What is a normal URR for hemodialysis?

KDOQI guidelines recommend a minimum URR of 65% per hemodialysis session. Values below 65% suggest under-dialysis and warrant review of blood flow rate, session duration, or access adequacy.

What units should I use?

Both mg/dL and mmol/L are supported. The ratio is dimensionless, so the result is identical regardless of which unit you choose — just be consistent between pre and post values.

Is URR the same as Kt/V?

No, but they are related. URR is a simpler bedside estimate of dialysis dose. Kt/V accounts for fluid removal and urea generation and is generally preferred for formal adequacy reporting, but URR ≥65% correlates well with Kt/V ≥1.2.

Why does my post-BUN need to be lower than pre-BUN?

Hemodialysis removes urea from the blood, so post-dialysis BUN should always be lower than pre-dialysis BUN in a successful session. If post ≥ pre, check whether the samples were drawn correctly.

Can I use this for peritoneal dialysis?

URR as calculated here is specific to hemodialysis. Peritoneal dialysis adequacy uses weekly Kt/V derived from 24-hour urine and dialysate collections.

Urea Reduction Ratio Calculator

Name: Urea Reduction Ratio Calculator
Availability: InStock
Author: Nham Vu

Enter pre- and post-dialysis BUN to calculate URR (%) and see whether the session met the ≥65% adequacy target.

BUN Values

Unit

Pre-dialysis BUN (mg/dL)

Post-dialysis BUN (mg/dL)

Result

Enter BUN values and click Calculate.

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Summary

Enter pre- and post-dialysis BUN to calculate URR (%) and see whether the session met the ≥65% adequacy target.

How it works

Enter the pre-dialysis BUN (blood urea nitrogen) value in mg/dL or mmol/L.
Enter the post-dialysis BUN measured at the end of the session.
Select the unit that matches your lab report.
The calculator applies URR = (Pre − Post) / Pre × 100%.
Results are displayed with color-coded interpretation: ≥65% is adequate per KDOQI guidelines.

Use cases

Nephrologists checking whether a hemodialysis session met the minimum URR target.
Dialysis nurses documenting treatment adequacy after each session.
Students and residents learning dialysis adequacy assessment.
Patients wanting to understand what their BUN numbers mean.
Dietitians correlating dialysis adequacy with nutritional lab trends.
Quality-improvement teams tracking URR across a dialysis unit.

Frequently Asked Questions

Last updated: 2026-07-26 · Reviewed by Nham Vu