For most people, the best form of potassium is food. Fruits, vegetables, beans, dairy and fish supply hundreds of milligrams per serving, while over-the-counter supplements usually contain no more than 99 mg. Among supplement forms, potassium chloride, citrate and gluconate are all used, and the little research there is suggests the body absorbs them well. No form has been shown to be better for the heart than the others.
Key Takeaways
- Potassium is needed for normal heart function, muscle contraction and nerve signaling, because it maintains the electrical gradient across every cell membrane.
- The Adequate Intake is 3,400 mg a day for adult men and 2,600 mg for adult women. Average US intakes fall short, especially among women.
- Supplements often contain potassium chloride, citrate, gluconate, bicarbonate, phosphate or aspartate. One trial found potassium gluconate was absorbed about as well as potassium from potatoes.
- Most over-the-counter potassium supplements stop at 99 mg, about 2% of the Daily Value, because of FDA rules on potassium drug products. A banana has about 422 mg.
- There is no upper limit for healthy people with normal kidney function, but potassium can build up in the blood when the kidneys cannot clear it.
- Talk to your doctor before using potassium supplements or salt substitutes if you have reduced kidney function or take prescription medicines.
Evidence grade: Moderate. Potassium's role in heart and muscle function and its intake targets are established NIH reference values, but human research comparing supplement forms is limited to a few small absorption studies.
What Potassium Does for Your Heart and Muscles
Potassium is the most abundant positively charged mineral inside your cells. The concentration of potassium inside cells is about 30 times higher than outside them. A pump in the cell membrane, the sodium-potassium ATPase, keeps it that way. That difference creates an electrical gradient, and the NIH Office of Dietary Supplements explains that this gradient is required for proper nerve transmission, muscle contraction and kidney function.
The heart is a muscle that contracts and resets with every beat, so it depends on that gradient too. The NIH consumer fact sheet lists heart function, muscle contraction and nerve transmission among the things your body needs potassium for. Balance is what matters. MedlinePlus notes that both low and high blood potassium can cause abnormal heart rhythms. A normal blood level is about 3.6 to 5.0 mmol/L, and healthy kidneys keep it in that range by adjusting how much potassium leaves in the urine.
For a broader look at what the mineral does, see our guide to potassium benefits.
Forms of Potassium Compared
The form of potassium is the compound it is paired with. Supplement Facts panels list elemental potassium, not the weight of the whole compound, so 99 mg of potassium is 99 mg whichever form it comes in.
| Form | Where you find it | What research shows |
|---|---|---|
| Food potassium (phosphate, sulfate, citrate and other forms) | Fruits, vegetables, beans, dairy, meat and fish | About 85–90% of dietary potassium is absorbed. Fruits and vegetables do not contain potassium chloride. |
| Potassium chloride | The most common supplement form; salt substitutes; many electrolyte mixes | Liquid forms used as drugs are absorbed within a few hours; enteric-coated tablets are absorbed more slowly. |
| Potassium citrate | Supplements | Listed by ODS as a common supplement form. ODS notes that only a few studies have examined how well the different supplement forms are absorbed. |
| Potassium gluconate | Supplements | A 2016 randomized trial found about 94% absorption, similar to potassium from potatoes. |
| Potassium bicarbonate, phosphate, aspartate | Supplements | Also used in supplements; little direct comparison data. |
| Potassium iodide | Some multivitamins, in microgram amounts | Supplies iodine, not a meaningful amount of potassium. |
What the absorption trial found
In the 2016 crossover trial, 35 healthy adults ate a controlled diet and added 20, 40 or 60 milliequivalents of potassium a day from either potassium gluconate or unfried potatoes. Blood potassium rose with the dose and did not differ by source. Absorption was high, above 94%, in every arm. The study ran in 5-day phases and found no difference in blood pressure between sources or doses over that short period.
So which form is best?
The honest answer is that the form matters less than the amount and the source. A supplement capped at 99 mg adds very little to the 2,600 to 3,400 mg most adults need. Survey data show the same thing: among the 12% of Americans who take a potassium-containing supplement, it adds a mean of only 87 mg a day. Food is where nearly all potassium comes from.
