Potassium

Potassium is an essential mineral. It is the most abundant positively charged ion inside your cells, says the NIH (the US National Institutes of Health). An adult body holds about 140 g of it (for a 175-pound adult).

Cells keep about 30 times more potassium inside than outside. That difference, held up by the sodium-potassium pump, is what nerve signals, muscle contraction and kidney function run on. Potassium also works against sodium. The NIH says higher intakes may lower blood pressure in part by widening blood vessels and increasing the sodium lost in urine.

Here is the part most people do not know: the official US target was cut in 2019. In 2005 the Institute of Medicine had set an adequate intake (an amount assumed to be enough) of 4,700 mg a day. In 2019 a National Academies committee replaced it with 3,400 mg for men and 2,600 mg for women. It based them on the highest median intakes seen in healthy people.

The Daily Value on US food labels is still 4,700 mg. So a food can show a lower percentage on its label than it would against the current intake target.

Most people eat less than these targets. In US survey data from 2013 to 2014, men aged 20 and older averaged 3,016 mg of potassium from food, and women 2,320 mg. EFSA (the EU’s food safety agency) reports that average adult intakes in eight EU national surveys ranged from 2,463 to 3,991 mg a day.

A low level of potassium in the blood is a different matter. It rarely comes from diet alone and usually follows diarrhea, vomiting or certain drugs. The opposite problem matters too. People with kidney disease or on some blood pressure medicines can build up potassium, so general advice does not fit everyone.

Health benefits of potassium

• ★★★Lower blood pressurePotassium pills lowered the top number by about 3 points (3.11 mm Hg systolic) across 33 trials. In people with high blood pressure it fell more (4.48 mm Hg systolic), and a 22-trial review saw no drop in people without it.
• ★★★Salt substitutes with potassium lowered blood pressureSalt substitutes, with some sodium swapped for potassium, lowered the top number by about 5 points (4.76 mm Hg systolic) across 26 trials. In a rural China trial (past stroke, or age 60+ with high blood pressure), strokes were 0.86 times as common, but sodium fell too.
• ★★Fewer kidney stones with citrate saltsIn 7 small trials, new kidney stones were 0.26 times as likely on citrate salts such as potassium citrate. The benefit is attributed to the citrate, not to potassium itself.
• ★★Lower blood pressure on the DASH dietThe DASH diet, rich in fruits, vegetables and low-fat dairy, lowered blood pressure by 5.5/3.0 mm Hg (top/bottom number) against a typical American diet. It also cut fat and raised magnesium and calcium, so potassium alone cannot get the credit.
• ★★Mixed results for bone densityPotassium citrate raised lower-spine bone density by 1.7% more than placebo in adults over 65 (24 months). It did not help women aged 55 to 65, and a review of 14 studies found no effect on bone density.

Foods high in potassium

Potassium is found in a wide range of plant and animal foods. Beans and potatoes lead our USDA ranking per serving. Adzuki beans have 1,224 mg per cup, 26% of the 4,700 mg Daily Value. Lima beans (955 mg per cup) and a medium potato (905 mg) follow.

Per 100 g, dense foods lead: cocoa powder (1,524 mg), hemp seeds (1,200 mg) and pistachios (1,025 mg). Flaxseeds and pumpkin seeds come next, though people eat these in small amounts. Per 100 kcal, leafy greens and herbs lead, with spinach at 2,426 mg. The ranking below has the full list.

Bananas are a popular reference food, but a medium one has 422 mg (9% of the Daily Value), according to the NIH. It is not in the top 10 of any of our rankings. The NIH adds dried apricots at 755 mg per half cup, orange juice at 496 mg per cup and baked potato flesh at 610 mg.

Among US adults, the top sources are milk, coffee, tea, other nonalcoholic drinks and potatoes. Refining removes potassium: a cup of cooked brown rice has 154 mg, against 54 mg for white rice. Potassium also leaches into cooking water.

In a lab study of root vegetables, boiling, rinsing and boiling again removed more potassium than boiling once, and soaking removed little. But most roots kept a moderate or high amount. That matters for people told to limit potassium, who should follow their care team’s advice.

How potassium works

The biochemistry below is well established. But it comes from reviews, balance studies and animal work rather than from trials of extra potassium in people. Four ideas cover most of it.

