Fractional excretion of phosphate (FEPO4)
Fractional excretion of phosphate: FEPO4 = (urine PO4 x plasma Cr) / (plasma PO4 x urine Cr) x 100; above ~5% in hypophosphatemia indicates renal phosphate wasting.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Urine phosphate
- 30 mg/dL
- Plasma phosphate
- 1.5 mg/dL
- Urine creatinine
- 60 mg/dL
- Plasma creatinine
- 1.0 mg/dL
Result: FEPO4 33.3%: above ~5%, consistent with renal phosphate wasting in hypophosphatemia.
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What the result means
- Reading
- in hypophosphatemia, above ~5% suggests renal phosphate wasting; at or below ~5% points to an extra-renal or redistributive cause.
What you enter
- Urine phosphate
- Plasma phosphate
- Urine creatinine
- Plasma creatinine
How this is calculated
- Formula
- FEPO4 (%) = (urine PO4 x plasma Cr) / (plasma PO4 x urine Cr) x 100; same fractional-excretion structure as FENa.
Walton RJ, Bijvoet OL. Nomogram for derivation of renal threshold phosphate concentration. Lancet. 1975;2(7929):309-310. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.