eGFR Test for Kidney Function

Getting your estimated glomerular filtration rate (eGFR) is the simplest way for your doctor to find out how well your kidneys are working. This number represents the rate at which your kidneys filter blood. 

Read on to find out how your doctor uses your kidneys’ filtration rate to evaluate your kidney health.

How is the eGFR Test Done?

Prior to your test, your doctor may advise you to stop taking certain medicines, vitamins, or supplements temporarily.

A lab specialist will draw a blood sample from your vein, then the sample is sent to the lab to measure its creatinine content. 

What Does the Test Result Indicate?

eGFR values are reported as “mL/min/1.73m2” (read as milliliters per minute per 1.73m2). According to the National Kidney Foundation, a ‘normal’ eGFR result is anywhere between 90 and 120 mL/min/1.73m2. 

However, older adults are expected to have lower values than normal eGFR levels as the kidneys’ filtering capacity decreases with age. Check out the table below for the average eGFR based on age range.

Also, normal value ranges can vary from one lab to another. Before getting tested, make sure to know the standard range for your lab and feel free to ask your nephrologist to explain your results to you.

An eGFR lower than 60 mL/min/1.73m2 may indicate that the kidneys have some damage. You may need to undergo another round of tests to see if the same result persists. In many cases, CKD is diagnosed when a person’s test results consistently show an eGFR lower than 60 mL/min/1.73m2 for 3 months or so.

To rule out other possible factors, doctors take into consideration the patient’s medical history and existing conditions when interpreting their test results.

Below is a table that shows eGFR values and the corresponding kidney disease stage:

So My Results Suggest I May Have CKD. What’s Next?

Your nephrologist will identify the root cause of your kidney disease (the common causes of CKD are diabetes and high blood pressure). This is necessary in creating a treatment plant based on your unique condition. Your doctor will also regularly conduct tests to closely monitor your kidney function. Talk with your doctor to know how often you should get the tested.

You also need to have your albumin level checked. If you have CKD, albumin checks will be a part of your routine medical exam as a way of monitoring the progression of your disease. This is done through a dipstick test wherein a nurse or medical technician will place a chemically-treated strip into your urine sample. If the strip changes color, it means albumin is present in your urine.

High albumin levels indicate that a person’s kidney disease is likely to progress to kidney failure. A normal albumin amount in urine is less than 30 mg/g. Anything above 30 means you have CKD (even if your eGFR is above 60). 

To lower your albumin, you need to maintain a healthy body weight, avoid foods that are high in sodium/salt, and eat the right amount of protein. Your nephrologist may also prescribe you with medications to lower your blood pressure.

Other tests you might undergo to further assess your kidney health include:

• Ultrasound or CT scan - Imaging tests are used to get a picture of your kidneys and urinary tract and check for abnormalities.
• Kidney biopsy - This test helps determine the extent of damage to your kidneys. In a kidney biopsy, a physician takes a sample of your kidney tissue and examines it under a microscope.

Below are additional reminders when looking at your eGFR:

1. It is only an estimate of how well kidneys are functioning. It can be prone to error. It is possible for eGFR values to be inaccurate in amputees, obese and malnourished individuals, as well as people with more or less muscles.
2. Certain racial groups may not fit the eGFR equations well. This is because these equations were derived from datasets from white and black US citizens.
3. Laboratories use different methods to measure creatinine, so values can vary from one laboratory to another. Laboratories may also use different formulas in calculating eGFR.
4. Creatinine levels should be stable, otherwise they are invalid. eGFR values presume that blood creatinine level is steady for days, weeks, or months. eGFR calculations are not valid in people on dialysis or those with acute kidney injury.

What Should I Do if I Have CKD?

If you have chronic kidney disease, your kidneys are not able to filter blood, produce vital hormones, and keep your protein, sodium, and calcium levels as stable as before.

Follow your nephrologist’s advice and make sure to do the following:

To improve your kidney lab test results, learn which foods to eat on a renal diet. Scroll down to download your free Kidney-friendly Food list eBook.