Potassium: Benefits, Dosage, and Safety

What potassium is

Potassium is an essential dietary mineral and the most abundant positively charged ion (cation) inside cells. It is naturally present in many foods, especially fruits, vegetables, legumes, dairy, and meats, and is also available as a dietary supplement and in potassium-based salt substitutes. About 90 percent of ingested potassium is absorbed, mostly by passive diffusion in the small intestine, and the kidneys are the main regulator of how much is retained or excreted. The intracellular concentration is roughly 30 times higher than the extracellular concentration, and this gradient, maintained by the sodium-potassium (Na+/K+) ATPase transporter, underlies nerve transmission, muscle contraction, and kidney function. Because most body potassium is inside cells, blood levels do not always reflect total body stores.

What it does

• Maintains intracellular fluid volume and normal cell tonicity, working in balance with sodium which governs extracellular fluid volume
• Helps maintain the transmembrane electrochemical gradient (via the Na+/K+ ATPase) required for normal cell function
• Supports proper nerve transmission and signaling
• Supports normal muscle contraction, including cardiac muscle function
• Contributes to normal kidney function and, with adequate intake, to normal blood pressure regulation and urinary sodium excretion

How much potassium per day

These are population reference values from the NIH and the Dietary Reference Intakes. They are targets for healthy people, not personal prescriptions. The last column is the Tolerable Upper Intake Level, the most you should get from all sources combined.

Deficiency and who is at risk

Insufficient intake can raise blood pressure, kidney stone risk, bone turnover, urinary calcium excretion, and salt sensitivity. Severe deficiency causes hypokalemia (serum potassium below about 3.6 mmol/L). Mild hypokalemia signs include constipation, fatigue, muscle weakness, and malaise. Moderate to severe hypokalemia (below about 2.5 mmol/L) can cause polyuria, glucose intolerance, muscular paralysis, poor respiration, and cardiac arrhythmias, which can be life threatening. Hypokalemia is rarely caused by low dietary intake alone; it usually results from diarrhea, vomiting, refeeding syndrome, laxative or diuretic use, heavy sweating, or dialysis. Magnesium depletion can worsen and perpetuate hypokalemia.

Who may need more

• People with inflammatory bowel disease who lose potassium through chronic diarrhea
• People on potassium-wasting diuretics (thiazide or loop) who develop hypokalemia and whose clinician recommends supplementation
• People prone to calcium kidney stones, for whom clinicians may prescribe potassium citrate (a drug therapy, not self-treatment)
• Most people in the US, who consume less potassium than the AI and are encouraged to raise intake through potassium-rich foods rather than supplements

Food sources

Fruits and vegetables are excellent sources, along with legumes, potatoes, dairy, meats, poultry, fish, and nuts. High per-serving examples: dried apricots (755 mg per half cup), cooked lentils (731 mg per cup), mashed acorn squash (644 mg per cup), dried prunes (635 mg per half cup), raisins (618 mg per half cup), baked potato flesh (610 mg, 1 medium), canned kidney beans (607 mg per cup), orange juice (496 mg per cup), banana (422 mg, 1 medium), and 1% milk (366 mg per cup). Whole-wheat flour and brown rice contain much more potassium than their refined counterparts. The Daily Value (DV) for potassium is 4,700 mg.

Forms and absorption

In supplements potassium appears most often as potassium chloride, but also as potassium citrate, phosphate, aspartate, bicarbonate, and gluconate. Labels declare the amount of elemental potassium, not the weight of the whole compound. Most potassium-only supplements and multivitamins are limited to 99 mg per serving (about 2 percent of the Daily Value) because of FDA concerns that oral products over 99 mg potassium chloride have been linked to small-bowel lesions. Absorption is high: about 94 percent for potassium gluconate, similar to potassium from potatoes; liquid potassium chloride is absorbed within hours, while enteric-coated tablets are absorbed more slowly. Note that the food forms (phosphate, sulfate, citrate) differ from the potassium chloride used in salt substitutes and many supplements.

Safety, excess and interactions

Too much

In healthy people with normal kidney function, high dietary potassium does not pose a health risk because the kidneys excrete the excess, and there is no evidence it causes hyperkalemia or other adverse effects. The NASEM committee did not set a Tolerable Upper Intake Level (UL) for potassium. However, hyperkalemia (serum potassium above about 5.0 mmol/L) can occur in people with impaired potassium excretion, such as chronic kidney disease, or those taking ACE inhibitors or potassium-sparing diuretics, and also in people with type 1 diabetes, congestive heart failure, adrenal insufficiency, or liver disease. Very high amounts of potassium supplements or potassium-based salt substitutes can exceed the kidney's excretory capacity and cause acute hyperkalemia even in healthy individuals. Hyperkalemia can be asymptomatic but severe cases cause muscle weakness, paralysis, heart palpitations, paresthesias, and potentially life-threatening cardiac arrhythmias. Potassium salts in some medications have been linked to small-bowel lesions.

Interactions to know

• ACE inhibitors (e.g., benazepril/Lotensin) and angiotensin receptor blockers (ARBs, e.g., losartan/Cozaar): reduce urinary potassium excretion and can cause hyperkalemia; potassium status should be monitored, especially with other hyperkalemia risk factors such as impaired kidney function
• Potassium-sparing diuretics (e.g., amiloride/Midamor, spironolactone/Aldactone): reduce urinary potassium excretion and can cause hyperkalemia; monitoring is recommended, especially with impaired kidney function
• Loop diuretics (e.g., furosemide/Lasix, bumetanide/Bumex) and thiazide diuretics (e.g., chlorothiazide/Diuril, metolazone/Zaroxolyn): increase urinary potassium excretion and can cause hypokalemia; potassium status should be monitored and supplementation started if warranted
• Potassium-containing salt substitutes: add substantial potassium (about 440 to 2,800 mg per teaspoon) and can raise hyperkalemia risk in people with kidney disease or on potassium-retaining drugs

How status is measured

Status is not routinely assessed and is difficult to measure because most potassium is intracellular. Serum potassium (normal range about 3.6 to 5.0 mmol/L) is the common clinical test but correlates poorly with total tissue stores. Research methods include balance studies, total or exchangeable body potassium measurement, and tissue (e.g., muscle biopsy) analysis, all with limitations.

Regulated as a dietary supplement ingredient under DSHEA, not FDA-approved to treat disease. The FDA Daily Value is 4,700 mg and potassium is now mandatory on the Nutrition Facts label. Many products are limited to 99 mg per serving for safety reasons, and FDA requires some oral drugs providing more than 99 mg potassium to carry a small-bowel-lesion warning. FDA has approved the qualified health claim that diets containing good sources of potassium and low in sodium may reduce the risk of high blood pressure and stroke.

What the evidence supports

We grade the strength of evidence behind each common reason people take potassium, mirroring how the NIH describes it.