GFR: How is it Done and What is the Purpose of This Kidney Test?

GFR: How is it Done and What is the Purpose of This Kidney Test?

Bajaj Finserv Health
December 23, 20214 mins read

Key Takeaways

  • A GFR test will help determine how well your kidneys are functioning
  • On average your kidneys filter about half a cup of blood in a minute
  • Your GFR normal value is dependent on your age, gender and ethnicity

A glomerular filtration rate test is done to determine how much blood your kidneys filter. It is also known as GFR. Your kidneys have filtering units known as nephrons. These units have a glomerulus and a tubule. Glomerulus filters your blood and tubules return the needed substance to the blood as well as removes the waste.Glomerular filtration rate is a blood test that checks the amount of blood filtered in a minute. On average your kidneys filter about half a cup of blood in a minute [1].

The glomerular filtration rate is estimated with the help of a glomerular filtration rate calculator. Since it is an estimated rate, it is also known as eGFR. The GFR calculator has a mathematical formula that will determine the filtration rate. Calculating GFR will include your creatinine levels and other factors such as age, gender, weight, and more. Creatinine level is measured from the blood drawn for a GFR. 

In a glomerular filtration test, your doctor will take a sample of your blood for testing. The sample is then sent to the lab for testing. Be sure to tell your doctors if you are taking any medication or if you are pregnant. These factors may affect your GFR. Your doctor may even tell you to stop your medication before the test.

To know more about why the GFR test is done and what it diagnoses, read on.


Kidney diseases do not usually show symptoms at early stages. This is why your doctor may recommend a GFR test if you have the risk factors of kidney failure. These risk factors may include the following:

  • Family history of chronic kidney failure
  • High blood pressure
  • Diabetes
  • Overweight
Additional read: Sugar Test: Important Things to Know About Blood Test for DiabetesGFR kidney test

Your doctor may also recommend this kidney functionality test if there are obvious signs of kidney failure. These signs may include:

  • Muscle cramps
  • Vomiting or nausea
  • Fatigue
  • Loss of appetite
  • Itching 
  • Swelling in your limbs
  • Increase or decrease in urination frequency


Your glomerular filtration test will help doctors diagnose if you have chronic kidney disease or not. If your GFR is normal/average, you may not have chronic kidney failure. However, if your GFR is under the normal value you may have kidney disease. It is important to remember that an abnormal value of GFR does not necessarily mean that you have kidney failure. The opposite is also true as a normal GFR does not ensure that you do not have a kidney disease. 

GFR test also helps determine the stage of chronic kidney failure. There are 5 stages of chronic kidney failure. They are categorized on the basis of your glomerular filtration rate

The kidney functionality test may also help your doctor determine how you are responding to the treatment. It may also help check the trend of your GFR. Based on these numbers, doctor may form a treatment plan that will help maintain your GFR value or ensure that it does not fall down any further. 

Normal Range

Your GFR normal value may change based on various factors such as weight, height, gender, age, and ethnicity. However, the average GFR in adults is 90 or higher. The glomerular filtration may decrease as you get older. Based on your age, the following may be your average eGFR [2].

For ages 20-29, your average GFR may be 116. From 30-39 years, your average GFR may decline to 107. It may further decline if your age is between 40 and 49 years. Your average GFR would then be 99. If you are between 50 and 59 years, your average GFR may be 93. This may further decline to 85 at 60-69 years, dropping as low as 75 once you cross 70 years of age. 

Additional read: What are Kidney Stones and How to Avoid Them

Kidney disease may be prevented by taking proper care of your health. High blood pressure and diabetes are the most common causes of chronic kidney failure [3]. If you see any signs of kidney disease, talk to your doctor immediately. You can prevent kidney failure with early detection. Book an appointment with the best practitioners on Bajaj Finserv Health and get ahead of such health issues. Find a wide range of test packages and stay proactive about preventive care with ease. Access quality care across a wide range of network healthcare partners and enjoy special deals on care too!

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Please note that this article is solely meant for informational purposes and Bajaj Finserv Health Limited (“BFHL”) does not shoulder any responsibility of the views/advice/information expressed/given by the writer/reviewer/originator. This article should not be considered as a substitute for any medical advice, diagnosis or treatment. Always consult with your trusted physician/qualified healthcare professional to evaluate your medical condition. The above article has been reviewed by a qualified doctor and BFHL is not responsible for any damages for any information or services provided by any third party.

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