Renal Function Tests (Kidney Function Tests)
Overview
Kidney function tests measure how efficiently your kidneys are working. Most of these tests check how well your kidneys clear waste from your system. A kidney test may involve a blood test, a 24-hour urine sample, or both. You usually have your test results on the same day or within a few days.
Kidney function tests are either urine or blood tests that evaluate how well your kidneys are working. Most of these tests measure the glomerular filtration rate (GFR), which assesses how efficiently your kidneys clear waste from your body.
What are the types of kidney function tests?
Your healthcare provider may order one or more of the following kidney function tests:
Blood Tests for Kidney Function:
- Blood Urea Nitrogen (BUN): Measures the amount of nitrogen (produced from protein breakdown) in your blood.
- Estimated GFR (eGFR): Calculates your kidney’s filtration rate based on protein levels, age, gender, size, and race.
- Serum Creatinine: Looks for the buildup of creatinine, a waste product produced from muscle tissue breakdown.
Urine Tests for Kidney Function:
- Microalbuminuria: Detects a specific protein called albumin in your urine.
- Urinalysis: Analyzes urine for blood, proteins, and overall kidney function.
Test Details
What happens during a kidney urine test?
A 24-hour urine test is conducted at home. Your healthcare provider will provide you with a container to collect your urine. Here's what to expect:
- Urinate into the toilet as usual after you first wake up on the day of the test.
- For the rest of the day, collect your urine in the container.
- On the second day, collect your first urine sample of the day in the container.
- Return the container with the urine sample to your healthcare provider’s office or laboratory.
What happens during a kidney blood test?
For a blood test, you will visit your provider's office or a laboratory. A healthcare professional will use a small needle to draw a sample of your blood for testing.
What can I expect after a kidney test?
Kidney function tests are simple and typically have no side effects. After a blood test, you may experience:
- Bruising
- Dizziness
- Fatigue
Blood and urine tests generally don’t cause long-term pain or complications. If you experience any ongoing pain, fatigue, or other symptoms after the test, contact your healthcare provider.
Results and Follow-Up
When will I receive the results of my kidney function test?
How soon you receive your results can vary. In some cases, your provider may discuss your results on the same day. If the test is sent to a lab, results may take a few days.
What if my test results show early signs of kidney disease?
If your test results are abnormal, your healthcare provider will discuss potential treatment options. This may include medications to manage blood pressure or a referral to a nephrologist (a kidney specialist). You may also need more frequent kidney function tests to monitor your condition over time and track any underlying issues.