An EGFR test is performed when a person's kidney function is suspected to be impaired or to investigate the condition of kidney disorders. eGFR is a key parameter used in determining kidney damage. In some cases, assessment of kidney function is specifically recommended. Situations where an EGFR test is primarily recommended include:

Pregnancy
Heart conditions
Diabetes
Genetic predisposition
Recurrent urinary tract infections
Urinary tract obstructions
High blood pressure
Obesity
Tobacco use

In cases of damage to the kidneys, a part of the urinary system, or the presence of a different kidney disease, the glomeruli filter less blood. Creatinine is produced from dietary animal protein and the metabolism of phosphocreatine in skeletal muscle, therefore its production in the body is proportional to muscle mass. Accordingly, it is affected by age, sex, and body mass. Insufficient blood filtration leads to the accumulation of dangerous toxins in the body. Impaired kidney function results in an increase of breakdown products such as urea and creatinine in the blood. The elevated urea and creatinine levels resulting from decreased kidney function may not show significant clinical symptoms in early stages. Over time, the patient may experience weakness, joint pain, decreased urine output, and itching.