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2693 pages added, reviewed or updated during the last month (last updated: 14/4/2021)

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glomerular filtration rate (GFR)

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The glomerulus produces a selective ultrafiltrate of the blood. The rate of ultrafiltration is called the glomerular filtration rate which is about 120 ml/min or 170 litres per day. This is written 120 ml/min/1.73m2, to emphasise the fact that the rate is closely related to the body surface area.

The glomerular filtration rate increases from birth - in the neonate it is about one millilitre per minute.

In children the GFR may be estimated from the plasma creatinine as follows:

GFR = height (in cm) x 40 / plasma creatinine

In adults, there are various methods that may be used to estimate GFR:

Cockcroft-Gault equation is often used as a method of estimating GFR (although it was developed as a method of predicting creatinine clearance) from knowledge of serum creatinine, age and weight:

  • creatinine clearance = (((140 - age in years) x (wt in kg)) x 1.23) / (serum creatinine in micromol/l)

For women multiply the result of calculation by 0.85.The calculation is unreliable if the patient has unstable renal function, is very obese, or is oedematous.

An alternative is the 4-variable Modification of Diet in Renal Disease (MDRD) equation (1):

  • GFR (mL/min/1.73m2) = 186 x {[serum creatinine (µmol/L)/88.4] ^-1.154} x age (years) ^-0.203
    • x 0.742 if female and x 1.21 if African-Caribbean

NICE suggest that clinicians should use the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation to estimate GFRcreatinine, using creatinine assays with calibration traceable to standardised reference material:

consider using eGFRcystatinC at initial diagnosis to confirm or rule out CKD in people with:

  • an eGFRcreatinine of 45-59 ml/min/1.73 m2, sustained for at least 90 days and
  • no proteinuria (albumin:creatinine ratio [ACR] less than 3 mg/mmol) or other marker of kidney disease


  • the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) have developed equations to calculate eGFR based on serum creatinine (referred to as CKD-EPI2009Scr) and serum creatinine plus serum cystatin C (CKD-EPI2012Scr-cys)
  • in patients with near-normal kidney function, the Modification of Diet in Renal Disease (MDRD) equations underestimate GFR
    • the CKD-EPI2009Scr equation partly overcomes the major limitation of the MDRD equation
    • the CKD-EPI working group has two newer CKD-EPI equations:
      • one using cystatin C concentration (CKD-EPI2012cys) and the other using both cystatin C and serum creatinine concentrations (CKD-EPI2012Scr-cys)
      • they validate the new equations represent an advance over currently available equations across the range of GFR and in relevant subgroups
        • the advance even holds true among participants with an extreme body-mass index of less than twenty. The two new equations even have been recommended by KDIGO 2012Clinical Practice Guidelines for the Evaluation and Management of CKD (3)
        • there has been data that the CKD-EPI2012Scr-cys is superior to calculations based on serum creatinine alone (4,5,6)
          • a study in Chines population ((n = 788; median age, 54 [range, 19-94] years)) concluded (7) '..CKD-EPI2012Scr-cys appeared less biased and more accurate in overall participants. Neither of the new CKD-EPI equations achieved ideal accuracy in senior participants with moderately-severely injured GFR...'
        • a review states that overall, the CKD-EPICR-CYS equation had better precision and accuracy than that based on creatinine alone or CysC alone (8)
  • GFR estimates between 60 and 89 mL/min/1.73 m2 do not indicate chronic kidney disease unless there is other laboratory/clinical evidence of disease
  • there is no need to collect 24 h urine samples to measure creatinine clearance in primary care
  • in cases where there are extremes of muscle mass - for example, in bodybuilders, amputees or people with muscle wasting disorders - interpret the eGFR with caution
    • reduced muscle mass will lead to overestimation and increased muscle mass to underestimation of the GFR
  • advise people not to eat any meat in the 12 hours before having a blood test for GFR estimation. Avoid delaying the despatch of blood samples to ensure that they are received and processed by the laboratory within 12 hours of venepuncture


Last edited 10/2019 and last reviewed 10/2019