The Serum Phosphorus test measures the level of phosphorus in the blood, an essential mineral for bone formation, energy storage, and cellular function. Phosphorus levels are regulated by the kidneys and influenced by factors such as diet, kidney function, and hormone levels. Abnormal phosphorus levels may indicate issues related to bone health, kidney disease, or imbalances in calcium and vitamin D, making this test valuable in assessing metabolic and bone-related conditions.