eGFR

Each kidney holds about a million tiny filters called nephrons. As blood flows through them, water and waste get pushed out toward your urine while proteins and blood cells stay behind. The combined speed of all that filtering is your filtration rate.

Measuring that speed directly is impractical, so labs estimate it. Creatinine, a steady waste product from your muscles, builds up when filtering slows down. A formula combines your creatinine with your age and sex, scaled to a standard body size, to land on your eGFR.

Higher is the goal here. A strong number means your kidneys are keeping pace with the waste your body makes, and a lot of what moves it is in your hands. As eGFR drops, waste and fluid linger, which can touch your blood pressure, bones, blood counts, and heart.

An eGFR below 60 that lasts three months or more defines chronic kidney disease, or CKD. Under 15 means kidney failure. The good news is that decline is usually slow and shaped by things you can change, so spotting a downward trend early helps protect the function you still have. Read it as one clue alongside a urine albumin test and the rest of your panel, with your clinician, not a diagnosis on its own.