Glomerular filtration rate

Glomerular filtration rate (GFR) is a test used to check how well the kidneys are working. Specifically, it estimates how much blood passes through the tiny filters in the kidneys, called glomeruli, each minute.
How the Test is Performed？
A blood sample is needed. For information on how this is done,
The blood sample is sent to a lab, where the creatinine level is tested. The lab specialist uses combines your creatinine level with several other factors to estimate your glomerular filtration rate (GFR). Different formulas are used for adults and children. The formula will include some or all of the following:
· Age
· Creatinine measurement
· Gender
· Height
· Race
· Weight
Why the Test is Performed？
The GFR test measures how well your kidneys are filtering a waste called creatinine, which is produced by the muscles. When the kidneys aren't working as well as they should, creatinine builds up in the blood.
Your doctor may order this test if there are signs that your kidneys are not working properly. It may also be done to see how far kidney disease has progressed.
The test is recommended for people with chronic kidney disease and those at risk for it due to:
· Diabetes
· Family history of kidney disease
· Frequent urinary tract infections
· Heart disease
· High blood pressure
· Urinary blockage
According to the National Kidney Foundation, normal results range from 90 - 120 mL/min/1.73 m2. Older people will have lower normal GFR levels, because GFR decreases with age.
Levels below 60 mL/min/1.73 m2 for 3 or more months are a sign of chronic kidney disease. A GFR result below 15 mL/min/1.73 m2 is a sign of kidney failure and requires immediate medical attention.
Considerations
The creatinine clearance test, which involves a 24-hour urine collection, can also provide an estimate of kidney function. However, this method is not always accurate.

GFR can increase during pregnancy.