Phosphorus is a mineral found in many foods. It works with calcium and vitamin D to keep your bones healthy. Healthy kidneys help keep the right balance of phosphorus in your body. When you are on dialysis, phosphorus can build up in your blood. Having too much phosphorus is called hyperphosphatemia. This can lead to bone disease, which causes weak bones that break easily. Limiting the amount of phosphorus you take in can help prevent this problem. Talk to your dietitian about how much phosphorus you should have each day.