Can too much potassium be dangerous?

With healthy kidneys

In healthy people with normal kidneys, a high potassium intake from food is not a health risk, because the kidneys remove the extra in urine.^[1] The US National Academies (NASEM) found no evidence that high intakes cause hyperkalemia in adults with normal kidneys, and did not set an upper limit. Case reports of heart problems and death from very large doses of supplements were not enough to set one.^[1] EFSA, the EU food safety authority, did not set one either.^[2]

• Up to 15,600 mg a day of supplements for 5 days raised blood potassium in healthy people, but not above the normal range.^[1]
• About 3,000 mg a day as potassium chloride supplements, on top of food, caused no adverse effects in healthy adults over the long term.^[2]
• Food intakes up to 5,000 to 6,000 mg a day carry a low risk for healthy adults.^[2]
• Case reports linked 5,000 to 7,000 mg a day from supplements to effects on the heart in apparently healthy adults.^[2]

Very large amounts of supplements or salt substitutes can be more than the kidneys can remove, and cause sudden hyperkalemia even in healthy people.^[1]

Who is at risk

In these people, even food below the adequate intake can cause hyperkalemia:^[1]

• people with chronic kidney disease^[1]
• people who take ACE inhibitors, such as benazepril, or angiotensin receptor blockers (ARBs), such as losartan, which lower the potassium the kidneys pass into urine^[1]
• people who take potassium-sparing diuretics, such as amiloride or spironolactone^[1]

Hyperkalemia can also occur with type 1 diabetes, heart failure, adrenal insufficiency and liver disease.^[1] People at risk should ask a doctor or dietitian how much potassium to get from all sources.^[1]

Signs of hyperkalemia

The normal blood level is about 3.6 to 5.0 mmol/L, and hyperkalemia means a level above 5.0.^[1] It can cause no symptoms. Severe cases can cause muscle weakness, paralysis, a pounding heart and a burning or prickling feeling in the hands and feet. They can also cause heart rhythm problems that can be life threatening.^[1]

Stomach and gut

Potassium supplements can cause minor stomach and gut side effects.^[1] EFSA notes that these depend more on the type of tablet, such as slow-release wax-matrix tablets, than on the dose.^[2] Potassium salts in some medicines have been linked to injuries of the small bowel, with blockage, bleeding and perforation. The FDA requires a warning on some potassium medicines with more than 99 mg.^[1]

What trials found

In a 2013 review of trials, more potassium had no adverse effect on kidney function, blood fats or stress hormones (catecholamines) in adults.^[3] In a trial of 20,995 people, serious events from high blood potassium were as common with a potassium salt substitute as with regular salt (3.35 and 3.30 per 1,000 person-years).^[4] The trials in a 2022 Cochrane review left out people for whom more potassium is known to be harmful.^[5]

Medicines that lower potassium

Loop diuretics, such as furosemide and bumetanide, and thiazide diuretics, such as chlorothiazide and metolazone, raise potassium losses in urine and can cause a low level (hypokalemia).^[1] Experts advise checking potassium levels in people who take them.^[1]

Anyone who takes a medicine every day, or has kidney, heart or liver disease, should ask a doctor or pharmacist before taking potassium.^[1]