Kidney Function Tests: Creatinine, eGFR and Urine Protein

Kidney function is checked with inexpensive blood and urine tests. The two that matter most are creatinine (converted into an eGFR) and the urine albumin test for protein. Creatinine is a waste product made by muscle and cleared by the kidneys. eGFR is an estimate of filtering rate calculated from creatinine. Urea is a second waste marker. Urine albumin is the earliest sign of kidney damage. A single abnormal result does not confirm disease. Dehydration, diet, recent exercise and some medicines can nudge results up or down. The trend over time is what matters. Annual testing is advisable for anyone with diabetes, high blood pressure, a family history of kidney disease, or age over 60 — regardless of symptoms.