How potassium lowers blood pressure

Potassium lowers blood pressure in people with high blood pressure. In 16 trials in such people, more potassium lowered systolic pressure by 5.3 mmHg and diastolic pressure by 3.1 mmHg. In 3 trials in people without high blood pressure, the change was close to zero and not significant.^[1] The leading explanation is in the kidney. When blood potassium rises, the distal tubules take back less sodium, and more sodium leaves in urine.^[2] In mice, low potassium did the opposite: the kidney kept more sodium.^[3] In people, the step in which more sodium leaves in urine is the least certain: in a 5-day trial, sodium in urine did not rise.^[4]

Why does the kidney keep sodium when potassium is low?

To keep potassium. When blood potassium is low, NCC takes back more sodium. This limits the loss of potassium, even at the cost of higher blood pressure.^[3]

A 2026 review explains why this matters today. The switch suits the diet of hunter-gatherers: little salt, with times of plenty and times of hunger. A modern diet often has much salt and little potassium. Then the switch keeps potassium by taking back more sodium. This can make salt-sensitive high blood pressure worse, that is, blood pressure that rises with salt.^[10]

The path from food to blood pressure has four stops. Potassium enters the blood. The distal tubule senses it and takes back less sodium. Potassium and some extra sodium leave in urine, and the body keeps less fluid.^[2]

Is the sodium step proven in people?

Not fully. A 2020 review by researchers who study the switch says that the kidney plays a major role in how a diet rich in potassium lowers blood pressure.^[2] The parts of the path have support of different strength:

• The NCC switch: shown in mice and cells, where low potassium switched NCC on,^[3] and in people as lower NCC in urine samples after 5 days of extra potassium.^[4]
• More sodium in urine within hours: shown after a single dose of 100 mmol of potassium chloride in 7 healthy people.^[7]
• More sodium in urine over days: seen in 8 young Black volunteers who took 80 mmol of potassium chloride a day for 4 days. The abstract reports this result for them, not for the 6 white volunteers.^[11] In the 5-day trial of 18 adults, sodium in urine did not rise.^[4]
• The opposite direction: 10 healthy men ate 10 mmol of potassium a day for 9 days, against 90 mmol in the other period. Their blood potassium fell from 3.8 to 3.2 mmol/L. They passed much less sodium in urine (10 against 144 mmol a day), and their mean arterial pressure rose from 90.9 to 95.0 mmHg.^[12]

The authors of the 5-day trial note two limits. Urine was collected only from day 5 to day 6, so an early rise in sodium could have been missed. The trial was too small to detect a change in blood pressure, and no change was detected.^[4]

Potassium may also lower blood pressure in other ways. A diet rich in potassium is reported to act on potassium channels and the sodium-potassium pump in the cells of artery walls, and this widens the arteries.^[2] NIH ODS names both routes: wider blood vessels, and more sodium in urine, which lowers the volume of blood plasma.^[6]

How much does potassium lower blood pressure?

In people with high blood pressure, the fall is a few mmHg. A 2013 review pooled 22 trials with 1,606 adults. Overall, more potassium lowered blood pressure by about 3.5/2.0 mmHg. The effect was seen in people with high blood pressure, not in those without it.^[1] A 2026 review of 19 trials in 803 people with untreated high blood pressure found a fall of 5.3/4.5 mmHg in the clinic. Measured with a portable monitor over 24 hours, the fall was smaller: 2.8/3.2 mmHg.^[8]

The fall was larger when people ate more salt.^[13] In the 2013 review, systolic pressure fell by 6.9 mmHg in trials with more than 4 g of sodium a day. With 2 to 4 g of sodium, it fell by 2.0 mmHg. The difference between the two groups was not significant.^[1]

More is not always better. A 2020 analysis pooled 32 trials that lasted at least 4 weeks. Blood pressure was about the same with 90 to 150 mmol of potassium in urine a day. At 60 mmol, systolic pressure was 3.9 mmHg higher than at 90 mmol.^[13] The 2013 review found the largest fall when people reached 90 to 120 mmol a day, but no clear dose effect.^[1] The model applies the 2020 curve to potassium intake, so in the model 3.5 g a day gives about 80% of the systolic fall of 4.7 g. The analysis itself measured potassium in urine and found little difference between 90 and 150 mmol a day.^[13]

Should the extra potassium come from food or supplements?

