Phosphate on the NCLEX
Hypophosphatemia and hyperphosphatemia: CKD context, refeeding syndrome.
Phosphate 2.5-4.5. Tested less than other electrolytes but key in CKD and refeeding.
Hypophosphatemia (<2.5)
Causes: refeeding syndrome, alcoholism, DKA insulin treatment, malabsorption. Signs: muscle weakness, respiratory failure, hemolysis. Treatment: oral or IV phosphate replacement.
Hyperphosphatemia (>4.5)
Causes: CKD (most common), tumor lysis, vitamin D toxicity. Signs: associated hypocalcemia. Calcium-phosphate precipitation (vascular calcification, pruritus). Treatment: phosphate binders with meals (calcium acetate, sevelamer, lanthanum). Dietary restriction.
Refeeding syndrome
Severely malnourished patient suddenly fed → insulin surge → K+, Mg, phos drop dramatically. Replace before feeding in high-risk patients. Advance feeds slowly. Monitor closely.
Frequently asked
Phosphate binder timing?
With meals. Binds dietary phosphate before absorption.
Calcium-phos product?
Ca × P. >55 increases vascular calcification risk in CKD.
Quick check
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