Serum/Plasma Creatinine-to-Blood Urea Nitrogen Ratio (mratspine)
This test measures the ratio of creatinine (a waste product from muscle metabolism) to blood urea nitrogen (BUN, a measure of kidney function) in your blood. It helps assess kidney health and function.
["This ratio can indicate how well your kidneys are filtering blood and processing waste products."]
Key facts at a glance
- LOINC
- 49565-5
- Short code
- MRA T-spine ves
- Synonyms
- MRA T-spine ves
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- mr-angio
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What Does This Test Measure?
Creatinine is a byproduct of muscle metabolism that the kidneys filter out of the blood. Blood urea nitrogen (BUN) reflects the amount of urea nitrogen in your blood, which comes from protein breakdown. Together, these measures help evaluate kidney function. The ratio can also provide insight into hydration status, blood flow to the kidneys, and potential blockages in the urinary tract.
Why Might Your Doctor Order This Test?
Your doctor may order this test to check for kidney problems, such as chronic kidney disease, acute kidney injury, or conditions affecting blood flow to the kidneys. It can also help diagnose or monitor conditions like heart failure, dehydration, or urinary tract obstructions.
How Is This Test Performed?
A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it is analyzed to determine the levels of creatinine and BUN. The ratio is then calculated based on these values.
What Are Common Causes of Abnormal Results?
High ratios may suggest kidney problems, dehydration, heart failure, or conditions that restrict blood flow to the kidneys. Low ratios could indicate overhydration, liver disease, or certain medications that affect kidney function. Always discuss any changes with your healthcare provider.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A high creatinine-to-BUN ratio can signal impaired kidney function, particularly if creatinine levels are normal. This may indicate conditions like prerenal azotemia (low blood flow to kidneys) or urinary tract obstructions. Conversely, a low ratio might suggest overhydration or liver disease, which can also affect kidney function indirectly. Regular monitoring of this ratio can help track kidney health over time, especially in patients with chronic conditions like diabetes or hypertension.
Short name
Creatinine-to-BUN Ratio
Frequently asked questions
What does a high or low ratio mean?
Can diet or medications affect this test?
How often should this test be repeated?
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