We used to focus on a patient’s blood creatinine level to help determine how much function you have remaining before you need to start dialysis. Now we focus on the glomerular filtration rate or GFR. Once we have the GFR, we convert that number to a stage (1 to 5), with Stage 1 chronic kidney disease (CKD) being the best stage and stage 5 CKD being the worst stage. Why use GFR, which by the way happens to be a calculated number, instead of serum creatinine? GFR is a better marker to determine your true or real kidney function. That helps us risk stratify or determine how much time your kidneys have left. We can do many other things with that number. For example, focusing on prevention, we can start certain medications at certain GFRs that help keep you off dialysis, are good for the heart, keep you out of the hospital, and keep you living longer. The GFR has become an essential tool in the management of kidney patients. Nephrologists and patients should work together, using shared decision making, to work to prevent the progression of chronic kidney disease.