URR Calculator  Urea Reduction Ratio
The URR calculator allows you to check whether the performed dialysis was of good quality  adequate to the patient's state  using the urea reduction ratio (URR) calculations.
Follow the short text below to remind yourself about the most important issues connected to the URR lab tests, the use of URR in dialysis, and its basic formula.
We'll also refresh your knowledge on the hemodialysis adequacy guidelines. 🚰
What does URR stand for, and how to use it?
The URR is an abbreviation for the urea reduction ratio  we can also call it the urea reduction percentage (PRU). You should measure it every month or on every 12th dialysis session.
URR is a simple method for assessing the quality of dialysis (a lifesaving treatment used in the final stage of kidney failure). It is directly connected to the patient's outcome. The URR assesses the ability of the dialysis to eliminate the waste products from the blood. Because of its simplicity, this ratio can also be used for various comparisons, within one patient's results or the entire nations' dialysis standards.
URR is also closely related to the Kt/V equation both of these values can be used as dialysis adequacy tests (you can read more about Kt/V in the paragraph below, or in a separate Kt/V dialysis calculator).
❗ The dialysis is considered to be adequate, only if the URR ratio is greater than or equal to 65% (≥65%). 
The studies have confirmed that patients with lower than adequate URR values had more health problems and a greater risk of death.
What can we do to increase the URR?
 Increase time on dialysis
 Increase blood flow through the dialyzer  it's the case of both the dialyzer and the quality of the patient's blood vessels.
 Find and eliminate any circulation problems
Interested in the topic? Omni has plenty of useful tools to offer:
How to calculate URR in dialysis?
The URR calculations for dialysis are straightforward, and you can easily perform them singlehanded! In this section, we'd like to present two different versions of the urea reduction ratio formula  choose the one that suits you best.

URR = [(U_{pre}  U_{post})/U_{pre}] * 100%

URR = [1  (U_{post}/U_{pre})] * 100%
where:
 URR is the Urea Reduction Rate, given in %;
 U_{pre} stands for the urea level before the dialysis; and
 U_{post} stands for the urea level after the dialysis.
💡 The choice of urea units is wide (mg/dL, mg%, mg/L, g/L, g/dL); you only need to remember to use the same unit for both urea values. 
For example, if a patient's urea level before the dialysis is equal to 40 mg/dL, and afterward is lower than 20 mg/dL, we can perform the following URR calculations:
URR = [(40 mg/dL  20 mg/dL)/ 40 mg/dL] * 100%
URR = [20/ 40] * 100%
URR = ½ * 100% = 50%
Our URR is lower than 65%, which means that the performed dialysis was not adequate.
Still hungry for knowledge? 🍰=📚 Check one of our brilliant, topicrelated tools:
 FEUrea for Acute Kidney Injury (AKI)
 BUN/ creatinine ratio for prerenal causes of AKI
 Protein creatinine ratio
URR versus Kt/V
URR can also be calculated using the Kt/V equation for dialysis; we can put the relationship between these two values into the following equation:
(K * t)/V= ln(1  URR)
,where:
 K means the dialyzer clearance; describes the blood flow rate in milliliters per minute (mL/min);
 t is the time of dialysis in minutes;
 V stands for total body fluid volume;
 URR is the short version of Urea Reduction Ratio, given in %; and
 ln is used in mathematics to indicate the use of natural logarithm.