Serum Creatinine to Albumin Ratio (Creatinine-Albumin Ratio, CAR)

What Does This Test Measure?

Creatinine is a byproduct of muscle metabolism that the kidneys filter out of your blood. Albumin is a protein that helps maintain fluid balance in your body. The CAR test compares these two substances to evaluate how well your kidneys are working and whether protein is being lost through urine.

Why Might Your Doctor Order This Test?

Your doctor may recommend this test if you have symptoms like swelling, frequent urination, or unexplained weight changes. It can also be used to monitor kidney disease, chronic conditions like diabetes or heart failure, or to check for conditions like nephrotic syndrome, where large amounts of protein leak into urine.

How Is This Test Performed?

A small blood sample is drawn from a vein, usually in your arm. The blood is then sent to a lab where it is analyzed to measure both creatinine and albumin levels. The ratio is calculated automatically by the lab.

What Are Common Results and Their Meanings?

A higher-than-expected ratio may indicate kidney problems, such as reduced kidney function or protein loss in urine. A lower ratio might suggest conditions affecting protein levels in the blood, though this is less common. Your results will be interpreted by your healthcare provider in the context of your overall health and medical history.