Estimated Glomerular Filtration Rate (GFR) Calculator

There are several equations available for estimating GFR.
This calculator uses the abbreviated MDRD equation¹ (MDRD = Modification of Diet in Renal Disease Study), which is the one recommended by NICE² and The Renal Association (UK).³
See the accompanying clinical record Assessing Kidney Function.

Use the eGFR value calculated by your local laboratory in preference to the above as it is likely to be more accurate (as it may adjust for variations in creatinine measurements).

• Serum creatinine is correlated with muscle mass and therefore estimation of GFR using prediction equations in people with extremes of muscle mass is subject to inaccuracy. In those with increased muscle mass, GFR will be under estimated and in those with reduced muscle mass GFR will be over estimated.²
• This equation is accurate in patients with chronic kidney disease (CKD), but it significantly underestimates GFR in healthy persons (probably due to the exclusion of healthy persons from the study used to develop this equation).⁴ Do not over-interpret slightly low values.
• Stages 1 or 2 CKD should not be diagnosed on GFR alone - unless there are urinalysis, structural abnormalities or genetic factors to indicate renal disease.
• These calculations assume that the creatinine levels are relatively stable (over a few days) and not rapidly changing.
• The MDRD equation is not valid for children - use the Counahan-Barrat method.⁵

The calculator is based on the equation described in Levey AS, Bosch JP, Lewis JB, et al; A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Modification of Diet in Renal Disease Study Group. Ann Intern Med. 1999 Mar 16;130(6):461-70.

1. Levey AS, Bosch JP, Lewis JB, et al; A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Modification of Diet in Renal Disease Study Group. Ann Intern Med. 1999 Mar 16;130(6):461-70. [abstract]
2. Chronic kidney disease, NICE Clinical Guideline (September 2008); Early identification and management of chronic kidney disease in adults in primary and secondary care
3. The Renal Association (UK) website
4. Rule AD, Larson TS, Bergstralh EJ, et al; Using serum creatinine to estimate glomerular filtration rate: accuracy in good health and in chronic kidney disease. Ann Intern Med. 2004 Dec 21;141(12):929-37. [abstract]
5. Counahan-Barrat method - see Nephron.com website.
6. No authors listed; K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. Am J Kidney Dis. 2002 Feb;39(2 Suppl 1):S1-266.

• The Renal Association (UK) website
• UK National Kidney Federation