# GFR Calculator

Using a GFR calculator can help to assess kidney function and identify potential issues early on, which can allow for timely interventions to prevent or slow the progression of kidney disease.

### What is the Glomerular Filtration Rate (GFR)?

The glomerular filtration rate (GFR) is a test used to assess how well the kidneys are performing. It measures how much blood passes through the glomeruli (tiny kidney filters), i.e. kidneys’ ability to filter and excrete all metabolic waste products from the body. GFR is probably the best indicator of renal function and functional mass assessment. The estimates are used to detect the stage of CKD, assess its severity and monitor progress. When a clear picture of the patients’ renal condition is obtained, treatment methods can be decided. The earlier kidney disease is detected, the better the chances are of slowing down its progression.

## How is GFR estimated?

The calculation of glomerular filtration rate is done through various methods such as:

• measurement of creatinine in plasma,
• determination of creatinine clearance after 24-hour urine collection and appropriate calculations, and
• lmost accurately, by radionucleotide methods

In everyday practice, the level of GFR can also be estimated by equations, taking into account the level of creatinine in blood (SCr) and variables like age, gender, body size and ethnicity.

One of the earliest GFR calculations is the Cockcroft-Gault creatinine clearance formula, which accounts for age, sex and muscle mass.

* If female, multiply the result by 0.85

However, more recent studies have shown that the Cockcroft-Gault can overestimate kidney function, which increases a risk of higher drug dosing recommendations.

Nowadays, the most widely-used equation in adults is the one proposed by the Modification of Diet in Renal Disease (MDRD) Study:

GFR(mL/min/1.73m2)=186×(SCr)−1.154×(age)−0.203×(0.742 if female)×(1.212 if African/American Black).

### What is a normal GFR number?

For adults, the normal GFR number is above 90. However, with age GFR declines even in people not suffering from kidney disease.

Age (years) Average estimated GFR
20 – 29 116
30 – 39 107
40 – 49 99
50 – 59 93
60 – 69 85
70+ 75

### Stages of chronic kidney disease, based on estimated GFR

Stage GFR Kidney Function
Stage 1 90 and higher Kidney damage with normal kidney function View more
Stage 2 60 to 89 Kidney damage with mild loss of kidney function View more
Stage 3 30 to 59 Kidney damage with moderate decrease in kidney function View more
Stage 4 15 to 29 Kidney damage with severe reduction of kidney function View more
Stage 5 Less than 15 or dialysis End-stage renal failure View more