The RenalTracker Team
July 28, 2020

eGFR Test for Kidney Function

gfrdial heroshot

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. 

Your doctor gets your eGFR by calculating the creatinine level present in your blood. eGFR also determines your kidney disease stage. A low eGFR number could indicate your kidneys are not functioning properly.

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

How is the eGFR Test Done?

CKD Blood Test

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. 

After determining your blood creatinine level, your doctor will then use a formula to calculate your eGFR together with other factors including your age, gender, race and ethnicity, height, and body weight.

What Does the Test Result Indicate?

CKD Blood Tests

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.

AGE (years)

eGFR VALUE

20 to 29

116

30 to 39

107

40 to 49

99

50 to 59

93

60 to 69

85

70+

75

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.

Kidney damage may still be present even when a person has an eGFR higher than 90 mL/min/1.73m2. An increase in albumin (protein in urine) is another sign of kidney damage

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:

CKD Stage

Description

eGFR Value
(mL/min/1.73m2)

Other

Findings

1

Normal or minimal kidney damage

90+

Protein or albumin level in urine may be high (urinalysis is needed to measure this)

2

Mild decrease in filtration rate

60 to 89

Protein or albumin level in urine may be high (urinalysis is needed to measure this)

3

Moderate decrease in filtration rate

30 to 59

Cell

4

Severe decrease in filtration rate

15 to 29

Cell

5

Kidney failure (immediate kidney transplant or dialysis is required)

Below 15

Cell

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.

Early detection is key in managing your condition. With immediate diagnosis you get to receive early treatment, prevent the disease from worsening, and keep your kidneys working for many years.

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

  • Control your blood pressure. People with CKD usually need to keep their blood pressure at 130/80 mm Hg or lower. It would be best to ask your doctor about the right blood pressure you need to maintain.
  • Address other health conditions. Diabetes and high cholesterol anemia are the leading causes of kidney disease. Diabetes can injure the small blood vessels which eventually impairs the kidneys’ blood-filtering capacity. Too much cholesterol can clog the renal arteries and prevent normal blood flow to the kidneys, resulting in loss of kidney function. Treating these diseases along with following a healthy lifestyle can prevent CKD from worsening.
  • Shift to a healthy lifestyle. Keeping a healthy lifestyle plays a significant role in managing CKD. Exercise regularly to maintain a healthy body weight. Avoid smoking and drinking alcoholic beverages as these habits are hard on your kidneys.
  • Switch to a kidney-friendly diet. Being conscious of your eating and drinking habits remains to be the best way to preserve your kidney health. Remember to limit your sodium, phosphorus, potassium, and protein intake to avoid straining your kidneys. 

Seek the help of a renal dietitian in creating a renal-friendly meal plan specific to your CKD condition.


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.