What it is: A creatinine test measures the level of creatinine, a waste product from normal muscle breakdown, in the blood as a marker of kidney function.
Why it's ordered: Ordered to evaluate kidney function, often alongside BUN, as part of routine metabolic panels or when kidney disease is suspected based on symptoms or risk factors like diabetes or high blood pressure.
What it detects: Creatinine is normally filtered out by the kidneys at a steady rate; when kidney filtration declines, creatinine builds up in the blood. It's used to calculate the estimated glomerular filtration rate (eGFR), a more precise measure of kidney function.
Collection & prep: A standard blood draw from a vein in the arm. No special preparation is typically required.
Results:
High – suggests reduced kidney filtration; typical adult ranges are roughly 0.6–1.1 mg/dL (women) and 0.7–1.3 mg/dL (men)
eGFR below 60 for three months or more indicates chronic kidney disease; below 15 indicates kidney failure
Possible complications of reduced kidney function: Because creatinine is affected by muscle mass, age, and other non-kidney factors, providers typically rely on eGFR rather than creatinine alone, and declining kidney function is monitored over time alongside symptoms and other kidney markers.
Statements made in the Clinical Manual have not been evaluated by the FDA. The products mentioned are not intended to diagnose, treat, cure or prevent any disease.
