“Potassium supplements are dangerous.”
Over-the-counter potassium supplements are not dangerous for most healthy people, because healthy kidneys clear extra potassium.
A store-bought potassium pill is not a danger for most healthy people. The risk is real if your kidneys do not clear potassium well or you take medicines that make your body hold on to it, and salt substitutes can add far more potassium than a pill.
If you have kidney disease or take blood pressure or heart medicines, check with your pharmacist before using potassium pills or a potassium salt substitute.
Safety note: Too much potassium in the blood can cause muscle weakness and dangerous heart rhythm problems, sometimes with no warning signs. The risk is highest if your kidneys do not clear potassium well or you take medicines that hold on to it: ACE inhibitors, ARBs, or potassium-sparing water pills such as spironolactone, amiloride or triamterene. Prescription potassium tablets should be swallowed whole with a meal and a full glass of water, because they can injure the stomach and intestines.
Talk to a healthcare professional if: you have kidney disease, heart failure, type 1 diabetes, liver disease or adrenal insufficiency, or you take an ACE inhibitor, an ARB or a potassium-sparing water pill, and you are thinking about a potassium supplement or a potassium salt substitute; or you get severe vomiting, belly pain or black stools while taking prescription potassium.
Healthy kidneys clear extra potassium, store-bought pills often contain a small dose, and a very large trial of a potassium salt substitute found no rise in serious high-potassium problems. Confidence is Moderate because direct trials of supplement pills in healthy people are limited, and the real risks in some groups are well documented.
Over-the-counter potassium supplements are not dangerous for most healthy people, because healthy kidneys clear extra potassium. Very large amounts can still raise blood potassium too high, and strong prescription potassium tablets can irritate the gut.
In the US, many potassium supplements contain 99 mg or less per serving, a small amount. That is a common choice by makers, not a legal cap: they limit the amount because FDA has ruled that some potassium chloride drugs with more than 99 mg are not safe, since they were linked to sores in the small bowel. Some salt substitutes contain far more potassium than a pill, from about 440 to 2,800 mg per teaspoon. In a trial of 20,995 older adults in rural China with high blood pressure or a past stroke, villages that switched to a potassium salt substitute for about 5 years had fewer strokes, and serious problems from high potassium were about the same as with regular salt (3.35 vs 3.30 per 1,000 people per year). That trial left out people with known kidney disease or those taking potassium-sparing water pills or potassium supplements. No safe upper limit has been set for potassium from food.
- Office of Dietary Supplements, National Institutes of Health. Potassium: Fact Sheet for Health Professionals. Updated June 2, 2022
- Neal B, Wu Y, Feng X, et al. Effect of salt substitution on cardiovascular events and death. New England Journal of Medicine. 2021;385(12):1067-1077. DOI: 10.1056/NEJMoa2105675. PMID: 34459569
- AbbVie. K-TAB (potassium chloride extended-release tablets) prescribing information. Revised April 2018