Potassium

Potassium is the main cation inside cells and an essential electrolyte, supporting nerve transmission, muscle contraction including the heartbeat, and the maintenance of acid-base and fluid balance; its blood level is held within a tight range by the kidneys. Deficiency, or hypokalaemia, causes muscle weakness and lethargy, and in marked feline cases it produces a striking sign: the cat becomes unable to lift its head, letting the chin droop toward the chest, a posture called ventroflexion of the neck. Hypokalaemia is a frequent concern in cats with chronic kidney disease, because the diseased kidneys leak potassium into the urine, which is exactly why many therapeutic renal diets are enriched with potassium to compensate. The opposite problem, too much potassium in the blood, or hyperkalaemia, is dangerous to the heart and arises mainly in urinary obstruction or acute kidney failure, both veterinary emergencies. In a healthy animal eating a complete food, potassium balance is normally maintained without difficulty. Sources include meat, fish and many plant foods. Formulation accounts for the interplay between potassium, [sodium](/glossary/sodium) and chloride, since these electrolytes work together. The renal connection ties potassium to the wider discussion of kidney-friendly diets and the [protein-to-phosphorus ratio](/glossary/protein-to-phosphorus-ratio). See the [Petipedia glossary](/glossary).

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