Creatinine Test
Also known as: Serum Creatinine, Blood Creatinine
What is Creatinine?
Creatinine is a waste product produced by muscles during normal activity. Healthy kidneys filter creatinine out of the blood and excrete it in urine.[MedlinePlus (NIH)]
What This Test Measures
This test measures the level of creatinine in your blood. Since creatinine is removed by the kidneys at a fairly constant rate, blood levels reflect how well your kidneys are working.[Mayo Clinic]
Why It's Important
Creatinine levels help assess kidney function. Rising creatinine levels may indicate that the kidneys are not filtering blood effectively.[MedlinePlus (NIH)]
Early detection of kidney problems allows for treatment that can slow or prevent further kidney damage.[Cleveland Clinic]
Who Should Get This Test?
Creatinine testing is recommended for people at risk of kidney disease:
Risk Factors
- People with diabetes (leading cause of kidney disease)
- Those with high blood pressure
- People with family history of kidney disease
- Adults over 60
- People with heart disease
- Those who are obese
- Smokers
- People taking medications that can affect kidneys (NSAIDs, certain antibiotics)
- Those with autoimmune conditions (lupus, etc.)
- People with recurrent kidney infections
- Those of African American, Hispanic, or Native American descent
- People with previous acute kidney injury
Screening Schedule
Annually for people with diabetes or high blood pressure; as recommended for others with risk factors
What Happens During the Test
A healthcare provider draws blood from a vein in your arm. The sample is sent to a laboratory where creatinine levels are measured. A urine creatinine test may also be ordered.
Duration
5 minutes or less
Discomfort Level
Minimal - brief pinch when needle is inserted
Risks & Side Effects
This is a routine blood test with very low risks.
- •Slight pain or bruising at needle site
- •Brief lightheadedness (rare)
- •Small risk of infection (very rare)
Normal Range
For men: 0.7 to 1.3 mg/dL. For women: 0.6 to 1.1 mg/dL.
Note: Normal ranges vary based on age, muscle mass, and the laboratory. Athletes may have higher normal levels.
Source: MedlinePlus (NIH)Unit Conversion
Convert between mg/dL and µmol/L
| mg/dL | µmol/L |
|---|---|
| 0.6 | 53 |
| 0.8 | 71 |
| 1 | 88 |
| 1.2 | 106 |
| 1.5 | 133 |
| 2 | 177 |
High Values
High creatinine usually indicates impaired kidney function. Causes include chronic kidney disease, kidney infection, dehydration, and certain medications. It may also be higher in people with more muscle mass.[Mayo Clinic]
Low Values
Low creatinine is less common and may be associated with decreased muscle mass, severe liver disease, or a diet very low in protein.[Cleveland Clinic]
Test Limitations & Accuracy
Several factors can affect creatinine test accuracy:
- ⚠Muscle mass affects creatinine production (athletes may have higher levels)
- ⚠Diet high in meat can temporarily raise creatinine
- ⚠Creatine supplements can increase creatinine levels
- ⚠Certain medications affect creatinine (trimethoprim, cimetidine)
- ⚠Dehydration can raise creatinine levels
- ⚠Age affects normal ranges (decreases with age-related muscle loss)
- ⚠Intense exercise before the test may elevate levels
- ⚠Creatinine can be normal early in kidney disease
Alternative & Complementary Tests
Other tests used to assess kidney function:
Calculated from creatinine; better overall kidney function estimate
Alternative marker less affected by muscle mass
Another waste product filtered by kidneys
Detects kidney damage early
24-hour urine test for precise GFR measurement
To visualize kidney structure and size
Frequently Asked Questions
How can I lower my creatinine levels?
To support kidney health: stay hydrated, reduce protein intake if advised by your doctor, avoid NSAIDs and other kidney-stressing drugs, manage blood pressure and blood sugar, exercise regularly, and avoid creatine supplements.
Source: Cleveland ClinicWhat foods should I avoid with high creatinine?
If you have kidney problems, you may need to limit high-protein foods (red meat, poultry, fish), sodium, potassium (bananas, potatoes), and phosphorus (dairy, nuts). Work with a dietitian for personalized guidance.
Source: MedlinePlus (NIH)Does high creatinine mean kidney failure?
Not necessarily. High creatinine indicates reduced kidney function, but it doesn't always mean kidney failure. Temporary causes include dehydration and certain medications. Persistent elevation needs evaluation.
Source: Mayo ClinicWhat is eGFR and how does it relate to creatinine?
eGFR (estimated Glomerular Filtration Rate) is calculated from creatinine levels, age, sex, and race. It estimates how well your kidneys filter blood. An eGFR below 60 for 3+ months may indicate chronic kidney disease.
Source: MedlinePlus (NIH)References
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Medical Disclaimer
This information is for educational purposes only and is not intended as medical advice. Always consult with a qualified healthcare provider for interpretation of test results and medical decisions.
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