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title: "eGFR Blood Test Results Explained — Kidney Function Guide" slug: "egfr-blood-test-results-explained" description: "Understand your eGFR blood test results. Learn what estimated Glomerular Filtration Rate means, normal ranges by age, and what low eGFR indicates." date: "2026-03-14" category: "blood-tests" keywords: ["eGFR blood test", "glomerular filtration rate", "eGFR results", "kidney function test", "eGFR normal range"] reading_time: "8 min"

eGFR Blood Test Results Explained — Kidney Function Guide

Your eGFR (estimated Glomerular Filtration Rate) is the single most important number for assessing how well your kidneys are working. It estimates how many milliliters of blood your kidneys filter per minute, adjusted for body size. If you've had blood work that includes a creatinine level, your lab likely calculated an eGFR and printed it on your report.

This guide explains what eGFR measures, what the numbers mean, how age affects your results, and when a low eGFR should prompt a conversation with your doctor.

What Is eGFR?

The glomerular filtration rate (GFR) measures the volume of blood that passes through the glomeruli — tiny filters inside your kidneys — every minute. Because directly measuring GFR requires a complex procedure involving injected tracers and timed urine collections, labs instead calculate an estimated GFR using a formula based on your blood creatinine level, age, and sex.

Doctors order eGFR to screen for chronic kidney disease (CKD), monitor known kidney conditions, adjust medication dosages that depend on kidney function, and evaluate kidney health before surgery or imaging studies that use contrast dye.

The test itself requires only a standard blood draw. No fasting is needed. Your lab measures serum creatinine and then applies a mathematical formula to produce the eGFR value.

How Is eGFR Calculated?

Labs in the United States and most of the world now use the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation to calculate eGFR. In 2021, a major update removed the race coefficient from the formula, resulting in the 2021 CKD-EPI creatinine equation that is now recommended by the National Kidney Foundation and the American Society of Nephrology.

The formula uses three variables:

• Serum creatinine — a waste product from normal muscle metabolism, measured in mg/dL
• Age — eGFR naturally declines with age
• Sex — the equation uses different coefficients for males and females because of average differences in muscle mass

The older MDRD (Modification of Diet in Renal Disease) equation is still used by some labs but is less accurate at higher GFR levels. If your lab report shows an eGFR calculated by MDRD, the result may simply say ">60" rather than giving a specific number above 60.

Why the Race Coefficient Was Removed

Before 2021, the CKD-EPI equation included a race-based adjustment that produced higher eGFR values for Black patients. Research showed that this adjustment could delay diagnosis and treatment of kidney disease. The updated 2021 equation eliminates race from the calculation entirely, providing a single formula for all patients. This change means some patients may see a lower eGFR compared to results calculated with the older equation.

eGFR Normal Ranges

An eGFR result is reported in mL/min/1.73 m² (milliliters per minute per 1.73 square meters of body surface area).

| eGFR Value | Kidney Function | |---|---| | 90 or above | Normal kidney function | | 60–89 | Mildly decreased (may be normal for age in older adults) | | 45–59 | Mild to moderately decreased | | 30–44 | Moderately to severely decreased | | 15–29 | Severely decreased | | Below 15 | Kidney failure |

A single eGFR result between 60 and 89 in an otherwise healthy person — especially someone over 60 — does not necessarily indicate kidney disease. Kidney function naturally declines with age. An eGFR in this range is only considered significant if it persists over three or more months and is accompanied by other signs of kidney damage, such as protein in the urine (albuminuria).

How Age Affects eGFR

Average eGFR declines with age even in healthy individuals without kidney disease. The following approximate values represent typical averages for healthy adults:

| Age Range | Average eGFR (mL/min/1.73 m²) | |---|---| | 20–29 | 116 | | 30–39 | 107 | | 40–49 | 99 | | 50–59 | 93 | | 60–69 | 85 | | 70+ | 75 |

These are population averages. Individual variation is normal. A 72-year-old with an eGFR of 68 may have age-appropriate kidney function, while a 35-year-old with the same number would require further evaluation.

