# URR Calculator - Urea Reduction Ratio

*“The urea reduction ratio and serum albumin concentration as predictors of mortality in patients undergoing hemodialysis“*The New England journal of medicine (September 1993)

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**. 🚰

*We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace professional medical advice.*

## 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 life-saving 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 nation's 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. For instance, you can use GFR calculator for detecting a kidney disease at its early stage and urine output calculator for computing fluid balance and urine output rate (ml/kg) per hour.

## How to calculate URR in dialysis?

The URR calculations for dialysis are straightforward, and **you can easily perform them single-handed!** In this section, we'd like to present two different versions of the urea reduction ratio formula - **choose the one that suits you best**.

💡 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, topic-related tools, such as FEUrea for Acute Kidney Injury (AKI) and BUN/ creatinine ratio for prerenal causes of AKI.

## 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.

**Kt/V vs. URR relationship**, try the Kt/V calculator.