Understanding Kidney Function Tests: What Does It All Mean?

Kidneys fil­ter waste and water out of your blood to cre­ate urine daily, functioning as an organ powerhouse. However, waste collects in the body when the kidneys cannot filter your blood efficiently, causing different forms of chronic kidney disease (CKD). The best way to know how healthy your kidneys are is through laboratory testing, and the sooner you get tested, the earlier you can get treated to help preserve your health. Getting lab work done can be confusing, so here is a breakdown to help you understand your blood work better.

There are many types of kidney function tests, and they can be categorized into two types: blood tests and urine tests.

Blood Tests:

1. Blood Urea Nitrogen (BUN)

   1. Blood urea nitrogen is a waste product that is formed when your body breaks down proteins. BUN tests measure the amount of urea nitrogen in your blood.

2. Serum Cre­a­ti­nine

   1. Creatinine is a breakdown product of creatine phosphate from muscle and protein metabolism. It is released at a constant rate by the body. Serum creatinine tests are often commonly used alongside the BUN test. 

3. Estimated Glomerular Filtration Rate (eGFR)

   1. eGFR tests are a snapshot of your kidney’s filtering power by estimating how much blood your kidneys filter per minute.

Urine Tests:

4. Urine Albumin-Creatinine Ratio (uACR)

   1. uACR tests measure the ratio between albumin (a type of protein) and creatinine that's present in your blood. It helps catch early signals of kidney disease and can catch these issues before they become serious.

5. Dipstick Urine Test

   1. The dipstick urine test tests for abnormal levels of different substances in your urine, like protein, glucose, etc. If your dipstick urine tests show abnormal results, your healthcare provider may follow up with further testing like a uACR.

      
      
      
      

What do the numbers mean?

Once you have received your results, it is important to understand that there is a “normal range” for each blood/urine test. If your numbers fall out of that normal range, it may indicate that you have a kidney problem, and it is important to contact your healthcare provider. Below is an example of average eGFRs for certain age ranges. To understand what your tests mean more, the Kidney Test Results fact sheet is a source that can provide expert-level knowledge and insight on interpreting your results.

Overall, getting kidney function tests and lab work done can be a whirlwind of confusion, but it is important for your health. These tests can help both you and your healthcare provider better understand the health status of your kidneys and ensure you can live a healthy life.