Creatinine
A blood test that measures creatinine levels to evaluate how well the kidneys are filtering waste from the blood.
Last medically reviewed: April 10, 2026 | Reviewed by LabResult.MD Editorial Team
What is Creatinine?
Creatinine is a waste product that is produced when muscles break down a compound called creatine during normal muscle activity. The kidneys filter creatinine out of the blood, and it is then excreted in the urine.
Because creatinine is produced at a fairly constant rate and is filtered almost entirely by the kidneys, it is one of the most reliable markers for kidney function. A creatinine blood test is commonly included in both the Basic Metabolic Panel (BMP) and the Comprehensive Metabolic Panel (CMP).
Why Is It Tested?
A healthcare provider may order a creatinine test to:
- Evaluate kidney function as part of a routine checkup
- Monitor known kidney disease or chronic kidney disease (CKD)
- Assess kidney function before or after starting medications that can affect the kidneys
- Investigate symptoms such as swelling, fatigue, changes in urination, or high blood pressure
- Calculate the estimated glomerular filtration rate (eGFR), which provides a more precise measure of kidney function
- Monitor patients with diabetes or high blood pressure, which are risk factors for kidney disease
Normal Reference Ranges
Reference ranges may vary by laboratory, testing method, age, and other factors. Always use the ranges provided on your lab report.
| Population | Normal Range (mg/dL) |
|---|---|
| Adult Men | 0.74 – 1.35 mg/dL |
| Adult Women | 0.59 – 1.04 mg/dL |
| Adolescents | 0.5 – 1.0 mg/dL |
| Children (3–12 years) | 0.3 – 0.7 mg/dL |
What Does a High Creatinine Level Mean?
High creatinine levels usually indicate that the kidneys are not filtering waste as effectively as they should. Possible causes include:
- Chronic kidney disease (CKD) or acute kidney injury
- Dehydration (which temporarily reduces kidney filtration)
- High-protein diet or excessive creatine supplementation
- Intense exercise or high muscle mass (which produces more creatinine)
- Medications that affect kidney function (NSAIDs, certain antibiotics, ACE inhibitors)
- Urinary tract obstruction (kidney stones, enlarged prostate)
- Conditions that reduce blood flow to the kidneys (heart failure, shock)
A single elevated creatinine result does not necessarily mean kidney disease. A healthcare provider will consider trends over time and other test results to make a diagnosis.
What Does a Low Creatinine Level Mean?
Low creatinine levels are less common and usually not a primary concern, but they may indicate:
- Low muscle mass (due to aging, malnutrition, or muscle-wasting diseases)
- Severe liver disease (the liver produces creatine, the precursor to creatinine)
- Excessive fluid intake (diluting blood creatinine levels)
- Pregnancy (blood volume increases, diluting creatinine)
Low creatinine on its own is typically not alarming, but a healthcare provider may investigate further if combined with other abnormal results.
Common Next Steps
Depending on the result, a healthcare provider may recommend:
- Calculating the eGFR (estimated glomerular filtration rate) for a more precise kidney function assessment
- BUN (blood urea nitrogen) test to further evaluate kidney function
- Urinalysis to check for protein, blood, or other abnormalities in the urine
- Kidney imaging (ultrasound or CT scan) to look for structural problems
- Repeat testing in a few weeks to monitor trends
- Dietary adjustments and medication review if kidney function is declining
Frequently Asked Questions
What is a normal creatinine level?
Normal creatinine levels are typically 0.7–1.3 mg/dL for men and 0.6–1.1 mg/dL for women. Levels can vary based on age, muscle mass, diet, and the laboratory performing the test.
Does high creatinine always mean kidney disease?
Not necessarily. Creatinine can be temporarily elevated by dehydration, intense exercise, high-protein meals, or certain medications. However, persistently elevated creatinine warrants further evaluation. The National Kidney Foundation recommends calculating GFR for a more accurate assessment.
What is the difference between creatinine and GFR?
Creatinine is a waste product measured in the blood. GFR (glomerular filtration rate) is calculated from creatinine levels along with age, sex, and body size to estimate how well the kidneys are filtering. A GFR below 60 mL/min for 3 or more months indicates chronic kidney disease.
Related Tests and Biomarkers
Sources
- National Kidney Foundation. Estimated Glomerular Filtration Rate (eGFR)
- MedlinePlus. Creatinine Test. U.S. National Library of Medicine
- KDIGO Clinical Practice Guidelines for Chronic Kidney Disease (2024)
Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice. Reference ranges vary by laboratory. Always discuss your results with a qualified healthcare provider.