What is eGFR?

Estimated Glomerular Filtration Rate (eGFR) is a test used to assess how well your kidneys are functioning. It estimates the amount of blood that gets filtered by the glomeruli (tiny filters in the kidneys) each minute. The following image depicts the complexity of the kidney, starting with the nephron.

National Institute of Diabetes and Digestive and Kidney Diseases - Glomerular Disease

The nephron is the basic structural and functional unit of the kidney, responsible for the vital process of filtering blood, removing waste products, and regulating water and solute balance in the body. Each human kidney contains approximately one million nephrons, which work collectively to perform the kidney's complex functions. The structure of a nephron is specially designed to efficiently filter blood, reabsorb necessary nutrients and water, and excrete waste products in the form of urine.

The glomerulus plays a crucial role within the kidney as a component of the nephron. The glomerulus is a network of tiny blood vessels (capillaries) located at the beginning of the nephron. Its roles include:

  1. Blood Filtration: The glomerulus is where the filtration of blood begins. Blood pressure forces water, salt, glucose, amino acids, and waste products (like urea and creatinine) from the blood through the capillary walls and into the Bowman's capsule, another part of the nephron that collects the filtrate. The filtrate then travels through the rest of the nephron, where further processing occurs.
  2. Prevention of Protein Loss: The structure of the glomerulus prevents large molecules, such as proteins and blood cells, from being filtered into the urine, retaining them within the bloodstream.

The eGFR is calculated based on your blood creatinine level, age, body size, and gender. This calculation provides a critical insight into the kidney's health, indicating how efficiently they're filtering waste from your blood.

Unlike direct measurements of kidney function, which can be invasive and complex, eGFR offers a simple and non-invasive way to monitor kidney health. It's a crucial part of any comprehensive health assessment, particularly for those with risk factors for kidney disease, such as hypertension, diabetes, or a family history of kidney failure.

Why is eGFR Important?

The primary importance of eGFR lies in its role in detecting and monitoring kidney disease. According to the National Kidney Foundation, 33% (1 in 3 people) of American adults are at risk for kidney disease. Healthy kidneys ensure the removal of toxins and waste materials from the blood, maintaining a delicate balance of body fluids and electrolytes. A decline in eGFR can indicate a reduction in kidney function, signaling acute or chronic kidney disease (CKD). In addition to CKD, impaired kidneys can cause heart disease, heart attack and stroke, high blood pressure, weak bones, nerve damage, and low red blood cell count.

Monitoring eGFR levels is essential for diagnosing conditions that affect kidney function, assessing the severity of kidney damage, and guiding the management and treatment of kidney-related disorders. It's particularly important for individuals with conditions that can impair kidney function, including diabetes, high blood pressure, and heart disease.

Understanding Your eGFR Test Results

eGFR results are typically reported in milliliters per minute per 1.73 m² (mL/min/1.73 m²). When interpreting eGFR results, this table from the National Kidney Foundation illustrates how even normal kidney function could accompany kidney damage:

National Kidney Foundation - eGFR: A key to understanding how well your kidneys are working

The UK Kidney Association states that an eGFR of ~100 and up to 120 mL/min/1.73 m² is healthy. It's important to note that eGFR is an estimate of kidney function and must be interpreted within the context of other clinical findings and patient factors. For example, a mildly decreased eGFR in an elderly individual without any other signs of kidney disease may be considered normal aging. Conversely, even a slight decrease in eGFR in a young adult may warrant further investigation. American Kidney Fund recommends discussing your eGFR results with your doctor, and doing so immediately if your levels are 60 or less is very important.

Improving eGFR and Kidney Function

While improving renal function is not easy, it is possible. A study from 2013 found that it is possible to improve renal function at any stage of CKD!

In addition to staying healthy through weight management, regular exercise, following a balanced diet, and practicing healthy habits (quitting smoking and limiting alcohol intake), the National Kidney Foundation also recommends that people with kidney disease should:

  • Lower high blood pressure
  • Manage blood sugar levels
    • The CDC states that high blood sugar (linked to diabetes) can inhibit kidney function by damaging blood vessels in the nephrons.
  • Reduce salt intake
    • Action on Salt states that a high salt diet can disrupt the balance of sodium and limit kidney function, promoting high blood pressure and straining the kidneys.
  • Avoid NSAIDs (type of painkiller)
    • According to the American Journal of Kidney Diseases, NSAIDs can harm kidney function by reducing blood flow and prostaglandin (maintains GFR and renal blood flow) production, impairing sodium and water excretion, leading to acute kidney injury.
  • Moderate protein consumption
    • A study from 2018 suggests that since high protein intake can damage glomeruli, a low protein diet can preserve renal function in those who have CKD.
  • Get an annual flu shot
    • The CDC emphasizes the importance of the flu vaccine for people with CKD who are “at high risk of developing serious flu complications”.

Additionally, exercise therapy and certain dietary patterns may be associated with a lower rate of eGFR decline.

Where Can I Learn More?

American Kidney Fund - Blood Test: eGFR

National Institute of Diabetes and Digestive and Kidney Diseases - Your Kidneys & How They Work

UK Kidney Association - About eGFR

National Kidney Foundation - eGFR: A key to understanding how well your kidneys are working

Scientific Literature

Cai Q, Dekker LH, Bakker SJL, de Borst MH, Navis GJ. Dietary Patterns Based on Estimated Glomerular Filtration Rate and Kidney Function Decline in the General Population: The Lifelines Cohort Study. Nutrients. 2020 Apr 16;12(4):1099. doi: 10.3390/nu12041099.

Kamyar Kalantar-Zadeh, Holly M Kramer, Denis Fouque, High-protein diet is bad for kidney health: unleashing the taboo, Nephrology Dialysis Transplantation, Volume 35, Issue 1, January 2020, Pages 1–4,

Tang R, Kou M, Wang X, et al. Self-Reported Frequency of Adding Salt to Food and Risk of Incident Chronic Kidney Disease. JAMA Netw Open. 2023;6(12):e2349930. doi:10.1001/jamanetworkopen.2023.49930

Zhang, L., Wang, Y., Xiong, L. et al. Exercise therapy improves eGFR, and reduces blood pressure and BMI in non-dialysis CKD patients: evidence from a meta-analysis. BMC Nephrol 20, 398 (2019).