CKD Stages by eGFR

Chronic kidney disease is classified into stages based on eGFR along with markers of kidney damage (particularly albuminuria). The staging system, established by KDIGO (Kidney Disease: Improving Global Outcomes), guides treatment decisions.

| CKD Stage | eGFR (mL/min/1.73 m²) | Description | |---|---|---| | G1 | ≥ 90 | Normal or high GFR (CKD diagnosed only if kidney damage is present) | | G2 | 60–89 | Mildly decreased (CKD diagnosed only if kidney damage is present) | | G3a | 45–59 | Mild to moderate decrease | | G3b | 30–44 | Moderate to severe decrease | | G4 | 15–29 | Severe decrease | | G5 | < 15 | Kidney failure (dialysis or transplant may be needed) |

Stages G1 and G2 require evidence of kidney damage — such as albuminuria, abnormal kidney imaging, or a history of kidney transplant — to be classified as CKD. Stages G3 through G5 are defined by eGFR alone, regardless of whether other markers of damage are present.

What Low eGFR Means

A low eGFR means your kidneys are not filtering blood as efficiently as they should. The lower the number, the more significant the reduction in kidney function.

Common causes of a persistently low eGFR include:

• Diabetes — the leading cause of CKD worldwide. High blood sugar damages the kidney's filtering units over time.
• High blood pressure — the second most common cause. Uncontrolled hypertension damages the blood vessels in the kidneys.
• Glomerulonephritis — inflammation of the kidney filters, which can be caused by infections, autoimmune diseases, or other conditions.
• Polycystic kidney disease — a genetic condition where fluid-filled cysts grow in the kidneys and gradually reduce function.
• Prolonged use of nephrotoxic medications — including NSAIDs (ibuprofen, naproxen) taken regularly over long periods, certain antibiotics, and some chemotherapy drugs.
• Recurrent kidney infections or urinary obstruction — conditions that cause repeated damage to kidney tissue.

A single low eGFR reading does not always mean chronic kidney disease. Temporary drops can occur due to dehydration, acute illness, recent intense exercise, or certain medications. Your doctor will typically repeat the test in three months before making a diagnosis.

What High eGFR Means

An eGFR above 90 is considered normal. Very high eGFR values (above 120–130) are sometimes seen in the early stages of diabetic kidney disease, a phenomenon called hyperfiltration. In hyperfiltration, the kidneys are working harder than normal to compensate for early damage. This can precede a decline in eGFR, so if you have diabetes and a very high eGFR, your doctor may still monitor your kidney function closely and check for microalbuminuria.

In most other cases, an eGFR above 90 simply reflects healthy kidney function and does not require further investigation.

eGFR vs Creatinine — What's the Difference?

Creatinine and eGFR are closely related but measure different things.

| | Creatinine | eGFR | |---|---|---| | What it is | A waste product from muscle metabolism | An estimate of how well the kidneys filter blood | | Normal range | 0.7–1.3 mg/dL (men), 0.6–1.1 mg/dL (women) | ≥ 90 mL/min/1.73 m² | | Affected by muscle mass | Yes — muscular people may have higher creatinine without kidney disease | Yes — the formula partially accounts for this using age and sex | | Clinical use | Raw measurement from the blood sample | Calculated from creatinine, age, and sex to provide a functional assessment |

Creatinine alone can be misleading. A creatinine of 1.2 mg/dL might be perfectly normal for a muscular 30-year-old man but could represent significant kidney dysfunction in a 75-year-old woman with low muscle mass. eGFR helps standardize the interpretation by accounting for age and sex.

Limitations of eGFR

While eGFR is the standard tool for assessing kidney function, it has limitations:

• Muscle mass extremes — eGFR may overestimate kidney function in people with very low muscle mass (such as those with malnutrition, amputations, or muscle-wasting conditions) and underestimate function in bodybuilders or highly muscular individuals.
• Diet — consuming large amounts of cooked meat shortly before the blood draw can temporarily raise creatinine and lower the calculated eGFR.
• Medications — certain drugs, including trimethoprim and cimetidine, can raise serum creatinine without actually affecting kidney function by blocking creatinine secretion in the kidney tubules.
• Acute kidney injury — eGFR is designed to assess stable, chronic kidney function. During an acute kidney injury, creatinine levels are changing rapidly and the eGFR formula may not reflect real-time kidney function.
• Pregnancy — blood volume increases during pregnancy, which lowers creatinine concentrations and can make eGFR appear falsely elevated.

