If dialysis does not remove enough phosphorus from your system, it can cause harm to your body. For example, high phosphorus can over stimulate the parathyroid and cause overproduction of the Parathyroid Hormone (PTH) resulting in excessive itching and bone disease.
Fortunately for dialysis patients Phosphorus (Phosphate) Binders can help mitigate against those symptoms. Phosphorus Binders are medicines which are taken shortly before meals or snacks to bind the phosphorus in your stomach to the food that you digest. Thus reducing the amount of phosphorus absorbed in your blood. Therefore, by taking phosphorus binders plus reducing the intake of phosphorus in your diet, you can retain more calcium in your bones, which is the most desirable outcome .
Phosphorus Binders usually contain calcium. These include Calcium Carbonate (TUMS) and Calcium Acetate (PhosLo). Note that excessive calcium can form hardened deposits know as calcification. Depending on their locations, they can cause joint pain or heart and lung disease. That is why you should limit your intake to between 1000 to 1200mg per day. For this reason, phosphate binders also come in forms that do NOT contain calcium such as Sevelamer (Renagel). KidneyBuzz.com suggests that you check with your dietitian in selecting the binder best suited for your condition and remember to take them before every meal or snack in order to receive the maximum benefit in avoiding itching and breakage of bones.
Reference: "Lifestyle Changes on Dialysis." - DaVita.