To create urine, your kidneys filter your blood by eliminating waste and excess water. The glomerular filtration rate (GFR), or kidney filtration rate, indicates how efficiently the kidneys filter. When chronic kidney disease (CKD) is detected early, an estimated 37 million individuals in the United States can take the actions necessary to safeguard their kidney function.

The glomerular filtration rate (GFR) is a test that determines how well the kidneys function. It calculates the amount of blood that flows through the glomeruli each minute. The tiny filters in the kidneys that filter waste from the blood are known as glomeruli.

What does it do?

A glomerular filtration rate (GFR) test measures how well your kidneys filter blood. Glomeruli are small filters found in your kidneys. These filters assist in the removal of waste and excess fluid from the bloodstream. A GFR test calculates the amount of blood that flows through these filters each minute.

A GFR may be tested directly, but it’s an intricate procedure that requires expert providers. As a result, an estimated GFR, or eGFR, is frequently used to estimate GFR. Your physician will utilize a GFR calculator to come up with an estimate. A GFR calculator is a mathematical formula that calculates the filtration rate. It is accomplished by comparing the results of a blood test that detects creatinine, a waste product filtered by the kidneys, with other data about you. 

Some or all of the following is included in this data:

Age 

Weight 

Height 

Gender 

Race

Why is GFR Testing done?

A GFR test is used to identify kidney disease early on when it is still curable. GFR can also be used to track patients with chronic kidney disease (CKD) or other kidney-damaging diseases. Diabetes and excessive blood pressure are two of them.

Early-stage kidney disease typically has no symptoms, but if you are at a higher risk of developing kidney disease, your doctor may prescribe an eGFR test. The following are some of the risk factors for CKD:

• Diabetic or hypertensive disorders
• Blood pressure that is too high
• Being overweight
• Kidney failure in the family

Symptoms of late-stage CKD do exist. If you experience any of the following symptoms, you may require an eGFR test:

• Urinating more frequently or less frequently than normal
• Itching
• Fatigued.
• Swelling in your arms, legs, or feet is a common symptom.
• Muscle spasms
• Vomiting and nausea
• Appetite loss.

Risks

Having a blood test carries relatively little risk. You may have little discomfort or bruising where the needle was inserted, but most symptoms fade rapidly.

Preparation

Before the test, you may need to fast (not eat or drink) or avoid specific meals for a few hours. If there are any particular instructions to follow, your health care practitioner will inform you.

Process: What can you expect?

A tiny needle will be used to draw a blood sample from a vein in your arm by a health care expert. A tiny amount of blood will be collected into a test tube or vial once the needle is placed. When the needle goes in or out, it may hurt a bit. It generally takes less than five minutes to do this task.

Following the examination, after the blood is collected for the test, there are usually no limitations.

Results

A GFR of 60 or greater is considered normal.

A GFR of less than 60 indicates renal disease.

A GFR of 15 or below might indicate renal failure.

How to calculate GFR?

Your GFR indicates how well your kidneys are working. It’s calculated as the total of all of your nephrons’ filtration rates (filtering units making up the kidneys). 

The equation GFR = 140 – [your age] may be used to calculate an approximation of your GFR’s standard value. 

For example, if you’re a fit, healthy 30-year-old, your GFR should be about 110 milliliters per minute.

There are a variety of formulas that may be used to determine the GFR. However, the Cockcroft & Gault and MDRD formulas are the most often utilized.

1. The Cockcroft-Gault equation considers age, gender, and muscle mass (multiplied by 1.23 for males to account for a more significant percentage of body weight): Creatinine clearance = [140 – age (years)] x LBW (kg) x 1.23 (if male) (mls/min) / Serum creatinine (umol/L)
2. MDRD is a medical term that refers to (modification of diet in renal disease). To make calculating the GFR easier, the MDRD equation has been simplified: 186.3 x Serum Creatinine (exp[-1.154]) x Age (exp[-0.203]) x (0.742 if female) x GFR (mL/min per 1.73 m2;1.21) = 186.3 x Serum Creatinine (exp[-1.154]) x Age (exp[-0.203]) x (0.742 if female) x (1.21 if african american). 

To use this method to estimate your GFR, you’ll need to know your age, gender, race, and creatinine levels from blood tests.

What are normal GFR Levels?

The usual range for GFR is 90 or greater. However, this varies by age. 

Because kidney damage is limited at this stage, stage 1 CKD has an eGFR of 90 or greater. As a result, your doctor may order further tests to confirm a CKD diagnosis. You may be at risk for more significant kidney injury if your eGFR falls below 90. If you have any doubts about whether your GFR levels are typical for you, speak with your doctor.

Given below is the table of GFR levels for stagewise Kidney damage:

Stage

Description

GFR

1

Kidney damage with normal or high GFR

90 or above

2

Kidney damage with mildly low GFR

60–89

3

Kidney damage with moderately low GFR

30–59

4

Kidney damage with severely low GFR

15–29

5

Kidney failure

Below 15

Can I have kidney disease even if my GFR is normal?

Yes, even if you have symptoms of kidney disease, such as protein in your urine (pee) or physical damage to your kidneys, your eGFR may still be within acceptable limits.

If you have protein in your urine, your doctor will examine you again to ensure that it is not the result of something else, such as dehydration.

Take the following actions to keep your kidneys as healthy as possible, regardless of your eGFR:

• Maintain a healthy blood pressure (for most people, less than 120/80).
• If you have diabetes, keep your blood sugar under control.
• Maintain a healthful low-salt, low-saturated-fat diet.
• Most days of the week, do something energetic for at least 30 minutes, like walking or bicycling.
• Maintain a healthy weight