Can you have too many electrolytes?

Potassium

Normal blood potassium is about 3.6 to 5.0 mmol/L, and a level above 5.0 is called hyperkalemia.^[1] In healthy people, the kidneys pass extra potassium from food into urine. No upper limit is set.^[1] In healthy people, potassium supplements of up to 15,600 mg a day for 5 days raised blood potassium, but it stayed in the normal range.^[1] Very large amounts of supplements or potassium salt substitutes can still go beyond what the kidneys can remove, even in healthy people.^[1]

The risk is higher with these conditions and medicines:^[1]

• chronic kidney disease^[1]
• ACE inhibitors, angiotensin receptor blockers and potassium-sparing diuretics^[1]
• type 1 diabetes, heart failure, adrenal insufficiency and liver disease^[1]

Too much potassium in the blood (hyperkalemia) can cause muscle weakness, paralysis, palpitations, tingling and a dangerous heart rhythm.^[1] Potassium supplements can also upset the stomach. Potassium salts in some medicines have caused damage to the small bowel, so most potassium-only supplements contain up to 99 mg.^[1]

Magnesium

The US upper limit for magnesium from supplements is 350 mg a day for adults, 110 mg for children aged 4 to 8 and 65 mg for children aged 1 to 3. Higher doses often cause diarrhea, nausea and stomach cramps.^[2] Doses above 5,000 mg a day from laxatives or antacids have caused magnesium poisoning: low blood pressure, vomiting, an irregular heartbeat and cardiac arrest. Poor kidney function raises this risk.^[2]

Sodium

No upper limit is set for sodium. Very high amounts eaten at once have caused high blood sodium and death, but only in extreme cases.^[5] The main problem is the daily total. WHO advises adults to eat less than 2,000 mg a day, while the world average in 2021 was 4,278 mg. Too much sodium raises blood pressure and the risk of heart disease.^[3] The US Daily Value is less than 2,300 mg a day. Over 70% of the sodium in US diets comes from packaged and prepared foods, not from salt added in cooking or at the table.^[6]

Too much water

During long exercise, drinking too much water or dilute fluid can lower blood sodium. This can happen in as many as 2% to 7% of people in endurance events.^[4] The signs are bloating, vomiting, headache and confusion. A severe case is a medical emergency, and drinking to thirst helps prevent it.^[7]

Who should ask first

Some people should ask a doctor or pharmacist before they take electrolyte supplements. This applies to kidney disease, heart failure and liver disease, and to medicines that keep potassium in the body.^[1][2]