Potassium sets up the electrical charge across every cell membrane. The gut absorbs nearly all of what you eat, and the kidneys decide how much stays. And potassium and sodium pull blood pressure in opposite directions. Then comes what has been seen in people.

It builds the charge across every cell membrane

Potassium is the most abundant cation (positive ion) inside cells. The NIH says its concentration there is about 30 times higher than outside. The sodium-potassium ATPase pump keeps that gradient up, and the gradient is required for nerve transmission, muscle contraction and kidney function.

A review adds that it sets the cell’s membrane potential (its electrical charge). That is why potassium matters for nerve impulses and for the beat of heart, skeletal and smooth muscle.

The gut absorbs about 90% of it

Potassium moves across the wall of the small intestine by passive diffusion, and the NIH and EFSA both put absorption at about 90%. A balance study followed 28 adults eating their usual food for a year. It found 85% apparent absorption, which did not change over a wide range of intakes. Most of what is absorbed leaves in the urine: 77% of intake on average.

The forms differ a little. A review of potassium chloride studies puts absorption at 70% to 90%, fast from liquids and slow from solid tablets. A later trial found more than 94% absorbed from both potassium gluconate and potatoes. The potassium in fruits and vegetables comes as phosphate, sulfate, citrate and other salts, not as chloride, says the NIH.

The kidneys decide how much stays

The kidneys adjust potassium excretion to intake, which is how long-term balance is kept. Excretion climbs quickly after a potassium-rich meal unless body stores are depleted. The NIH says the kidneys still pass at least 5 mmol (about 195 mg) a day. So balance cannot be reached below roughly 400 to 800 mg a day.

Normal blood potassium is about 3.6 to 5.0 mmol/L (a unit of concentration in blood). Because most potassium is inside cells, a blood test can correlate poorly with tissue stores. EFSA found no suitable marker of potassium status for setting intake values. Risk climbs on both sides of the normal range: in 27 cohorts, death was most likely at either end.

Potassium and sodium pull blood pressure in opposite directions

Part of the answer sits in the kidney. In experiments in mice and cultured cells, a diet short of potassium switched on a salt transporter called NCC. NCC sits in the distal (far) part of the kidney tubule, and this happened even on a high-salt diet. The kidney then held on to sodium, and blood pressure rose.

The effect depended on the level of potassium in the blood, which changes the voltage across the tubule cells and the chloride inside them. The authors say this keeps potassium in the body at the price of higher pressure.

In people, the same pairing shows up in surveys. In the PURE study, only 0.002% of participants met both the sodium and potassium targets. Higher potassium excretion blunted the extra risk linked with high sodium.

What has been seen in people

The clearest human findings are about blood pressure and the form of the potassium. Trials of extra potassium lower pressure by about 3 to 4 mm Hg. The biggest drops are in people with high blood pressure, high sodium intakes and low starting potassium.

Potassium-enriched salt substitutes lowered pressure by about 4.6 to 4.8 mm Hg in meta-analyses. In one large trial they lowered stroke and death too, but they also cut sodium. Cohort studies agree, with the lowest stroke risk near 90 mmol (about 3,500 mg) a day.

For bone and kidney stones, alkaline salts matter more than potassium itself. All of these are among the study cards above.

How much potassium do you need?

Adults need 2,600 to 3,400 mg of potassium a day, according to the US adequate intake. That is 3,400 mg for men and 2,600 mg for women aged 19 and older. EFSA’s adequate intake in the EU is 3,500 mg a day for adult men and women.

These are adequate intakes, not recommended allowances. The US committee found the evidence too thin to set an average requirement, and it set no upper level. So neither number is a precise need. The values do not apply to people whose kidneys or medicines limit potassium excretion.

Pregnancy raises the US value to 2,900 mg a day for ages 19 to 50 (2,600 mg at ages 14 to 18). Breastfeeding raises it to 2,800 mg (2,500 mg at ages 14 to 18). EFSA keeps 3,500 mg in pregnancy, because the body adapts to cover the extra need. It sets 4,000 mg while breastfeeding, to replace the roughly 400 mg lost in breast milk.

For older adults, the US values stay at 3,400 mg for men and 2,600 mg for women from age 51. EFSA gives one adult value from age 18, with no separate one for older people.

Potassium deficiency: signs and who is at risk

Low blood potassium is called hypokalemia, and it means a level below about 3.6 mmol/L. Mild cases cause constipation, fatigue, muscle weakness and a general unwell feeling, says the NIH. Below about 2.5 mmol/L, it can cause large volumes of dilute urine, glucose intolerance, muscle paralysis, poor breathing and abnormal heart rhythms.

