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Estimated Glomerular Filtration Rate (GFR) Calculator

This PatientPlus article is written for healthcare professionals so the language may be more technical than the condition leaflets. You may find the abbreviations list helpful.

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.

Estimated Glomerular Filtration Rate Calculator
Abbreviated MDRD Equation
Gender
Black ethnicity?
Age in years
Plasma creatinine umol/l
Estimated GFR (ml/min/1.73m2):
Interpretation (CKD Stage)

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.

Notes

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).

Calculator above uses the abbreviated MDRD equation:1
Estimated GFR (ml/min/1.73m2) = 186 x (Creat / 88.4)-1.154 x (Age)-0.203 x (0.742 if female) x (1.210 if black)

  • 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

Stages of Chronic Kidney Disease6

Stages of Chronic Kidney Disease (CKD)

Use the suffix (p) to denote the presence of proteinuria when staging CKD.
StageGlomerular Filtration Rate
Values are normalized to an average surface area (size) of 1.73m2		DescriptionManagement
I90+Normal renal function
(but urinalysis, structural abnormalities or genetic factors indicate renal disease)		Observation and control of blood pressure
II60-89Mildly reduced renal function
(Stage 2 CKD should not be diagnosed on GFR alone - but urinalysis, structural abnormalities or genetic factors indicate renal disease)		Observation, control of blood pressure and cardiovascular risk factors
IIIa45-59Moderate decrease in renal function, with or without other evidence of kidney damageObservation, control of blood pressure and cardiovascular risk factors
IIIb30-44Moderate decrease in renal function, with or without other evidence of kidney damageObservation, control of blood pressure and cardiovascular risk factors
IV15-29Severely reduced renal functionPlanning for endstage renal failure
V<15Very severe (endstage) renal failureTransplant or dialysis

Document references

  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.

Internet and further reading

Acknowledgements

EMIS is grateful to Dr Huw Thomas for writing this article. The final copy has passed scrutiny by the independent Mentor GP reviewing team. ©EMIS 2010.
Document ID: 1087
Document Version: 26
Document Reference: bgp1093
Last Updated: 27 Oct 2009
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