Phosphorus is a mineral that is vital to energy use in your body. Fortunately, there is plenty of it around for your body to use—phosphorus is found in almost all foods. Phosphorus is measured in your blood as phosphate.

Like calcium, phosphorus is stored in your bones and teeth. Just a little bit is let out into your bloodstream. When the kidneys fail, phosphate levels usually go up, which can be bad news. (The good news is, medications and diet changes can help.)

Too much phosphate in your blood, hyperphosphatemia, can make you itch all over, and can damage your bones. Too little phosphate, hypophosphatemia, can cause muscle weakness and coma, but this is very rare.

Like magnets, calcium and phosphorus are attracted to each other. In fact, they join together into crystals that form a strong structure for your bones. Phosphate binders lock onto extra phosphorus and remove it safely in your stool. Binders are sometimes antacids, like Tums®, or can be special drugs just for this purpose, like Renagel®, Renvela®, PhosLo®, Fosrenol®, or many others.

Why is this important? The balance of calcium and phosphorus in your body starts to change early in kidney disease. Instead of neatly forming into bone, extra phosphorus and calcium float around in your bloodstream. Having too much phosphorus tells your body to pull calcium out of storage. This can weaken your bones and lead to fractures.

Even worse, if you have too much calcium and phosphorus in your blood, sharp crystals of calcium phosphate can form. These painful crystals damage blood vessels and other tissues. They can lead to loss of a limb—or even death. This very rare condition is called extraskeletal or metastatic calcification. It is hard to treat, although sometimes special hyperbaric oxygen chambers are used.

Taking phosphate binders with food (lots of binders with a big meal, fewer binders with a small meal or snack) can help you keep your bones healthy.

Doing daily home hemodialysis (HD), 2.5 to 3 hours, 5 to 7 days per week, or nocturnal HD (8-hour treatments, 3 to 6 nights per week while you sleep) removes much more phosphorus than standard in-center HD does. In fact, most people who do nocturnal HD can stop taking phosphate binders—and may even have to add phosphate to their dialysate fluid. In the short term, getting more HD also means having a much more normal diet. In the long term, it can mean a better chance of avoiding renal bone disease.