Creatinine and Creatinine Clearance Blood Tests
Understanding an Abnormal Creatinine Test Result
A low GFR or creatinine clearance demonstrates kidney disease. The decline in kidney function can be either acute (sudden, often reversible) or chronic (long-term and irreversible). Repeated GFR or creatinine clearance measurements over time can identify kidney disease as acute or chronic.
Kidney function and creatinine clearance naturally decline with age. Fortunately, the kidneys have a huge reserve capacity. Most people can lose well over half their renal function without symptoms or significant problems.
Doctors determine the severity of chronic kidney disease with a staging system that uses GFR:
Stage 1: GFR 90 or greater (normal kidney function)
Stage 2: GFR 60-90 (mild decline in kidney function)
Stage 3: GFR 30-59 (moderate decline in kidney function)
Stage 4: GFR 15-29 (severe decline in kidney function)
Stage 5: GFR less than 15 (kidney failure, usually requiring dialysis)
People over age 60 may have an apparently normal creatinine blood level, but still have a low GFR and creatinine clearance. The 24-hour urine collection method, or one of the GFR estimation formulas, can more accurately identify the decline in kidney function.
What to Do About a Low Creatinine Clearance
If you have a low GFR or creatinine clearance, your doctor will design an action plan with you to address the problem.
The main causes of chronic kidney disease are high blood pressure and diabetes. If you have these conditions, the first step is to get them under control with improved diet, exercise, and medications. If these conditions are not present, further testing may be needed to identify the cause of kidney disease.
Periodically checking the GFR or creatinine clearance allows you and your doctor to follow any decline in kidney function over time. Your doctor may need to make changes in your medications to adjust for any decline in renal function.
Most people do not need dialysis until GFR and creatinine clearance fall very low. However, because kidney function naturally declines with age, it's important to take action early to preserve all the kidney function you can.