Last Updated on April 4, 2025 by Analgesia team
What is Normal GFR
GFR stands for glomerular filtration rate, which is a measure of how well your kidneys are working. The test checks for kidney disease by measuring how much blood your kidneys filter each minute.
What it is
GFR measures the amount of blood filtered by the glomeruli in your kidneys per minute. The glomeruli are tiny blood vessels in the kidneys that act as filters, removing waste products and excess substances while retaining essential proteins and cells.
Why is Glomerular Filtration Rate Important?
GFR is a key indicator of kidney health. It helps diagnose and monitor conditions like chronic kidney disease (CKD) and assess the severity of kidney damage. A normal GFR ensures that your body maintains a healthy balance of fluids, electrolytes, and waste products.
How it’s measured
GFR can be measured directly, but this process is complex and time-consuming. Instead, it’s often estimated using a formula that incorporates:
- Creatinine levels: A waste product in the blood.
- Age, sex, and body size: These factors influence creatinine levels and kidney function.
This calculation is known as the estimated GFR (eGFR). A simple blood test is used to measure creatinine, and the eGFR is derived from this.
A normal Glomerular Filtration Rate for an adult male is 90 to 120 mL/min, but it varies by age.
GFR stages
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- Stage 1: GFR of 90 or higher, with few or no symptoms
- Stage 2: GFR of 60–89, which may be normal for some people without kidney damage
- Stage 3: GFR of 30–59, which can cause anemia, high blood pressure, and early bone disease
- Stage 4: GFR of 15–29, which indicates severe kidney disease
- Stage 5: GFR of 15 or lower, which indicates end-stage renal disease (ESRD)
What are Normal GFR Levels?
- 90 mL/min or higher: Normal kidney function.
- 60–89 mL/min: Mildly reduced kidney function, often without symptoms.
- Below 60 mL/min: Indicates potential kidney disease.
- Below 15 mL/min: Signals kidney failure, requiring immediate medical attention.
Factors Affecting Glomerular Filtration Rate
- Age: GFR naturally declines with age.
- Health Conditions: Diabetes, high blood pressure, and kidney infections can lower GFR.
- Medications: Certain drugs can impact kidney function and GFR levels.
GFR and kidney disease
- A Glomerular Filtration Rate below 60 for three months or more indicates chronic kidney disease (CKD)
- A Glomerular Filtration Rateof 15 or lower indicates kidney failure, which requires immediate medical attention
The Difference Between eGFR and Measured GFR
Measured GFR (mGFR) is considered the most accurate method for assessing kidney function. It involves injecting a marker substance, such as inulin or iohexol, into the bloodstream and monitoring its clearance rate from the body. This direct measurement precisely reflects the filtration capacity of the kidneys. However, mGFR requires specialized equipment, is time-intensive, and is often reserved for research or cases where absolute precision is necessary.
In contrast, estimated GFR (eGFR) is calculated using a formula that incorporates serum creatinine levels, age, sex, and race. eGFR is less invasive and more practical for routine clinical use, as it only requires a blood test to measure creatinine. While it’s highly effective for identifying kidney dysfunction in most patients, eGFR is an approximation and may be less accurate in certain populations, such as those with unusual muscle mass or extreme body sizes. Ultimately, eGFR is widely used in clinical settings due to its simplicity and accessibility.