Potassium also shows up in electrolyte drink mixes. OPA's ION+ Select Electrolyte Powder, for example, supplies potassium as potassium chloride along with magnesium, sodium from pink salt and vitamin B12, and is designed for hydration during fasting windows, workouts and active days. Products like this support hydration routines. They are not a replacement for potassium-rich food.
Why Potassium Supplements Stop at 99 mg
Many supplement makers cap potassium at 99 mg per serving, which is only about 2% of the 4,700 mg Daily Value. ODS gives two reasons, both tied to potassium drug products. First, FDA ruled that some oral drug products with potassium chloride above 99 mg are not safe, because they were linked to small-bowel lesions. Second, FDA requires certain potassium salt drugs with more than 99 mg per tablet to carry a warning about those lesions. The federal rule describes the reported lesions as causing obstruction, bleeding and perforation in some cases.
FDA has not ruled on whether dietary supplements above 99 mg must carry the warning. Most brands have stayed at 99 mg anyway. Under the same federal rule, coated potassium tablets that supply 100 mg or more must carry the prescription-only caution statement.
Best Food Sources of Potassium
Fruits and vegetables are the richest sources, along with legumes, potatoes, dairy, fish and meat. Whole-wheat flour and brown rice contain much more potassium than white flour and white rice. The amounts below come from the NIH Office of Dietary Supplements, based on USDA FoodData Central.
| Food | Serving | Potassium (mg) | % DV |
|---|---|---|---|
| Apricots, dried | ½ cup | 755 | 16 |
| Lentils, cooked | 1 cup | 731 | 16 |
| Prunes, dried | ½ cup | 635 | 14 |
| Potato, baked, flesh only | 1 medium | 610 | 13 |
| Kidney beans, canned | 1 cup | 607 | 13 |
| Orange juice | 1 cup | 496 | 11 |
| Banana | 1 medium | 422 | 9 |
| Milk, 1% | 1 cup | 366 | 8 |
| Spinach, raw | 2 cups | 334 | 7 |
| Chicken breast, grilled | 3 ounces | 332 | 7 |
| Salmon, Atlantic, farmed, cooked | 3 ounces | 326 | 7 |
| Typical potassium-only supplement | 1 serving | up to 99 | 2 |
A single baked potato or cup of lentils supplies more than six capsules' worth of a typical potassium supplement. For more ideas, see our heart-healthy foods list.
How Much Potassium Do You Need?
In 2019, a National Academies committee updated the potassium values. It found too little data to set an average requirement, so it set Adequate Intakes (AIs) based on the highest median intakes in healthy people. It also found the evidence insufficient to set a separate intake level aimed at reducing chronic disease risk.
| Age | Male | Female | Pregnancy | Lactation |
|---|---|---|---|---|
| 1–3 years | 2,000 mg | 2,000 mg | ||
| 4–8 years | 2,300 mg | 2,300 mg | ||
| 9–13 years | 2,500 mg | 2,300 mg | ||
| 14–18 years | 3,000 mg | 2,300 mg | 2,600 mg | 2,500 mg |
| 19+ years | 3,400 mg | 2,600 mg | 2,900 mg | 2,800 mg |
These AIs do not apply to people whose kidneys or medications limit how much potassium they can excrete. The 4,700 mg figure you see on Nutrition Facts labels is the Daily Value, a labeling reference, not a personal target. On average, US men aged 20 and older get 3,016 mg a day from food and women get 2,320 mg, which is why the Dietary Guidelines for Americans has called potassium a nutrient of public health concern.
Signs Potassium Is Too Low or Too High
Too low
Low blood potassium (below about 3.6 mmol/L) is rare in healthy people with normal kidney function, and it is rarely caused by diet alone. It usually follows vomiting, diarrhea, heavy sweating, laxative overuse or certain diuretics. Mild cases can cause constipation, fatigue, muscle weakness and malaise. More severe cases can affect muscle strength and heart rhythm. Low magnesium can make potassium harder to hold onto, because it increases potassium losses in urine. Our guide to magnesium-rich foods can help. Athletes who sweat heavily can find more in our article on electrolyte management during long-distance races.
Too high
High blood potassium (above 5.0 mmol/L) often causes no symptoms. When it does, MedlinePlus lists palpitations, a slow, weak or irregular pulse, chest pain, nausea and trouble breathing. ODS adds muscle weakness and tingling, and notes that severe cases can cause dangerous heart rhythms. Chest pain, trouble breathing or an irregular heartbeat need prompt medical care.
