Potassium

How much you need

The official Adequate Intake for adults, per day:

These are Adequate Intakes, based on the highest median intakes in healthy people. They do not apply to people whose kidneys excrete potassium poorly, because of kidney disease or medicines. Food labels calculate % Daily Value from 4,700 mg, more than these amounts.

People aged 18 fall in the official 14–18 group — 3,000 mg a day for males and 2,300 mg for females, 2,600 mg in pregnancy and 2,500 mg when breastfeeding. There is no upper limit at any age. Pregnancy and breastfeeding change what you need — confirm yours with your midwife, obstetrician or doctor.

Upper limit

No upper limit does not mean safe for everyone. If you have kidney disease, or take an ACE inhibitor or a potassium-sparing diuretic, even ordinary amounts — below the recommended intake — can raise blood potassium to dangerous levels, and angiotensin receptor blockers can raise it too. Talk to your doctor before taking a potassium supplement or using a salt substitute.

No upper limit has been set for potassium, because in healthy people with normal kidney function the kidneys remove the excess, and there is no evidence that high intakes cause harm. Case reports describe heart problems and death from very large doses of supplements, but the National Academies judged them insufficient to set a limit.

What it does

Potassium is present in every tissue and is needed for normal cell function, because it maintains the fluid volume inside cells and the electrical gradient across their membranes ^[1]. That gradient is required for nerve transmission, muscle contraction and kidney function ^[1]. Potassium is closely linked with sodium, the main regulator of fluid outside cells ^[1].

Forms

Fruits and vegetables contain potassium as phosphate, sulfate, citrate and other forms, but not as potassium chloride, the form used in salt substitutes and many supplements ^[1]. Most supplements contain no more than 99 mg — about 2% of the Daily Value — because the FDA has linked some potassium chloride drugs above that amount to small-bowel lesions ^[1]. Salt substitutes vary widely, from about 440 to 2,800 mg per teaspoon ^[1].

Where it comes from

1. Apricots, dried½ cup755 mg
2. Lentils, cooked1 cup731 mg
3. Squash, acorn, mashed1 cup644 mg
4. Prunes, dried½ cup635 mg
5. Raisins½ cup618 mg

How these five were chosen: The five foods with the most potassium per serving in the NIH fact sheet's food table. Fortified foods are marked.

Getting the most from it

The body absorbs about 85% to 90% of the potassium in food ^[1]. Whole-wheat flour and brown rice contain much more than white flour and white rice ^[1]. Milk, coffee, tea, other nonalcoholic drinks and potatoes are the top sources for U.S. adults ^[1].

In the United States

Americans consistently eat less potassium than recommended, and the Dietary Guidelines name it a nutrient of public health concern ^[1]. In 2013–2014, average intake from food was 3,016 mg a day for men and 2,320 mg for women ^[1]. About 12% of people take a supplement containing potassium, but it adds an average of only 87 mg a day ^[1].

Who is most likely to run low

• People with inflammatory bowel disease, such as Crohn's disease or ulcerative colitis ^[1]
• People taking certain diuretics, such as thiazides, or using large doses of laxatives or repeated enemas ^[1]
• People with pica who eat clay, which binds potassium in the gut ^[1]

What deficiency looks like

Too little potassium can raise blood pressure, kidney stone risk, bone turnover, calcium loss in urine and salt sensitivity ^[1]. Severe deficiency causes hypokalemia — rare in healthy people with normal kidney function, but found in up to 21% of hospital patients, usually because of diuretics and other medicines ^[1]. Mild hypokalemia causes constipation, fatigue, muscle weakness and malaise; severe hypokalemia can cause paralysis, poor breathing and dangerous heart rhythms ^[1]. It rarely comes from diet alone, more often from diarrhea, vomiting, laxative misuse, diuretics or heavy sweating, and magnesium depletion can contribute ^[1].

What the evidence supports, and what it doesn't

Established. Potassium is essential for nerve transmission, muscle contraction and kidney function ^[1]. The FDA allows the health claim that diets containing foods that are good sources of potassium and low in sodium may reduce the risk of high blood pressure and stroke ^[1].

Not supported by trials. In 2019, the National Academies found the evidence insufficient to set an intake of potassium for reducing the risk of chronic disease ^[1]. A Cochrane review of the six highest-quality trials found no significant reduction in blood pressure from potassium supplements ^[1].

Mixed. Blood pressure: other meta-analyses find that supplements, mostly potassium chloride, lower blood pressure — most in people with high blood pressure, with no significant effect in those without it ^[1]. Some of the benefit of potassium salt substitutes may come from the sodium they replace ^[1]. Stroke: in a meta-analysis of 11 cohort studies in 247,510 adults, 1,640 mg a day more potassium was linked to a 21% lower risk of stroke, but a government review found the observational evidence inconsistent ^[1]. Kidney stones: potassium citrate reduced new stones in trials, though the effect is attributed to the citrate ^[1].

Too much

In healthy people with normal kidney function, high intakes from food are not a risk ^[1]. But in people whose kidneys excrete potassium poorly — because of chronic kidney disease or medicines such as ACE inhibitors or potassium-sparing diuretics — even intakes below the Adequate Intake can cause hyperkalemia, as can type 1 diabetes, heart failure, adrenal insufficiency or liver disease ^[1]. Severe hyperkalemia can cause muscle weakness, paralysis, palpitations and life-threatening heart rhythms ^[1]. Very large amounts from supplements or salt substitutes can cause it even in healthy people ^[1].

Medicines that interact

ACE inhibitors such as benazepril and angiotensin receptor blockers such as losartan reduce potassium loss in urine and can cause hyperkalemia, as can potassium-sparing diuretics such as amiloride and spironolactone ^[1]. Loop diuretics such as furosemide and thiazides increase potassium loss and can cause hypokalemia ^[1]. Experts recommend monitoring potassium in people taking any of these ^[1]. If you take one regularly, talk to your doctor or pharmacist before taking a potassium supplement or using a salt substitute.