Serum Creatinine to Estimated Glomerular Filtration Rate (eGFR) Ratio (24-hour urine collection)
This test measures the ratio of your serum creatinine level to your estimated glomerular filtration rate (eGFR), using a 24-hour urine sample. It helps assess how well your kidneys are filtering waste products over time.
This ratio helps identify kidney function trends and potential causes of kidney issues.
Key facts at a glance
- LOINC
- 67873-0
- Short code
- RFP
- Synonyms
- —
- Category
- chemistry
- Sample
- serum
- Container
- Not applicable - this is a reported clinical finding based on integrated laboratory and clinical data
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- reported
- SNOMED
- 271737000
- Specimen volume
- Not applicable - no direct specimen required; reporting field based on other test results
- Stability
- Not applicable - reported clinical finding
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 1–24 hours
- Order
- routine
Why This Test Is Used
Your doctor may order this test if they suspect chronic kidney disease (CKD) or if you have symptoms like swelling, fatigue, or changes in urine output. It helps determine whether kidney function is declining over time by comparing creatinine levels in your blood to how much waste your urine removes in 24 hours.
How the Test Works
A 24-hour urine sample is collected to measure how much creatinine is excreted. Your blood serum creatinine level is also measured. The eGFR is calculated based on your blood test results and urine creatinine output, then compared to determine the ratio.
What to Expect Before the Test
You’ll need to collect all urine for a full 24-hour period (typically from one morning to the next morning). Drink enough fluids to produce urine throughout the day, but avoid excessive amounts. Store the urine sample in a refrigerator until you return it to the lab.
What to Expect During the Test
No special preparation is needed beyond collecting the urine sample. Blood is drawn from a vein (usually in your arm) for the serum creatinine test.
Reference range
Not applicable - this is a reported clinical finding identifying the primary cause of renal failureN/A
No special patient preparation required for this reporting field. Underlying diagnostic tests may have specific preparation requirements.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A high ratio may indicate poor kidney function or reduced urine output, suggesting underlying kidney disease or obstruction. A low ratio could indicate overhydration or other conditions affecting urine concentration. This test helps monitor kidney health and guide treatment decisions for conditions like chronic kidney disease or urinary tract issues.
Short name
None
Frequently asked questions
How often should I expect this test?
Does this test involve fasting?
What if I miss collecting urine for part of the 24-hour period?
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 16, 2026. · Read our editorial policy