Safety and Interactions
- No upper limit for healthy people. The National Academies did not set a Tolerable Upper Intake Level, because high potassium intake from food does not cause problems when the kidneys work normally. Very high doses of supplements or salt substitutes can still exceed what the kidneys can clear, even in healthy people.
- Kidney function. In people with chronic kidney disease, even intakes below the AI can raise blood potassium. Anyone with reduced kidney function should ask a doctor or registered dietitian about potassium from all sources, including salt substitutes.
- Salt substitutes. Many replace sodium chloride with potassium chloride and provide about 440 to 2,800 mg of potassium per teaspoon, far more than any over-the-counter supplement.
- Digestive effects. Potassium supplements can cause minor digestive side effects. Some potassium salt drug products have been linked to small-bowel lesions.
- Other conditions. ODS notes that high blood potassium can also occur with type 1 diabetes, congestive heart failure, adrenal insufficiency or liver disease. Ask your clinician before supplementing if any of these apply.
- Medications that raise potassium. Talk to your doctor or pharmacist before using potassium supplements or salt substitutes if you take an ACE inhibitor (such as benazepril), an angiotensin receptor blocker or ARB (such as losartan), or a potassium-sparing diuretic (such as spironolactone, amiloride or triamterene). These medicines reduce how much potassium leaves in the urine.
- Medications that lower potassium. Loop diuretics (such as furosemide) and thiazide diuretics (such as chlorothiazide) increase potassium losses. Your prescriber may monitor your levels. Do not add potassium on your own.
Frequently Asked Questions
What is the best form of potassium for the heart?
Potassium from food is the best-supported choice, since it supplies far more potassium than over-the-counter supplements. Among supplements, no form has been shown to be better for heart function. Potassium gluconate was absorbed as well as potassium from potatoes in one trial, and chloride and citrate are also common.
Does potassium help the heart relax between beats?
Potassium is needed for the heart's normal electrical activity. The difference in potassium inside and outside cells is what allows muscle cells, including heart muscle, to contract and reset. Too little or too much potassium in the blood can disturb heart rhythm, so normal levels, not the highest possible levels, are the goal.
How does high potassium affect the heart?
When blood potassium rises above the normal range, it can interfere with the heart's electrical signals. It may cause palpitations, a slow or irregular pulse, muscle weakness or, in severe cases, dangerous rhythm changes. It is most likely when the kidneys cannot clear potassium or certain medicines reduce its excretion.
Why do potassium supplements only have 99 mg?
FDA rules on potassium drug products link some potassium salts above 99 mg per tablet to small-bowel lesions and require a warning on certain products. Most supplement makers stay at or below 99 mg as a result, which is about 2% of the Daily Value.
How much potassium should I get each day?
The Adequate Intake is 3,400 mg a day for men and 2,600 mg for women aged 19 and older, with 2,900 mg in pregnancy and 2,800 mg while breastfeeding. The 4,700 mg figure on food labels is the Daily Value used for labeling. Ask your clinician for a personal target if you have kidney concerns or take prescription medicines.
Sources
- NIH Office of Dietary Supplements. Potassium: Fact Sheet for Health Professionals.
- NIH Office of Dietary Supplements. Potassium: Fact Sheet for Consumers.
- MedlinePlus Medical Encyclopedia. Potassium in diet. National Library of Medicine.
- MedlinePlus Medical Encyclopedia. High potassium level. National Library of Medicine.
- Macdonald-Clarke CJ, Martin BR, McCabe LD, et al. Bioavailability of potassium from potatoes and potassium gluconate: a randomized dose response trial. Am J Clin Nutr. 2016.
- U.S. Food and Drug Administration. 21 CFR 201.306: Potassium salt preparations intended for oral ingestion by man. Electronic Code of Federal Regulations.
- U.S. Department of Agriculture, Agricultural Research Service. FoodData Central.
Disclosure: OPA Nutrition sells supplements, including products mentioned in this article. This content is for education only and is not medical advice. Statements about dietary supplements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. Talk to your healthcare provider before using any supplement, especially if you take medication or have a medical condition.
Written and reviewed by Michael Gonzales, Founder, OPA Nutrition · Last reviewed: · How OPA researches and writes