This is especially so in people with heart disease, and severe cases can be life-threatening. Hypokalemia affects up to 21% of hospitalized patients, usually through diuretics (water pills) and other drugs. It is rare in healthy people with normal kidneys.

Low diet alone is rarely the cause. The usual causes are diarrhea, vomiting, laxative misuse and diuretics such as thiazides and loop diuretics, the NIH says. Others are eating clay, heavy sweating, dialysis and refeeding after starvation.

Low magnesium can also push potassium out through the kidneys. More than half of the people with clinically significant hypokalemia may be short of magnesium.

Some people are more likely to fall below the adequate intake while staying above the amount needed to prevent hypokalemia. They include people with Crohn’s disease or ulcerative colitis, regular users of some diuretics or large doses of laxatives, and people with pica (craving non-foods). Low potassium intakes can also raise blood pressure, kidney stone risk, bone turnover and salt sensitivity.

Doctors test serum potassium. But because most potassium sits inside cells, the result can correlate poorly with tissue stores, so a result needs a doctor’s reading.

Forms of potassium: absorption and effects

Potassium supplements and potassium-enriched foods use different compounds. Potassium chloride is the most common, but citrate, phosphate, aspartate, bicarbonate and gluconate are also sold, says the NIH. They differ in how much potassium they hold by weight, whether they are alkaline, and how fast they release in the gut.

The label must show elemental potassium (the potassium itself), not the weight of the whole compound. By weight, potassium is about 17% of potassium gluconate and about 52% of potassium chloride.

The honest bottom line: absorption is not the main difference, because every form studied is absorbed well. What differs is the partner ion. In head-to-head trials, potassium chloride, citrate and bicarbonate lowered blood pressure about equally.

The alkaline salts (citrate and bicarbonate) lowered urinary calcium, and chloride did not. The bone and kidney stone trials that worked used citrate or bicarbonate. For solid potassium chloride tablets, the issue is safety: wax-matrix tablets caused more gut lesions in a trial. US rules require a warning on some tablets.

The blood pressure trials in the benefits section mostly used potassium chloride. The SSaSS salt substitute was potassium chloride mixed with sodium chloride. The stone trial used potassium citrate wax-matrix tablets, and the bone trials used citrate or bicarbonate. We found no trial that compared forms for muscle cramps or exercise, and no human absorption comparison for aspartate or phosphate.

Form	Share of the mineral by weight	What studies show	Source
Potassium chloride	About 52%	The form in most blood pressure trials and in salt substitutes. Absorbed 70% to 90% in a review: fast from liquids, slowly from solid tablets. Lowered blood pressure about as much as citrate and bicarbonate, but did not lower urinary calcium, and lost bone against citrate over 12 months in one trial. Wax-matrix tablets caused more upper gut lesions than a microencapsulated form, and a US rule requires a small-bowel warning on some tablets.	1, 3, 4, 5, 7, 8, 9, 12, 14, 15, 16
Potassium citrate	About 38% (tripotassium citrate)	An alkaline salt. Lowered blood pressure about as chloride did. Raised bone density in two of three trials, not in 276 women over 2 years. Cut new kidney stones in small trials, a benefit the NIH attributes to the citrate. In a single-dose trial more went into red blood cells and urine than with chloride.	1, 4, 7, 9, 10, 12, 13, 17, 18, 19, 20
Potassium bicarbonate	About 39%	An alkaline salt. At 81 and 122 mmol a day it lowered a bone-breakdown marker and urinary calcium in 244 adults, and it improved blood vessel function as chloride did. We found no bone density or fracture trial.	4, 8, 11, 16
Potassium gluconate	About 17%	About 94% absorbed, as well as potassium from potatoes, in 35 healthy adults. We found no trial of it for blood pressure, bone or kidney stones.	1, 4, 6
Phosphate and aspartate	Not stated	The NIH lists them among supplement forms. We found no human absorption comparison or outcome trial.	1
Salt substitutes (potassium chloride blends)	Not stated for products; the trial blends were 25% potassium chloride	Products hold 440 to 2,800 mg of potassium per teaspoon. Trial blends lowered blood pressure and, in SSaSS, stroke and death, but they also cut sodium. The NIH says people with kidney disease or on certain medicines should ask first.	1, 21
Food (fruits, vegetables, potatoes)	Not applicable	About 85% to 90% absorbed. The forms in produce are phosphate, sulfate, citrate and others, not chloride. Extra potassium from fruit and vegetables did not lower blood pressure in a trial of early hypertension.	1, 2, 6, 10

Here are the head-to-head and form-specific studies, strongest evidence first, 10 in all.

