Creatinine
Test Overview
The Creatinine Test measures the level of creatinine in the blood or urine, a waste product generated by muscle metabolism and excreted by the kidneys. It is a key indicator of kidney function, as elevated creatinine levels may suggest impaired kidney function or disease.
Test Uses
- Evaluates kidney function and detects kidney disease.
- Monitors chronic kidney disease (CKD) or acute kidney injury.
- Assesses muscle metabolism and overall creatinine clearance when combined with a urine creatinine test.
- Used in calculating the estimated glomerular filtration rate (eGFR) to assess kidney function.
Creatinine Test Results & Ranges
| Test Component: | Normal Range: | Abnormal Levels Indicate: |
|---|---|---|
| Serum Creatinine (Blood Test) | Men: 0.7 – 1.3 mg/dL Women: 0.6 – 1.1 mg/dL |
High: Kidney disease, dehydration, muscle breakdown Low: Low muscle mass, liver disease, malnutrition |
| Urine Creatinine (24-Hour Collection) | 500 – 2000 mg/day (Men) 400 – 1500 mg/day (Women) |
Low: Kidney dysfunction, low muscle mass High: Dehydration, high protein intake, muscle breakdown |
| Creatinine Clearance (eGFR Calculation) | >90 mL/min (Normal kidney function) | 60 – 89 mL/min: Mild kidney damage 30 – 59 mL/min: Moderate kidney disease <30 mL/min: Severe kidney impairment |
Interpreting Abnormal Creatinine Levels:
-
High Creatinine Levels:
- Kidney disease or impaired kidney function.
- Dehydration (causes temporary elevation).
- High muscle mass or recent intense exercise.
- Excessive protein intake or creatine supplementation.
-
Low Creatinine Levels:
- Muscle disorders or reduced muscle mass (e.g., aging, malnutrition).
- Liver disease affecting protein metabolism.
- Pregnancy (can lower creatinine due to increased kidney filtration rate).
Expected Turnaround Time
- Results Available: Typically within 24–48 hours.
Specimen Requirements
- Sample Type: Blood (serum) or urine (random or 24-hour collection).
- Container:
- Blood Sample: Serum separator tube (SST, gold-top tube).
- Urine Sample: Sterile urine collection cup or 24-hour urine container.
Collection Instructions
- For a blood test: No special preparation is required, but staying hydrated can help ensure accurate results.
- For a 24-hour urine test:
- Discard the first morning urine, then collect all urine for the next 24 hours.
- Store the urine container in a cool place or refrigerator during collection.
- Return the full 24-hour sample to the lab as instructed.
Test Details
Clinical Use: Primary test for kidney function evaluation. Monitors chronic kidney disease (CKD), diabetes, and high blood pressure effects on the kidneys. Used in creatinine clearance and eGFR calculations to determine kidney filtration efficiency.
Limitations: Creatinine levels can be influenced by diet, hydration, and muscle mass. High-protein diets or intense exercise can temporarily elevate creatinine levels. Low levels may not always indicate disease but could reflect low muscle mass.
The Creatinine Test is a fundamental measure of kidney function and muscle metabolism, providing crucial insight into renal health and overall well-being.