The World Health Organization (WHO) recommends more potassium from food to lower blood pressure in adults. It suggests at least 90 mmol (3,510 mg) a day.^[14] In the US, the adequate intake is 3,400 mg a day for men and 2,600 mg for women. On average, US men get 3,016 mg a day from food and women 2,320 mg.^[6]

Many fruits and vegetables, some legumes and potatoes are rich in potassium:^[6]

• a medium baked potato, flesh only: 610 mg^[6]
• a cup of canned kidney beans: 607 mg^[6]
• a medium banana: 422 mg^[6]

Most potassium supplements contain at most 99 mg per serving. In the US, people who take them get only 87 mg a day more on average.^[6] The trials in a 2017 review used much more: mostly potassium chloride, 30 to 120 mmol (1,173 to 4,692 mg) a day.^[6]

Salt substitutes replace part of the salt with potassium chloride. In 13 trials, mostly in people with high blood pressure, they lowered blood pressure by 5.58/2.88 mmHg. Part of this effect may come from eating less sodium, not from the potassium.^[6]

Who should be careful with extra potassium?

Too much potassium in the blood is called hyperkalemia: a level above 5.0 mmol/L.^[6] In healthy people with normal kidneys, potassium from food does not cause it, because the kidneys pass the extra into urine.^[6] Very high amounts of potassium supplements or salt substitutes can be more than the kidneys can pass, and can cause sudden hyperkalemia even in healthy people.^[6]

These medicines lower the potassium that the kidneys pass into urine and can cause hyperkalemia:^[6]

• ACE inhibitors, such as benazepril^[6]
• angiotensin receptor blockers (ARBs), such as losartan^[6]
• potassium-sparing diuretics, such as amiloride and spironolactone^[6]

In chronic kidney disease, and with ACE inhibitors or potassium-sparing diuretics, even less potassium than the adequate intake can cause hyperkalemia. It can also occur with type 1 diabetes, heart failure, adrenal insufficiency or liver disease. Severe hyperkalemia can cause muscle weakness, palpitations and heart rhythm problems that can be life-threatening.^[6] Salt substitutes contain 440 to 2,800 mg of potassium per teaspoon, so the same people should ask before they use them.^[6]

In the 2026 review, adverse events were more frequent with potassium supplements: 12.8%, against 3.2% in the comparison groups.^[8] In the 2020 dose analysis, blood pressure rose at high potassium intakes in people who took blood pressure medicines, but not in untreated people.^[13] The WHO advice does not cover people whose kidneys pass less potassium because of a disease or a medicine.^[14]

Ask a doctor or pharmacist first if you have kidney disease, take one of the medicines above or have one of the conditions above. Ask before you take potassium supplements or use a salt substitute.^[6]

In short

• In people with high blood pressure, more potassium lowered it by about 5.3/3.1 mmHg. In people with normal blood pressure, the change was close to zero.^[1]
• When blood potassium rises, the distal tubules take back less sodium through NCC.^[2] In mice, low potassium switched NCC on. In one 5-day trial in 18 adults, extra potassium lowered NCC in urine samples.^[3][4]
• That more sodium then leaves in urine over days is the least certain step in people: the 5-day trial did not find it.^[4]
• Blood pressure was about the same with 90 to 150 mmol of potassium in urine a day.^[13]
• The WHO advises more potassium from food, at least 90 mmol (3,510 mg) a day.^[14] Most supplements contain at most 99 mg.^[6]
• With kidney disease, ACE inhibitors, ARBs or potassium-sparing diuretics, extra potassium can cause hyperkalemia.^[6]

What this figure leaves out

The kidney, its vessels and the ureter come from the Human Reference Atlas, shared under the CC BY 4.0 licence. They are a female left kidney (version 1.3), the female blood vessels (version 1.3) and a female left ureter (version 1.2).^[15][16][17] The dots and the glow are signs, not single molecules.

The numbers come from a small model, not from measurements in one person. Blood potassium rises by 0.4 mmol/L for 72 mmol of extra potassium a day, and NCC falls with it, to 0.74 of usual at that rise, as in the 5-day trial.^[4] So at 4.7 g a day, blood potassium in the model rises from 4.0 to about 4.3 mmol/L and NCC falls to 78% of usual. The blood pressure after 4 weeks comes from the 2013 review,^[1] and the smaller effect at 3.5 g from the 2020 dose curve.^[13]

Three things are modelled and not measured:

• the extra sodium in urine, about 65 mmol in all and most of it in the first week. The 5-day trial found no extra sodium on day 5, so the model keeps it small.^[4]
• the path of blood pressure between day 0 and week 4. The 2026 review pooled blood pressure at the end of the trials.^[8]
• a salt intake of 150 mmol of sodium a day. In trials, the fall in blood pressure was larger with more salt.^[13]

The model leaves out the widening of arteries.^[2] It does not apply to people with kidney disease or who take medicines that keep potassium in the body.^[6] For education; not for diagnosis.