How to evaluate the cause of hypophosphatemia?
Generally, the cause of the hypophosphatemia can be elucidated from the patient’s history, focusing on diet, nutritional status, social habits, and medication use. In situations where it is not clear, a 24-hour urinary phosphate or calculating the TRphos can distinguish renal wasting from GI loss or cellular redistribution. A 24-hour urinary phosphate excretion <100 mg or TRphos >95% is indicative of appropriate renal phosphate retention in the setting of hypophosphatemia.