What is Glomerular Filtration Rate (GFR) test? 

A GFR test is also known as the estimated GFR (eGFR) test or calculated GFR (cGFR) test. It estimates the amount of blood which passes through the glomeruli - a group of blood capillaries present in the kidney - in a minute. Glomeruli filter out waste products from the blood and prevent the loss of essential nutrients like proteins. GFR test is mainly done to check how well your kidneys are functioning. It also helps to determine the stage of chronic kidney disease in patients. 

An individual with healthy kidneys can filter about 189 litres of blood and produce approximately 1.9 litres of urine every day. 

GFR depends on various factors such as:

  • Age
  • Race
  • Gender
  • Height
  • Weight 

GFR can be estimated directly or it can be calculated indirectly by estimating blood creatinine levels. Creatinine is a metabolite of creatine - an organic compound which supplies energy to the muscle. The former is only excreted by the kidneys and hence can be used to assess glomerular filtration rate. 

If the kidney function is impaired, creatinine will not be excreted completely and gets accumulated in the blood. So by estimating the amount of creatinine excreted in the urine, GFR can be easily calculated.

  1. Why is a Glomerular Filtration Rate (GFR) test performed?
  2. How do you prepare for a Glomerular Filtration Rate (GFR) test?
  3. How is a Glomerular Filtration Rate (GFR) test performed?
  4. Glomerular Filtration Rate (GFR) test results and normal range

Your healthcare practitioner may order the GFR test if you are at a higher risk of developing kidney disease due to:

GFR test may also be ordered for people who show the following symptoms of kidney disease:

  • Decrease in urine quantity 
  • Puffiness around eyes 
  • Swelling in the face, wrists, abdomen, thighs or ankles
  • Foamy, bloody or coffee-coloured urine
  • Burning sensation or abnormal discharge during urination
  • Change in the frequency of urination at night 
  • Mid-back pain below the ribs
  • High blood pressure 
  • Urinating more or less often
  • Feeling itchy
  • Tiredness
  • Loss of concentration
  • Loss of appetite
  • Nausea and vomiting 
  • Swelling or numbness in hands and feet
  • Darkened skin
  • Muscle cramps

Additionally, this test is ordered periodically to monitor kidney function in people with chronic kidney disease.

You may be advised to fast overnight before this test. Avoid consuming meat a day before the test. Please inform your doctor if you are taking any prescription or over-the-counter medicines, illegal drugs, vitamins or supplements. Your doctor may ask you to temporarily stop certain drugs that may alter the test results. Medicines such as cimetidine, cephalosporin, gentamicin, cisplatin and cefoxitin can increase the creatinine level, whereas trimethoprim decreases it. However, do not stop any medicine without consulting the healthcare practitioner. Also, avoid exercising before the test. 

Your doctor or laboratory technician will draw a small blood sample from a vein in your arm and immediately send it to the laboratory for testing. 

This procedure usually takes less than three minutes. After the test, you may experience mild pain or bruising at the site of needle insertion; however, these symptoms will subside shortly after the test.

Normal results:

A normal GFR indicates that your kidneys are functioning properly. The glomerular filtration rate is reported in millilitres/minute/1.73 metre2 (mL/min/1.73 m2). 

In adults, the GFR is normally more than 90 mL/min/1.73 m2; however, it decreases with age even in the absence of kidney disease.

Based on age, the mean GFR is as follows:

Age (years) Mean GFR (mL/min/1.73 m2)
20-29 116
30-39 107
40-49 99
50-59 93
60-69 85
70 and above  75

Abnormal results:

Higher than normal GFR may occur in the following conditions:

  • Exercise
  • Pregnancy
  • High cardiac output syndromes

Low GFR indicates chronic kidney disease. By estimating the GFR, doctors can determine the stage of chronic kidney disease. The following table shows the relation between the GFR and the stage of kidney disease: 

Stages of kidney disease Description  GFR (mL/min/1.73 m2)
1 Kidney damage with normal kidney function  90 or higher 
2 Kidney damage with mild loss of kidney function  89-60 
3a Mild to moderate loss of kidney function  59-45 
3b Moderate to severe loss of kidney function  44-30
4 Severe loss of kidney function  29-15 
5 Kidney failure  <15 

Conditions that cause decreased GFR are:

Sometimes, an individual without kidney disease can show abnormal results due to:

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.


  1. National Kidney Foundation [Internet]. New York (NY): U.S. GFR Calculator
  2. National Kidney Foundation [Internet]. New York (NY): U.S. Frequently Asked Questions about GFR Estimates
  3. National Institute of Diabetes and Digestive and Kidney Diseases [internet]: US Department of Health and Human Services; Estimating Glomerular Filtration Rate
  4. National Institute of Diabetes and Digestive and Kidney Diseases [internet]: US Department of Health and Human Services; Reporting Glomerular Filtration Rate
  5. American Kidney Fund [Internet]. Maryland (U.S.A.). Tests for kidney disease
  6. Chau K, Hutton H, Levin A. Laboratory assessment of kidney disease: glomerular filtration rate, urinalysis, and proteinuria. In: Skorecki K, Chertow GM, Marsden PA, Taal MW, Yu ASL, eds. Brenner and Rector's The Kidney. 10th ed. Philadelphia, PA: Elsevier; 2016:chap 26.
  7. Landry DW, Bazari H. Approach to the patient with renal disease. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 114.
  8. Pagana.K.D, Pagana.T.J, Pagana.T.N. Mosby’s Diagnostic and Laboratory Test Reference. 14th ed. Pg: 303-305
  9. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests
  10. National Kidney Foundation [Internet]. New York (NY). U.S. Estimated Glomerular Filtration Rate (eGFR)
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