Various different diseases, conditions and medicines can affect the function of the kidneys. The estimated glomerular filtration rate (eGFR) does not diagnose any kidney disease but is a test to assess how well your kidneys are working.
What is the estimated glomerular filtration rate (eGFR)?
The eGFR is a test that is used to assess how well your kidneys are working. The test estimates the volume of blood that is filtered by your kidneys over a given period of time. The test is called the estimated glomerular filtration rate because the glomeruli are the tiny filters in the kidneys. If these filters do not do their job properly then the kidney is said to have reduced or impaired kidney function.
The eGFR test involves a blood test which measures a chemical called creatinine. Creatinine is a breakdown product of muscle. Creatinine is normally cleared from the blood by the kidneys. If your kidneys are not working properly, the level of creatinine in the blood goes up.
The eGFR is then calculated from your age, sex and blood creatinine level. An adjustment to the calculation is needed for people with African-Caribbean origin.
Stages of kidney function
The level of kidney function is divided into five stages:
Stage of Chronic Kidney Disease
eGFR ml/min/1.73 m
|Stage 1: the eGFR shows normal kidney function but you are already known to have some kidney damage or disease. For example, you may have some protein or blood in your urine, an abnormality of your kidney, kidney inflammation, etc.||90 or more|
|Stage 2: mildly reduced kidney function AND you are already known to have some kidney damage or disease. People with an eGFR of 60-89 without any known kidney damage or disease are not considered to have chronic kidney disease (CKD).||60 to 89|
|Stage 3: moderately reduced kidney function. (With or without a known kidney disease. For example, an elderly person with ageing kidneys may have reduced kidney function without a specific known kidney disease.)||45 to 59 (3A)|
30 to 44 (3B)
|Stage 4: severely reduced kidney function. (With or without known kidney disease.)||15 to 29|
|Stage 5: very severely reduced kidney function. This is sometimes called end-stage kidney failure or established renal failure.||Less than 15|
Note: it is not possible to assess the estimated glomerular filtration rate (eGFR) accurately in people with abnormal amounts of muscle and in people who have conditions that can affect the level of creatinine. This includes:
- People with muscle wasting conditions.
- People who have had an amputation of an arm or leg.
- Malnourished people.
- People with acute kidney failure.
- People with a lot of fluid retention (oedema).
Dr Tim Kenny
Dr Colin Tidy
Dr Adrian Bonsall