Quick answer

Ask your pharmacist or doctor before combining. Spironolactone makes the body hold on to potassium, and its label advises avoiding potassium supplements and potassium-rich salt substitutes, because the combination may lead to severely high blood potassium. The label also says to check potassium within 1 week of starting and regularly after that.^1,2

Key facts

The Aldactone label says that taking spironolactone with potassium supplements or drugs that raise potassium may lead to severe hyperkalemia.¹
For heart failure, the label says potassium supplements should generally be stopped when spironolactone is started.¹
NIH lists potassium-sparing diuretics such as spironolactone and amiloride among the medicines that can raise blood potassium.²
The label also lists low blood sodium and low magnesium among possible effects and advises checking electrolytes periodically.¹

Avoid the combination unless your doctor advises it

Spironolactone keeps potassium in the body. Its label says taking it with potassium supplements can lead to severe high potassium, and that patients should be advised to avoid potassium supplements and foods high in potassium, including salt substitutes.^1,2,3

On the medicine's label

Why spironolactone and potassium do not mix freely

Spironolactone blocks aldosterone, a hormone that tells the kidneys to trade potassium for sodium. With the hormone blocked, more sodium and water leave the body while potassium is kept. That is how the medicine works, and it is also why potassium from other sources can build up.¹

The label's counseling section is direct: people taking spironolactone should be advised to avoid potassium supplements and foods containing high levels of potassium, including salt substitutes. That is firmer than the ask-first wording on the losartan label.^1,4

MedlinePlus lists this class of medicine, and extra potassium from supplements or salt substitutes, among the causes of high blood potassium.^3,5

Who is most at risk

According to the label, the risk rises with poor kidney function and with other medicines that raise potassium, such as ACE inhibitors, angiotensin receptor blockers, some anti-inflammatory pain medicines and heparin.¹

Too much potassium from supplements or salt substitutes can raise blood potassium (hyperkalemia), especially with kidney disease or medicines that keep potassium in the body. It often causes no symptoms, but severe cases can cause dangerous heart rhythms.^2,5

Sodium and magnesium too

Potassium is not the only mineral the medicine moves. Its label says spironolactone can also lower blood sodium and magnesium, and advises checking electrolytes from time to time. NIH adds that potassium-sparing diuretics reduce the magnesium lost in urine, the opposite of loop and thiazide water pills.^1,6

None of that makes an electrolyte drink the answer. Which minerals you need, if any, depends on your blood tests, and that is a decision for whoever prescribes the medicine.

Questions for your pharmacist

Which of the products I use contain potassium, including salt substitutes and electrolyte drinks?
When are my next potassium and kidney blood tests?
Does my dose, or my kidney function, change the advice?
If I sweat heavily at work or in sport, what should I drink instead?

Questions people ask

Can I use a salt substitute while taking spironolactone?

The label advises against it. Many salt substitutes replace sodium with potassium chloride, and the Aldactone label names potassium-containing salt substitutes among the sources to avoid.^1,7

Do I need to avoid potassium-rich foods too?

The label's advice covers foods high in potassium as well as supplements. A medium banana has about 422 mg and a cup of cooked lentils about 731 mg, so ask your doctor or a dietitian how much potassium from food is right for you.^1,2

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.