Phosphate (urine)


Alternative names, keywords

Urine phosphate output, fractional excretion of phosphate

Samples required

24h urine collection - click here for printable instructions

24 hour urine collection in acidified container.

Urine and serum creatinine and serum phosphate recommended for interpretation.

For fractional excretion of phosphate send

plain random urine and
5 mL clotted blood

Test indications


Test information

Fractional excretion of phosphate (FEPO4):

FEPO4= (urine PO4 x serum creatinine x100)/(serum PO4 x urine creatinine)
(calculation needs serum and urine creatinine in same units)

Factors affecting test performance/ results

No specific interferences noted.

Results should always be assessed in conjunction with the patient’s medical history, clinical examination and other findings.

Reference range

13 - 42 mmol/24h
Source: Roche Cobas® Phosphate kit insert 07-2015, V7.0

Fractional excretion of phosphate:

> 20% implies renal loss (may be due to hormonal as well as renal causes)
≤ 20% implies renal conservation e.g. decreased intake.


Turnaround time

Same day


Biochemistry (Automation)