# Estimated Glomerular Filtration Rate (GFR) Calculator

Professional Reference articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

There are several equations available for estimating GFR.
This calculator uses the abbreviated MDRD equation[1] (MDRD = Modification of Diet in Renal Disease Study), which is the one recommended by NICE[2] 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 Disease[6]

 Stages of Chronic Kidney DiseaseUse the suffix (p) to denote the presence of proteinuria when staging chronic kidney disease (CKD). Stage Glomerular Filtration RateValues are normalised to an average surface area (size) of 1.73 m2 Description Management I 90+ Normal renal function (but urinalysis, structural abnormalities or genetic factors indicate renal disease). Observation and control of blood pressure. II 60-89 Mildly 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. IIIa 45-59 Moderate decrease in renal function, with or without other evidence of kidney damage. Observation, control of blood pressure and cardiovascular risk factors. IIIb 30-44 Moderate decrease in renal function, with or without other evidence of kidney damage. Observation, control of blood pressure and cardiovascular risk factors. IV 15-29 Severely reduced renal function. Planning for end-stage kidney disease. V <15 Very severe (end-stage) kidney disease. Transplant or dialysis.

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