BUN/
BUN, creatinine, eGFR, and their ratio, from one blood draw.
- 2,000+ lab locations. Find one near you
- Nothing due at the lab. FSA / HSA accepted
- Ordered by a licensed clinician
At a glance
- Collection
- Blood drawA standard blood draw at the lab.
- Preparation
- NoneNothing to do ahead of time. Water is fine.
- Results
- 1 to 2 daysTypical turnaround after your visit.
- Where
- 2,000+ lab locationsNationwide, with nothing due at the lab.
About this test
This test measures BUN and creatinine, two waste products your kidneys clear, and reports your estimated filtration rate (eGFR) and the ratio between BUN and creatinine. The ratio adds context, such as whether a change may relate to hydration or blood flow. No fasting is needed.
For adults 18 and older. Test availability varies by lab location.
Who should take this test?
This test is for adults whose healthcare provider wants kidney markers with added context, often to follow a past BUN or creatinine result or during medication check-ins.
Ask about this test
Not sure this is the right test?
AI-generated. For information only, not medical advice. Call 911 for an emergency.
What does this test measure?
Your results show your BUN, creatinine, eGFR, and the ratio between them, which can help a healthcare provider read kidney function together with hydration and blood flow.
- Blood urea nitrogen (BUN)
- Urea is a waste product your liver makes when it breaks down protein, and your kidneys clear it into urine. BUN measures the urea nitrogen in your blood. It can shift with hydration, the protein in your diet, and how well the kidneys are filtering, so it is read with creatinine.
- Why it’s measured: To help gauge kidney filtering and hydration, read alongside creatinine.
- Creatinine
- Creatinine is a waste product made at a fairly steady rate by your muscles and removed by your kidneys. Because the kidneys clear it, the level in your blood helps show how well they are filtering. Muscle mass, age, and sex affect the usual level, so it is read in context.
- Why it’s measured: A common measure of kidney filtering, and the basis for eGFR.
- Estimated glomerular filtration rate (eGFR)
- eGFR is not measured directly. The lab calculates it from your creatinine result along with your age and sex to estimate how much blood your kidneys filter each minute. It gives a clearer view of kidney function than creatinine alone, and a provider reads it over time.
- Why it’s measured: To estimate kidney filtering from your creatinine, age, and sex.
- BUN/creatinine ratio
- This ratio compares your BUN result with your creatinine result. The lab calculates it from the two numbers rather than measuring it separately. A provider may look at it to help sort out whether a change in kidney numbers relates to hydration, diet, or kidney function.
- Why it’s measured: Adds context when BUN or creatinine is outside the reference range.
How it works
- Step 1
Order online
Check out here. A licensed clinician in your state reviews your order and sends it to the lab.
- Step 2
Visit a lab
Bring a photo ID to any of 2,000+ lab locations. No fasting needed, and nothing is due at the lab.
- Step 3
Get your results
Results post to your account, usually in 1 to 2 days, each number next to the lab’s reference range.
Find a lab near you
Choose from 2,000+ lab locations nationwide. Your order works at any of them.
What your results tell you
BUN and creatinine are reported in mg/dL, eGFR as an estimated filtration rate, and the ratio as a number, each compared with the lab’s range.
- Each marker next to the lab’s reference range
- Explained in plain language
- A licensed clinician reviews your order and, if appropriate, orders the test.
- A lab report you can download and share
A ratio outside the range has several possible causes, inside and outside the kidneys, so review it with a healthcare provider.
Clinical-grade testing, from the comfort of home.
From the lab to your report, every step of our process meets the gold standard in medical testing.
CLIA-certified labs
Every lab we partner with is certified under the Clinical Laboratory Improvement Amendments, meeting both state and federal standards with regular independent inspections.
We protect your health data
We protect your health data with encryption and do not sell it. Some results must be reported to public health authorities by law. See our Privacy Notice.
Rigorous quality assurance
All partner labs run regular internal quality checks, participate in proficiency testing, and comply with federal and state lab regulations.
Clinician-reviewed reports
Results are reviewed by an independent, licensed clinician.
Related tests
Questions
Common questions.
Anything else, our care team answers by phone, text, or email.
BUN and creatinine are both cleared by the kidneys, but BUN also changes with hydration, blood flow to the kidneys, and how much protein the body is breaking down. Comparing the two can point a healthcare provider toward a cause.
The ratio can rise with reduced blood flow to the kidneys or a recent blockage of urine flow, and fall when the body makes less urea, as in liver disease.
eGFR stands for estimated glomerular filtration rate. It is calculated from your creatinine result, age, and sex to estimate how well your kidneys filter blood. It is an estimate, and a healthcare provider reads it with your other results and history.
No. The ratio gives context, not a diagnosis. In most longer-term kidney conditions, the ratio stays in its usual range, so a ratio within the range does not mean your kidneys are fine. That is why it is read with creatinine and eGFR rather than alone.
Lab tests are informational and don’t diagnose conditions on their own. Available to adults 18 and older; test availability varies by lab location. A licensed clinician reviews your order and, if appropriate, orders the test. All testing is performed at CLIA-certified laboratories. Not for emergencies: if you think you may be having a medical emergency, call 911.