Hyperphosphataemia is a higher-than-normal concentration of phosphate in the blood — above about 1.5 mmol/L in adults. The commonest cause is failing kidneys, which can no longer excrete the phosphate absorbed from food; it also follows massive cell breakdown (tumour lysis, rhabdomyolysis), excess vitamin D, and hypoparathyroidism. Chronically elevated phosphate — the scourge of dialysis patients — combines with calcium to calcify blood vessels, skin, and organs, driving cardiovascular death in kidney disease. Management restricts dietary phosphate (dairy, nuts, cola, processed foods with phosphate additives), binds it in the gut with phosphate-binder drugs taken with meals, and dialyses it away. An electrolyte abnormality of the chronically ill.