Is potassium safe? Supplements, dose and interactions

Potassium from food is not a safety concern for healthy people with normal kidneys, because the kidneys remove the excess, says the NIH. There is no tolerable upper intake level (UL, a likely-safe daily maximum) in the US or the EU. The National Academies committee decided that case reports of very large supplement doses were not enough evidence to set one. EFSA did not set one either.

EFSA considered food intakes of up to 5,000 to 6,000 mg a day low risk for healthy adults. In healthy adults, about 3,000 mg a day of potassium chloride supplements on top of food had no long-term adverse effects, it noted. It also notes case reports of heart effects at 5,000 to 7,000 mg a day of supplemental potassium.

No upper level does not mean no limit. The intake values do not apply to people with kidney disease or on medicines that hold potassium.

• Kidney disease and high potassium. In people whose kidneys, or medicines, limit potassium excretion, even intakes below the adequate intake can cause hyperkalemia, the NIH says. Heart failure, type 1 diabetes, adrenal insufficiency and liver disease also raise the risk. Symptoms are muscle weakness, tingling, palpitations and, in severe cases, dangerous heart rhythms, though mild cases can show no symptoms. In 191 people with stage 3b to 4 kidney disease, 2 weeks of 40 mmol of potassium chloride a day caused hyperkalemia in 11%.
• Medicines. ACE inhibitors (such as benazepril) and angiotensin receptor blockers (such as losartan) reduce potassium excretion. So do potassium-sparing diuretics such as amiloride and spironolactone. Loop and thiazide diuretics lower potassium and can cause hypokalemia. In Ontario, hospital admissions for hyperkalemia rose from 2.4 to 11.0 per 1,000 older heart-failure patients on ACE inhibitors once spironolactone use rose. Experts recommend monitoring potassium on these drugs.
• Salt substitutes. Many replace part of the sodium chloride with potassium chloride, at 440 to 2,800 mg of potassium per teaspoon, says the NIH. In the large SSaSS trial, serious events attributed to hyperkalemia were not clearly higher. In the Cochrane review, hyperkalemia showed little to no difference, but all 26 trials excluded people in whom extra potassium could be harmful. A 2024 review of guidelines proposed recommending potassium-enriched salt to people with high blood pressure. The exceptions would be people with advanced kidney disease, those taking a potassium supplement or a potassium-sparing diuretic, and anyone with another reason not to. Its authors include the lead author of the SSaSS trial. Ask a doctor first if you are in any of those groups.
• Why potassium pills are small. The NIH says most potassium-only supplements provide up to 99 mg (about 2% of the Daily Value) and multivitamins about 80 mg. Makers keep to 99 mg because of an FDA ruling, made after reports of small-bowel lesions. It found some oral drug products with potassium chloride above that amount not safe. The FDA also requires a warning on some potassium salt tablets, and has made no ruling on whether supplements above 99 mg need a warning. Its warning text for coated potassium tablets describes narrowing of the small bowel, with or without ulcers. This caused obstruction, bleeding and perforation, with surgery often needed and deaths reported. It adds that the incidence is low and that a causal link in people is not definitely established. EFSA says gut symptoms depend more on the formulation (slow-release and wax-matrix tablets) than on the dose.
• Higher doses and very large doses. Higher-dose potassium is a medicine, given with monitoring. The NIH says very high amounts of supplements or salt substitutes can exceed the kidney’s capacity and cause acute hyperkalemia even in healthy people. It adds that doses of up to 15,600 mg for 5 days in healthy people raised blood potassium, but not beyond the normal range. Potassium supplements can also cause minor stomach and bowel upset.