When eGFR results are uncertain or don't match the clinical picture, doctors may order a cystatin C-based eGFR, which uses a different protein not affected by muscle mass. Some labs now report both creatinine-based and cystatin C-based eGFR for greater accuracy.

When Dialysis Is Considered

Dialysis is typically considered when eGFR falls below 15 mL/min/1.73 m² (CKD Stage G5), though the decision depends on symptoms, not a strict number cutoff. Common symptoms at this stage include:

• Severe fatigue and weakness
• Nausea, vomiting, or loss of appetite
• Fluid retention causing swelling in the legs, ankles, or around the eyes
• Difficulty concentrating or mental confusion
• Shortness of breath from fluid buildup
• High potassium levels that don't respond to dietary changes or medication

Some patients begin dialysis when their eGFR is between 5 and 10, while others may start earlier if symptoms are significantly affecting quality of life. Kidney transplant is the other major option for Stage G5 CKD and, when available, generally provides better long-term outcomes than dialysis.

When to See a Doctor

Contact your doctor if:

• Your eGFR is below 60 on two or more tests taken at least three months apart.
• Your eGFR has dropped significantly from a previous result, even if it's still above 60 — a rapid decline in eGFR (more than 5 mL/min/1.73 m² per year) warrants investigation.
• You have protein or blood in your urine alongside a low eGFR.
• You have diabetes or high blood pressure and your eGFR is trending downward.
• You experience symptoms of advanced kidney disease — persistent fatigue, swelling, changes in urination patterns, or unexplained nausea.

Early detection of CKD allows for interventions that can slow progression. Blood pressure control, blood sugar management, dietary modifications, and avoiding nephrotoxic medications can significantly preserve remaining kidney function.

FAQ

What is a good eGFR number?

An eGFR of 90 or above is considered normal and indicates healthy kidney function. Values between 60 and 89 may be normal for older adults but should be evaluated in the context of your age, medical history, and whether there are other signs of kidney damage such as protein in the urine.

Can eGFR improve?

In some cases, yes. If a low eGFR is caused by a treatable condition — such as dehydration, a medication side effect, or uncontrolled blood pressure — addressing the underlying cause can improve kidney function. However, chronic kidney disease from long-standing diabetes or hypertension typically does not reverse, though its progression can be slowed with proper treatment.

How often should eGFR be tested?

For healthy adults, eGFR is typically checked as part of annual blood work. If you have CKD Stage G3 or higher, your doctor will likely order eGFR every 3 to 6 months. People with diabetes or hypertension should have their eGFR checked at least annually, or more frequently if kidney function is declining.

Does drinking water affect eGFR?

Drinking water does not directly improve your eGFR. However, dehydration can temporarily raise creatinine levels and lower your calculated eGFR, so being well-hydrated before your blood draw can help ensure an accurate result. Chronic overhydration does not boost kidney function.

Is eGFR the same as GFR?

Not exactly. GFR (Glomerular Filtration Rate) is the actual rate at which your kidneys filter blood, measured through specialized procedures involving injected tracers. eGFR (estimated GFR) is a calculated approximation based on your serum creatinine, age, and sex. For most clinical purposes, eGFR is accurate enough to guide diagnosis and treatment without the complexity of a measured GFR.

Track Your Kidney Health with healthbook.my

Monitoring your eGFR over time is one of the most important things you can do for your kidney health, especially if you have risk factors like diabetes or high blood pressure. With healthbook.my, you can upload your eGFR results and get instant AI-powered explanations of your kidney function — in plain language, with trends tracked automatically across multiple lab reports. Instead of comparing numbers across paper reports, see a clear picture of whether your kidney function is stable, improving, or declining, and know exactly what to discuss with your doctor.