Urine Phosphate-to-Creatinine Ratio (Calculated)
A urine test that compares phosphate with creatinine to help assess phosphate excretion and account for how concentrated or dilute the urine is.
["This ratio helps determine how much phosphate is being lost in the urine relative to creatinine."]
Key facts at a glance
- LOINC
- 56964-0
- Short code
- Phosphate/Creat Ur-Rto
- Synonyms
- Phosphate/Creat Ur-Rto
- 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?
The urine phosphate-to-creatinine ratio is a calculated test that compares the amount of phosphate in a urine sample with the amount of creatinine. Creatinine is used as a reference because it is usually released at a relatively steady rate, helping adjust for differences in urine concentration.
Why might I need this test?
Your clinician may use this test when evaluating high or low blood phosphate, kidney stone risk, or conditions that affect how the kidneys and bones handle phosphate. It can also help identify whether too much phosphate is being lost in the urine.
How is the test performed?
A urine sample is tested to measure phosphate and creatinine, and the laboratory calculates their ratio. The order may specify a single urine sample or a timed collection, so follow the collection instructions provided by your healthcare professional.
How do I prepare for the test?
Fasting is generally not required unless your clinician specifically requests it. Continue your normal diet and medications unless instructed otherwise, and be sure to complete any timed urine collection exactly as directed.
Reference range
Adult: 2.5-4.5 mg/dLN/A
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.
A high ratio may indicate that increased amounts of phosphate are being excreted, which can occur with high dietary intake, medications, or conditions that alter phosphate handling. A low ratio may occur with reduced phosphate intake, increased kidney reabsorption, or very dilute urine. Age, kidney function, diet, and the type of urine collection can affect the result, so it should be interpreted alongside your other laboratory tests and medical history.
Short name
Urine phosphate/creatinine ratio
Frequently asked questions
What does the phosphate-to-creatinine ratio measure?
Why might my phosphate-to-creatinine ratio be abnormal?
Do I need to collect all of my urine for 24 hours?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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