Stages and labs
Kidney Function Tests: eGFR, Creatinine and ACR Explained
This article is general information. Your nephrologist or renal dietitian knows your lab results and can tell you what is right for you.
Because early kidney disease usually has no symptoms, testing is the only way to find out how well the kidneys are working. NIDDK explains that two tests do most of the work: a blood test and a urine test. This article describes them in general terms and cannot interpret your own results.
Who should be tested
NIDDK says people with diabetes should be checked every year. People with high blood pressure, heart disease or a family history of kidney failure should ask their health care provider how often to be tested. MedlinePlus also lists being over 60, smoking and obesity among the higher-risk groups.
Blood test: creatinine and eGFR
Creatinine is a waste product from normal muscle breakdown. Kidneys remove it from the blood, so the level rises as kidney disease worsens. The estimated glomerular filtration rate (eGFR) is calculated from the creatinine result. MedlinePlus says the test is a standard blood draw from a vein in the arm that usually takes under five minutes, and that you may be asked to avoid certain foods, such as meat, for several hours beforehand. Always follow the instructions you are given, and do not stop any medicine unless told to.
NIDDK gives these thresholds for GFR: 60 or more is the normal range, below 60 may indicate kidney disease, and 15 or less is called kidney failure. A full explanation is in What Is eGFR?
Urine test: albumin and the ACR
Albumin is a protein in the blood that passes into the urine when the kidneys are damaged. NIDDK describes two ways to test for it:
- Dipstick test: a chemically treated strip changes color if albumin is present.
- Urine albumin-to-creatinine ratio (UACR, also written ACR or uACR): compares the albumin in a urine sample with its creatinine. NIDDK says a result of 30 mg/g or less is normal, and more than 30 mg/g may indicate kidney disease.
An NIDDK reference sheet for health professionals states that a spot urine sample is enough, that 24-hour collections are not necessary, and that, because the result is a ratio, it is not affected by how concentrated the urine is. NIDDK adds that the provider may repeat the test one or two more times to confirm a result.
Tests that may follow
MedlinePlus says a low eGFR may lead to further tests, such as a urine protein test, a microalbumin creatinine ratio, a BUN test, or a kidney ultrasound or CT scan. The same two tests, eGFR and urine albumin, are used to monitor known kidney disease. According to NIDDK, treatment may be working if the eGFR stays the same and urine albumin stays the same or goes down.
When results are explained
A single result does not tell the whole story. Age, body size, muscle mass, diet and other conditions can all influence the numbers. Your doctor or nephrologist can put your results in context. Our list of questions to ask your nephrologist includes questions about your tests, and CKD Stages 1 to 5 Explained shows how eGFR relates to the stages.
Related reading
Sources
- NIDDK: Tests and Diagnosis of Chronic Kidney Disease
- NIDDK: Urine Albumin-to-Creatinine Ratio (UACR) quick reference sheet for health professionals
- MedlinePlus: eGFR and GFR Tests, updated September 30, 2026
- National Kidney Foundation: Estimated Glomerular Filtration Rate (eGFR), updated February 5, 2026
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