). That can be quiet at first and suddenly dangerous.

This guide tells you the side effects you’ll most often see, what signs mean urgent care, and simple steps to reduce risk. No fluff — practical tips you can use before and during treatment.

Common and dose-related side effects

Some effects happen more often and usually aren’t life-threatening. Expect things like increased urination, dizziness (especially standing up), stomach upset or diarrhea, and breast tenderness or swelling. Women can notice irregular periods. Men can get breast enlargement (gynecomastia) or reduced libido — these often improve after stopping or lowering the dose.

Fatigue and mild lightheadedness are common when your body adjusts. These often get better in a few days to weeks. If you’re taking a low dose for acne, side effects tend to be milder than with higher doses used for heart failure.

Serious risks and how to spot them

Hyperkalemia is the most serious risk. Signs include muscle weakness, numbness or tingling, feeling that your heart is skipping beats, or sudden severe fatigue. If you feel any of those, get medical help right away — high potassium can cause dangerous heart rhythm problems.

Kidney function can drop while on spironolactone. Watch for reduced urine output, swelling that gets worse, or sudden weight gain. Severe allergic reactions (rash, swelling of face or throat, trouble breathing) are rare but need immediate emergency care.

Interactions raise risks. Avoid taking spironolactone with potassium supplements, potassium-based salt substitutes, ACE inhibitors or ARBs without close monitoring, and some NSAIDs. Tell your prescriber about herbal supplements and all meds you use.

Simple safety steps: check blood tests. Your doctor should measure potassium and kidney function before you start, soon after starting or changing dose (within a week or two), and periodically after that. Don’t add potassium supplements or high-potassium salt substitutes unless a clinician tells you it’s safe.

Avoid if pregnant or planning pregnancy — spironolactone can affect a male fetus. If you’re breastfeeding, talk to your provider about risks and alternatives.

Bottom line: spironolactone helps a lot of people, but it’s a drug you monitor. Know the common side effects, watch for signs of high potassium or kidney trouble, and keep up with labs. If anything feels off, call your prescriber — quick action prevents most serious problems.