Glomerular filtration rate (GFR) is a measure of how well the kidneys filter blood. It is used to assess kidney function and diagnose conditions such as chronic kidney disease. GFR is typically calculated using a formula that takes into account factors such as age, gender, race, and levels of creatinine in the blood. A normal GFR is usually around 90-120 mL/min/1.73m2, and a GFR below 60 may indicate kidney dysfunction. Monitoring GFR is important for managing and treating kidney disease and other related conditions.