Potassium

What potassium does in the body

Potassium is a mineral and an electrolyte, meaning it carries a small electrical charge in body fluid. Almost all of it sits inside your cells, while sodium sits mainly outside them. The push and pull between the two drives nerve signals and muscle contraction. Potassium contributes to normal muscle function, to the normal functioning of the nervous system and to the maintenance of normal blood pressure. In the UK, adults aged 19 to 64 need 3,500 mg a day, and food does most of that work: a jacket potato with the skin, beans, spinach and dried apricots all add up. You will find it next to our other essential minerals.

Why the doses on the label look small

Most potassium capsules and tablets supply around 99 mg of elemental potassium, roughly 3% of the UK daily figure. That is deliberate, not stinginess. Potassium is cleared by the kidneys, so food supplements keep single doses low. Treat a potassium capsule as a small top-up beside food, never as a replacement for vegetables and pulses. Powders work differently: they mix sodium, potassium and magnesium in amounts built for sweat losses, which is why heavy sweaters often do better with electrolyte drinks and powders.

Forms differ in feel, not in magic

Potassium is always bound to another substance: chloride, citrate, gluconate, bicarbonate or aspartate. The label should state the elemental potassium, the part your body counts, not the weight of the whole salt. Citrate and bicarbonate are alkaline salts and sit comfortably with most people. Chloride is the form in salt substitutes and sports blends, and it is the one most often called harsh on an empty stomach. Gluconate is mild but bulky, so capsule counts run higher.

How we pick potassium products

We judge three things: the form, the elemental dose printed on the label, and whether the combination makes sense. For daily use we lean towards citrate and bicarbonate, because they are gentle and clearly declared. Chloride we mostly stock inside electrolyte blends, where it belongs. We pass on products that shout the salt weight in large type and bury the elemental amount in small print. Every item clears our compliance team before it goes live, we test products ourselves, and independent labs spot-check batches. Read how we select brands and products.

Who it suits and who should ask first

A potassium top-up makes most sense if your diet is light on vegetables, pulses and potatoes, if you follow a low-carb or keto plan, or if you train hard and sweat a lot. Many people take it beside a magnesium product, since both minerals leave the body in sweat.

Be realistic about scale. A 99 mg capsule is a nudge, not a correction for a diagnosed deficiency, and that is what the dose is designed for. UK guidance says taking 3,700 mg or less a day from supplements is unlikely to cause harm, while higher amounts can cause stomach pain, nausea and diarrhoea. Older people should not take potassium supplements unless a doctor advises it. The same caution applies if you have kidney problems or take blood pressure medicines such as ACE inhibitors or potassium-sparing diuretics: speak to your GP or pharmacist before you start.