The Phosphorus, Inorganic – Serum test helps to evaluate the phosphorus levels in the blood. It also helps to diagnose those conditions that cause abnormally high or low levels of phosphorus. The Phosphorus, Inorganic – Serum test is done: • In case of abnormal levels of calcium • In case of kidney disorders • In case of uncontrolled diabetes • To monitor the levels when one is taking calcium or phosphate supplements