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Phosphate/Creatinine Ratio, 24-Hour Urine

Published: August 9, 2026Updated: August 17, 2026

Measures the amount of phosphate relative to creatinine in urine collected for 24 hours, helping assess how the kidneys handle phosphate.

Quick summary

["This urine test helps determine whether the kidneys are appropriately reabsorbing phosphate."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
25127-2
Short code
Phosphate/Creat 24h Ur-sRto
Synonyms
Phosphate/Creat 24h Ur-sRto
Category
kidney
Sample
urine
Container
Sterile urine container
Units
N/A
Ref low
2.5
Ref high
4.5
Critical range
1 N/A – —
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84100
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What is this test?

This test measures phosphate and creatinine in a 24-hour urine collection. The phosphate-to-creatinine ratio helps show how much phosphate is being lost in the urine relative to the amount excreted by the kidneys.

Why might I need this test?

It may be ordered to evaluate phosphate balance or investigate unusual phosphate levels, bone symptoms, or possible kidney tubule problems. It is also sometimes used to monitor treatment for conditions that affect phosphate absorption or kidney function.

How is the test performed?

You collect all urine produced during a full 24-hour period in a labeled container provided by the laboratory. The laboratory measures phosphate and creatinine and calculates their ratio.

How do I prepare for the test?

Follow the laboratory's collection instructions, including the exact start and end times, and record any urine that is missed. Keep the container refrigerated if instructed, and do not change your diet, supplements, or medicines unless your clinician tells you to.

Reference range

Adult: 2.5-4.5 mg/dLN/A

Specimen: urine

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

24-Hour Urine Phosphate/Creatinine Ratio

Frequently asked questions

Do I need to fast for this test?
Fasting is usually not required, but follow any specific instructions from the laboratory. Maintaining your usual diet during the collection period helps make the results easier to interpret.
What happens if I miss part of the 24-hour urine collection?
A missed collection can make the result inaccurate and may require repeating the test. Contact the laboratory for instructions if this occurs.
Does this test diagnose a specific condition by itself?
No. The result is one part of evaluating phosphate balance and kidney function and is usually interpreted alongside blood tests, symptoms, and medical history.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy