What is eGFR?

Last Updated: April 30, 2025

In this article:

• How is eGFR Calculated?

• What do eGFR Results Mean?

• Factors That Can Affect eGFR Accuracy

• What to Do if Your eGFR is Low?

• Takeaway

eGFR stands for estimated Glomerular Filtration Rate. It's a blood test to measure how well your kidneys filter waste and excess fluids from your blood. The eGFR is an essential indicator of kidney function and helps diagnose and monitor kidney disease.

How is eGFR Calculated?

eGFR is calculated using a formula that considers several factors, including:

• Serum Creatinine: A waste product in your blood that comes from muscle metabolism. Higher levels indicate reduced kidney function.

• Age: Kidney function naturally declines with age.

• Sex: Men generally have more muscle mass than women, which can affect creatinine levels.

What do eGFR Results Mean?

eGFR is reported in mL/min/1.73 m², representing the amount of blood filtered by the kidneys per minute per standardized body surface area. The results fall into different ranges, which correspond to the stages of chronic kidney disease (CKD):

eGFR (mL/min/1.73 m²)	Stage	Meaning
90 or higher	Stage 1	Normal or high kidney function, but signs of kidney damage may be present.
60-89	Stage 2	Mild loss of kidney function.
45-59	Stage 3a	Mild to moderate loss of kidney function.
30-44	Stage 3b	Moderate to severe loss of kidney function.
15-29	Stage 4	Severe loss of kidney function.
Less than 15	Stage 5	Kidney failure (End-Stage Kidney Disease or ESRD).

Why is eGFR Important?

• Early Detection: A declining eGFR can indicate early kidney damage before you have noticeable symptoms.

• Monitoring: If you have kidney disease, your eGFR helps track the progression of the disease.

• Guiding Treatment: Your eGFR level helps your doctor decide on treatments, such as medications, dietary changes, or when dialysis may be needed.

Factors That Can Affect eGFR Accuracy

eGFR is an estimate, so certain factors can influence the results:

• Muscle mass: People with high or low muscle mass may have inaccurate eGFR readings.

• Diet: High protein intake or recent vigorous exercise can temporarily raise creatinine levels, lowering eGFR.

• Pregnancy: Kidney function changes during pregnancy, so special care is needed when interpreting eGFR.

• Medications: Certain drugs can affect creatinine levels and, consequently, eGFR.

• Supplements: Like creatine can increase serum creatinine levels

What to Do if Your eGFR is Low?

If your eGFR is lower than normal, your doctor may recommend:

1. Further Testing: Urine tests to look for protein or blood in urine  and ultrasounds of kidneys  to assess the size and shape of kidneys.

2. Lifestyle Changes:

   • Reducing salt intake.

   • Decreasing processed food intake

   • Staying hydrated.

   • Managing blood pressure and blood sugar levels.

3. Medications: ACE inhibitors or ARBs may be prescribed to protect kidney function.

4. Regular Monitoring: Routine eGFR tests to track kidney function over time.

Takeaway

eGFR is a simple but crucial test for understanding how well your kidneys are functioning and filtering toxins. If your eGFR is low, it doesn’t necessarily mean immediate kidney failure—it’s a sign to work with your doctor on a plan to manage and protect your kidney health.