Serum Creatinine (Creatinine Level)
This test measures the amount of creatinine, a waste product from muscle metabolism, in your blood serum. It helps assess how well your kidneys are filtering blood.
["A creatinine test helps check kidney function by measuring waste removal efficiency."]
Key facts at a glance
- LOINC
- 109135-4
- Short code
- COLDAG
- Synonyms
- CA Msmt Ser
- Category
- chemistry
- Sample
- serum
- Container
- Red-top (no anticoagulant) serum tube; alternatively SST (serum separator tube). Sample must be transported and maintained at 37°C until serum is separated.
- Units
- N/A
- Ref low
- 0
- Ref high
- 1
- Critical range
- — – 1000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Agglutination assay; cold agglutinins are detected by titration of serum at 4°C (refrigerated temperature) with type O red blood cells, often confirmed by reactivity at 30°C and 37°C
- CPT
- 86156
- SNOMED
- 31307-2
- Specimen volume
- 2–5 mL of whole blood to yield at least 1–2 mL of serum
- Stability
- Serum should be separated at 37°C within 1–2 hours of collection. Stable at 2–8°C for 7 days if refrigerated; for prolonged storage, freeze at -20°C or below. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–72 hours
- Order
- routine
A creatinine test matters because it gives your care team a simple, reliable way to check how well your kidneys are filtering waste from your blood. Detecting kidney problems early allows treatment steps that can help slow or prevent further damage and protect your long-term health.
Your kidneys normally filter waste products like creatinine from your blood. High levels can signal kidney problems, while low levels may indicate dehydration or muscle breakdown. This test is often used alongside other kidney function tests to diagnose or monitor conditions like chronic kidney disease.
Before the test, you can usually eat and drink normally unless your doctor tells you otherwise. Let your care team know about all medicines and supplements you take, since some drugs can affect creatinine levels, and you may be asked to avoid strenuous exercise right before your blood is drawn.
No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a broader kidney function panel. Drink plenty of water the day before to ensure accurate results.
High creatinine levels are often caused by dehydration, chronic kidney disease, kidney infections, or blocked urine flow, as well as certain medicines such as NSAIDs and some blood pressure drugs. Eating a large amount of cooked meat or doing intense exercise shortly before testing can also raise levels temporarily, while low levels may reflect reduced muscle mass.
High creatinine levels may result from kidney disease, dehydration, or severe muscle injury. Low levels can occur with dehydration, overhydration, or certain muscle disorders. Always discuss results with your healthcare provider.
The test works by measuring creatinine, a waste product your muscles produce at a steady rate, in a small blood sample. Because healthy kidneys remove creatinine from the bloodstream, higher-than-normal levels can signal that they are not filtering efficiently, and results are often paired with an estimated glomerular filtration rate (eGFR).
A small blood sample is drawn from a vein in your arm. The lab measures creatinine concentration using a specialized chemical test that detects its presence in the serum.
Reference range
Negative or titer <1:64 at 4°C; clinically significant cold agglutinin titers are generally ≥1:64 to ≥1:256 depending on the reference laboratory. Some laboratories report results as negative, weakly positive, or positive at a specified titer.N/A
No special patient preparation required. Sample should be kept warm (37°C) during and after collection to prevent cold agglutinins from binding to red blood cells in vitro, which can cause spurious hemolysis and falsely altered results.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: Kidney Function and Beyond
Short name
Creatinine
Frequently asked questions
Creatinine levels are a key indicator of kidney function because they reflect how well your kidneys remove waste. Chronic kidney disease is often detected early through repeated creatinine monitoring alongside other markers like blood urea nitrogen (BUN).
It provides a snapshot of your kidneys' ability to filter waste. While it alone doesn’t diagnose kidney disease, it’s often used alongside other tests to assess overall kidney function. High levels may suggest impaired filtration, while persistently low levels could warrant further investigation for conditions like dehydration or muscle disorders.
How often should I get this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy