What It Does
Works hand-in-hand with calcium for bone and dental health, and plays a vital role in energy metabolism, cell repair, and DNA synthesis. But phosphorus has a critical dark side: excess accelerates kidney disease, the leading cause of death in older cats.
What You’ll Notice
In healthy pets, you won't see phosphorus effects directly — it works silently. But in cats and dogs with kidney disease, high phosphorus causes soft tissue calcification, bone resorption, and cardiovascular damage. Vets recommend phosphorus levels of 0.3-0.6% for cats with CKD.
Strong bones
Cell energy
Kidney damage (excess)
Bone loss (excess)
Sources & Notes
Cats over 7 years and any pet with kidney disease. The ideal Ca:P ratio is 1.2:1 to 1.4:1. High-phosphorus diets (especially highly bioavailable forms) may cause kidney damage even in healthy adult cats.