Is potassium safe?

For healthy people with normal kidneys, potassium from food is not a health risk: the kidneys pass extra potassium into urine.^[1] Neither the US nor the EU has set an upper limit.^[1][2] EFSA, the EU food safety authority, looked at long-term use in healthy adults. About 3,000 mg a day as potassium chloride supplements, on top of food, caused no adverse effects.^[2] The risks are:

• Hyperkalemia. People with kidney disease, or who take ACE inhibitors, angiotensin receptor blockers (ARBs) or potassium-sparing diuretics, can get high blood potassium even from food.^[1] Severe cases can cause muscle weakness, paralysis and heart rhythm problems that can be life threatening.^[1]
• Very high doses. Case reports linked 5,000 to 7,000 mg a day from supplements to effects on the heart in apparently healthy adults.^[2]
• Stomach and gut. Supplements can cause minor stomach and gut side effects.^[1] Potassium salts in some medicines have been linked to injuries of the small bowel.^[1]
• Salt substitutes. One teaspoon can contain 440 to 2,800 mg of potassium.^[1]

People with kidney disease, heart failure, type 1 diabetes or liver disease, and people who take blood pressure medicines or diuretics, should ask a doctor or pharmacist first.^[1]