Potassium Supplements: Forms and How to Choose the Right One
Potassium is one of the minerals most people under-consume, and active people lose some through sweat. Supplements come in several chemical forms, each with its own advantages. Our editorial team explains how they differ, why food usually comes first and who should never take potassium without medical advice.
The role of potassium in the body
Potassium is the main positively charged ion inside cells. Together with sodium, which dominates outside cells, it creates the electrical gradient that allows nerves to fire and muscles, including the heart, to contract. Even small changes in blood potassium can affect heart rhythm, which is why the body regulates it so tightly.
Potassium also helps counteract the effect of sodium on blood pressure. A systematic review commissioned by the World Health Organization (Aburto et al., 2013) found that increasing potassium intake lowered blood pressure in people with hypertension and was associated with a lower risk of stroke.
The UK reference nutrient intake for adults is 3,500 mg per day. National Diet and Nutrition Survey data have consistently shown that many adults, particularly younger women, fall short of this figure. The European Food Safety Authority set an adequate intake of the same 3,500 mg for adults in 2016.
For athletes, potassium losses through sweat are smaller than sodium losses, but they still add up during long sessions in the heat. Low potassium can contribute to muscle weakness and fatigue, although cramps are more often linked to fatigue and neuromuscular factors than to a single mineral.
Food first: the best sources
The most effective way to raise potassium intake is through food. Fruit, vegetables, pulses, potatoes, dairy and nuts are rich sources, and they bring fibre, magnesium and other nutrients that supplements cannot replicate.
| Food | Portion | Approximate potassium |
|---|---|---|
| Baked potato with skin | 1 medium (about 200 g) | Around 1,000 mg |
| Banana | 1 medium | About 400 mg |
| Cooked lentils | 150 g | About 500 mg |
| Spinach, cooked | 100 g | About 450 mg |
| Natural yoghurt | 150 g | About 300 mg |
| Dried apricots | 30 g | About 350 mg |
Food tables vary between sources and cooking methods, so these figures should be seen as rough guides. Boiling vegetables, for example, leaches potassium into the cooking water.
A diet built around the NHS Eatwell Guide, with at least five portions of fruit and vegetables a day, usually brings potassium intake much closer to the target without the risks associated with concentrated supplements.
Supplement forms compared
Potassium supplements always contain potassium combined with another molecule, known as an anion. The choice of anion affects how the product tastes, how it is tolerated in the stomach and what extra effects it may have on the body's acid–base balance.
- Potassium citrate: well absorbed and alkalising. It is used medically to prevent certain types of kidney stones because citrate in urine inhibits stone formation.
- Potassium chloride: the form used to correct low potassium in hospital and in many salt substitutes. It is preferred when chloride is also low, for example after vomiting or with some diuretics.
- Potassium gluconate: gentle on the stomach but provides relatively little potassium per gram, so tablets are large.
- Potassium bicarbonate: alkalising, sometimes studied for bone and muscle preservation in older adults and found in effervescent preparations.
- Potassium in multivitamins: usually present in small amounts that contribute little to daily intake.
In the UK and EU, potassium food supplements typically provide modest amounts per tablet, well below the levels in prescription potassium products. Higher-dose preparations are medicines and should be used only on medical advice.
When reading labels, look for the amount of elemental potassium rather than the weight of the compound. A tablet containing 500 mg of potassium gluconate provides less than 100 mg of actual potassium.
How to choose
For most healthy people, the best "form" is food. A supplement makes sense in specific situations: diagnosed low potassium, very high sweat losses that diet cannot cover, or a medical indication such as stone prevention, which should be guided by a doctor.
If you are prone to calcium oxalate or uric acid stones, potassium citrate is the form most commonly prescribed. If you are taking a diuretic that lowers both potassium and chloride, potassium chloride is usually preferred by clinicians.
Older adults interested in bone health may come across studies of potassium bicarbonate, such as the trial by Sebastian and colleagues (1994), which showed improved calcium balance. These were controlled research settings, and results do not justify self-supplementation without advice.
For athletes, electrolyte drinks or tablets usually contain some potassium together with sodium. During long endurance events, sodium replacement is typically more important, and a balanced electrolyte product is more appropriate than a potassium-only supplement.
Safety and who must avoid supplements
The kidneys normally excrete excess potassium efficiently. When they cannot, potassium accumulates and causes hyperkalaemia, which can lead to dangerous heart rhythm disturbances and even cardiac arrest. This is why supplements are not suitable for everyone.
People with chronic kidney disease, type 1 diabetes with complications or adrenal insufficiency are at higher risk. So are those taking medicines that raise potassium: ACE inhibitors such as ramipril, angiotensin receptor blockers such as losartan, potassium-sparing diuretics such as spironolactone, and some anti-inflammatory drugs.
Potassium-based salt substitutes deserve special mention. A large trial in China (Neal et al., 2021) showed that replacing ordinary salt with a potassium-enriched substitute reduced stroke and death, but participants with serious kidney disease were excluded. Anyone with kidney problems or on the medicines above should check with their GP before using them.
Concentrated potassium tablets can also irritate the oesophagus and stomach, so they should be swallowed with plenty of water and food. Slow-release forms were developed partly for this reason.
Editorial conclusions
Potassium is crucial for nerve and muscle function and blood pressure control, and many UK adults do not reach the target of 3,500 mg per day.
Food is the safest and most effective source, while supplements vary by form: citrate for stone prevention, chloride for correcting deficiency with low chloride, and gluconate or bicarbonate for specific uses.
People with kidney disease or those taking blood pressure medicines that raise potassium should never supplement without medical advice.
Our editorial team also suggests articles on electrolytes for endurance athletes, magnesium forms and their differences, and how salt intake affects blood pressure.
References
- Aburto NJ, Hanson S, Gutierrez H, et al. Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ. 2013;346:f1378.
- Neal B, Wu Y, Feng X, et al. Effect of salt substitution on cardiovascular events and death. N Engl J Med. 2021;385(12):1067–1077.
- Weaver CM. Potassium and health. Adv Nutr. 2013;4(3):368S–377S.
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Dietary reference values for potassium. EFSA J. 2016;14(10):4592.
- Sebastian A, Harris ST, Ottaway JH, Todd KM, Morris RC Jr. Improved mineral balance and skeletal metabolism in postmenopausal women treated with potassium bicarbonate. N Engl J Med. 1994;330(25):1776–1781.
- Department of Health. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Report on Health and Social Subjects 41. London: HMSO; 1991.
