Your kidney numbers include 2 tests: ACR (Albumin to Creatinine Ratio) and GFR (glomerular filtration rate). GFR is a measure of kidney function and is performed through a blood test. Your GFR will determine what stage of kidney disease you have – there are 5 stages. Know your stage.ACR is a urine test to see how much albumin (a type of protein) is in your urine. Too much albumin in your urine is an early sign of kidney damage.