How to get more potassium

• Best foods. Beans and potatoes give the most per serving in our ranking. Adzuki beans have 1,224 mg per cup, lima beans 955 mg and a medium potato 905 mg. The NIH adds dried apricots at 755 mg per half cup and orange juice at 496 mg per cup.
• Food over pills. The potassium in potatoes was absorbed as well as potassium gluconate. The DASH diet, rich in fruits, vegetables and low-fat dairy, lowered blood pressure by 5.5/3.0 mm Hg more than a typical American diet. Keep grains whole: cooked brown rice has 154 mg per cup, against 54 mg for white rice.
• Pair it with less sodium. In pooled cohorts, the top quarter for the sodium-to-potassium ratio had a hazard ratio of 1.62 for cardiovascular events. A potassium-enriched salt substitute is one way to lower sodium, if your doctor agrees and you have healthy kidneys.

Frequently asked questions about potassium

Does potassium lower blood pressure?

A little, mostly in people who already have high blood pressure. Meta-analyses of trials found systolic pressure 3.11 mm Hg lower in 33 trials and 3.49 mm Hg lower in 22 trials. It was 4.48 mm Hg lower in people with high blood pressure, and the 2013 review saw no drop in people without it. A dose-response analysis found the benefit weakened above a 30 mmol rise in excretion and reversed near 80 mmol, so more is not better. Food counts too: the DASH diet cut pressure 5.5/3.0 mm Hg, but it changed many nutrients at once.

Do bananas have the most potassium?

No. A medium banana has 422 mg, 9% of the Daily Value, according to the NIH. It is a good everyday source but not in the top 10 of any of our rankings. Per serving, adzuki beans (1,224 mg per cup), lima beans (955 mg per cup) and a medium potato (905 mg) are higher. So are lentils (731 mg per cup) and dried apricots (755 mg per half cup, from the NIH).

Are potassium-enriched salt substitutes safe?

For most people with high blood pressure and healthy kidneys they appear to be, but not for everyone. In the SSaSS trial of 20,995 people, serious events attributed to hyperkalemia were not clearly higher (3.35 against 3.30 per 1,000 person-years). The Cochrane review found little to no difference in hyperkalemia, but all 26 of its trials excluded people in whom extra potassium could be harmful. The NIH says people with kidney disease or on certain medicines should ask a health care provider first. Products hold 440 to 2,800 mg of potassium per teaspoon.

Are potassium supplements safe?

Over-the-counter potassium pills are small, usually up to 99 mg, which is about 2% of the Daily Value, so they add little to a diet. The NIH says makers keep to that amount because of FDA rulings on potassium chloride drug products and small-bowel lesions. Higher doses are medicines. Very high amounts can cause dangerous hyperkalemia even in healthy people. The risk is far higher with kidney disease or with ACE inhibitors, angiotensin receptor blockers or potassium-sparing diuretics. Talk to a doctor before taking higher-dose potassium.

Who should limit potassium?

People whose kidneys or medicines limit potassium excretion may be told to limit it. The NIH names chronic kidney disease, ACE inhibitors and potassium-sparing diuretics as raising the risk of hyperkalemia. It also names type 1 diabetes, heart failure, adrenal insufficiency and liver disease. In a trial in stage 3b to 4 kidney disease, 11% developed hyperkalemia on 40 mmol a day of potassium chloride. Those people were older and had higher starting potassium. Limits are individual, so ask your care team before changing your diet.

Which potassium supplement is best?

No form has been shown best for health. Every form studied is absorbed well, and chloride, citrate and bicarbonate lowered blood pressure about equally in head-to-head trials. For bone and kidney stones, the trials that worked used citrate or bicarbonate, which are alkaline, while chloride did not lower urinary calcium. Wax-matrix chloride tablets caused more gut lesions in one trial. Read the elemental potassium on the label; the NIH says a typical supplement has up to 99 mg.

Does potassium help muscle cramps?

We found no randomized trial showing that potassium supplements relieve cramps in people with normal blood potassium. Low blood potassium can cause muscle weakness, and severe cases can cause paralysis, says the NIH. But it usually follows diarrhea, vomiting or diuretics rather than a low diet. If you get frequent cramps, a doctor can check your blood level, which is normally 3.6 to 5.0 mmol/L, instead of guessing.

Can potassium prevent kidney stones?

Possibly, but the evidence is mixed. Higher dietary potassium went with fewer stones in three large US cohorts (hazard ratios 0.44 to 0.67). Potassium citrate cut new stones in small trials (0.26 times the risk across 7 trials). The NIH says citrate, not potassium itself, probably does the work, and EFSA says an independent effect of potassium cannot be shown from the trials. If you have had stones, ask your doctor before taking any citrate.