Kidney Guides
Creatinine, BUN, urine protein, and kidney function testing.
What these guides cover
Kidney guides cover creatinine, BUN, eGFR, and urine protein tests used to assess kidney function. They explain how these markers are combined into an estimated filtration rate and what changes may indicate over time.
Kidney function is usually assessed with a small group of markers rather than a single value. Creatinine is a waste product that the kidneys filter, and BUN is another. An eGFR is calculated from creatinine plus factors such as age and sex to estimate filtration. A urine protein test, often reported as an albumin-to-creatinine ratio, checks whether protein is passing into the urine. Together these markers describe how the kidneys are working over time.
How to use these guides
Each guide below focuses on a single test or a small group of related tests. Start with the marker you and your clinician have discussed, then follow the related-test links to see what is often ordered alongside it. Preparation and timing instructions appear in each guide, and where testing is available is listed by state and city. These guides are educational and do not replace advice from a healthcare provider.
Creatinine Blood Test: What High Levels Really Mean
Learn what a creatinine blood test measures, what high or low levels can mean, and how to order creatinine testing at a CLIA-certified lab n
Kidney Disease Screening: Tests and Who Needs Them
Learn which tests screen for kidney disease, who may benefit from screening, how blood and urine markers work, and how to order testing near
Kidney Function Blood Tests: eGFR and Creatinine Levels
Learn which blood tests check kidney function, how eGFR and creatinine are used, and how to order kidney function testing at a lab near you.
Kidney FAQ
What is eGFR?
eGFR, or estimated glomerular filtration rate, is a calculation based on creatinine and factors such as age and sex. It estimates how well the kidneys are filtering and is read alongside other markers.
Why is a urine protein test included with kidney blood tests?
Blood markers show filtration, while a urine protein test shows whether protein is passing into the urine. Combining the two gives a fuller view of kidney function than either test alone.
Do kidney tests require fasting?
Most kidney function tests need no fasting, though a clinician may ask you to avoid certain foods or to hydrate normally before collection. Check the preparation notes for your specific order.
Reviewed by the LabDirectories Editorial Team
Our team researches and fact-checks all content to ensure accuracy. We update guides regularly to reflect current testing options, pricing, and laboratory accreditation standards.