eGFR Test: Understanding Your Estimated Kidney Function

What Is an eGFR Test?

eGFR stands for estimated glomerular filtration rate. It is a calculation, not a direct measurement, that estimates how much blood your kidneys filter each minute. The result reflects the combined work of the glomeruli, the tiny filters inside each kidney.

Labs calculate eGFR from your blood creatinine level along with your age and sex. Some formulas also factor in cystatin C, another blood protein. Because eGFR is an estimate, it is reported as a number and often categorized into stages rather than as a simple pass or fail.

eGFR is one of the most useful kidney markers because it can drop before you feel any symptoms. That early warning gives you and your clinician time to act, which is why eGFR is checked in routine blood work and whenever kidney health is a concern.

Why an eGFR Test Is Ordered

eGFR is ordered to:

• Screen for kidney problems during routine blood work
• Monitor a known kidney condition over time
• Watch for kidney side effects from medications
• Evaluate risk in people with diabetes or high blood pressure
• Follow up on an abnormal creatinine or urinalysis result

It is usually reported together with creatinine, BUN, electrolytes, and a urinalysis. Looking at these markers together shows whether a change is stable or getting worse.

What Normal and Low eGFR Levels Mean

eGFR is measured in milliliters per minute per 1.73 square meters (mL/min/1.73 m2). Reference values are usually framed as stages:

A single eGFR below 60 does not automatically mean chronic kidney disease. The label usually requires a reduced result lasting three months or longer, plus other findings. eGFR also tends to fall naturally with age, so a value in the 60s can be normal for an older adult. A steady decline over several tests is the pattern that matters most.

How to Order an eGFR Test and Where to Get Tested

You can order kidney function testing without a doctor's visit in most US states. Online lab-testing directories let you choose a metabolic panel, a kidney function panel, or cystatin C testing. After paying, you download a requisition and visit a CLIA-certified lab or one of our partner lab locations for a blood draw.

1. Choose a panel that reports eGFR, such as a basic or comprehensive metabolic panel.
2. Pay online and print your requisition.
3. Visit a nearby walk-in testing site.
4. View results in a secure portal, often within one to two business days.

Tell the lab about any medications, especially those that can affect the kidneys, and about your hydration level on the day of the draw.

How Much Does an eGFR Test Cost?

eGFR is usually not billed on its own. It is included with a basic metabolic panel, which commonly costs about $25 to $60, or a comprehensive metabolic panel, which usually runs $35 to $90. A cystatin C test added to the panel can raise the price. Insurance may cover testing when a clinician documents a medical reason.

Preparation and What to Expect

A metabolic panel that reports eGFR often asks for fasting. Stay hydrated unless your clinician tells you otherwise, since dehydration can lower eGFR temporarily. The blood draw takes only a few minutes.

Because eGFR is an estimate, a low result is usually confirmed with a repeat test and a urinalysis. Two or more reduced results over time give a much clearer picture than one value.

Because eGFR is an estimate, it is usually confirmed before it changes your care. A clinician may repeat the test, add a urinalysis to check for protein, and sometimes order a cystatin C based estimate, which can be more accurate for people with unusual muscle mass. Two reduced results at least three months apart carry more weight than one.

Day-to-day habits support kidney health: keep blood pressure and blood sugar in a healthy range, stay hydrated, and review medications that can affect the kidneys with your clinician or pharmacist. If eGFR is falling quickly, that pattern deserves prompt attention.