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Dialysis: Measuring How Well It Works


Dialysis removes urea and other waste products from the blood. To find out how well dialysis is working, you will have blood tests that look at the level of urea in your blood. Usually these tests are done once a month, at the start of your session and again at the end. Two of the measures that show how well dialysis is working are Kt/V and urea reduction ratio (URR).


The most common way to measure how well dialysis is working is to calculate the amount of body fluid that is cleared of urea during each dialysis session. This is called the Kt/V.

  • Kt represents the amount of fluid that is cleared of urea during each dialysis session. It is measured in milliliters per minute (mL/min).
  • V represents the volume of water a person's body contains.

Urea reduction ratio

One way to measure how well dialysis is removing urea from the body is to measure blood urea nitrogen (BUN) level. The BUN is measured before and after your treatment session. Then the two numbers are compared to see how much the urea level in the blood has gone down. This difference is called the urea reduction ratio (URR).

The Kt/V and URR tests are not the only ways to tell how well dialysis is working. It's important to talk with your doctor and other care team members about how you are feeling.

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Current as of: October 11, 2023

Author: Healthwise Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.


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