Phosphate binders are used to decrease the absorption of phosphate from food in the digestive tract.
  They are used when there is an abnormally high blood phosphate level (hyperphosphatemia) which can be caused by impaired renal phosphate excretion or increased extracellular fluid phosphate loads.
  Phosphate binders react with phosphate to form an insoluble compound, making it unable to be absorbed from the gastrointestinal tract. When taken regularly with meals, phosphate binders lower the concentration of phosphate in serum.