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Creatinine

Creatinine is a Clinical Chemistry laboratory test reference in the LabPedia Medical Laboratory Library. Serum/plasma creatinine; the most widely used laboratory marker for estimating glomerular filtration rate.

Also known asSerum creatinine; SCr

Overview

Creatinine is a creatine phosphate breakdown product cleared primarily by glomerular filtration (with some tubular secretion).

Clinical Importance

Detect and monitor reduced kidney function

Input for eGFR equations (KDIGO-aligned practice)

Specimen Requirements

  • Specimen: serum or lithium heparin plasma (method- and analyzer-dependent; follow the performing laboratory)
  • Tube: gold/SST (serum separator) or green-top lithium heparin as validated locally
  • Handling: invert gently; allow SST to clot fully before centrifugation; separate promptly
  • Storage: refrigerate serum/plasma if testing is delayed per analyte stability limits
  • Stability: analyte-specific; do not exceed institutional or manufacturer time/temperature limits
  • Fasting: follow institutional/protocol fasting requirements when the ordered pathway requires fasting

Analytical Method

Enzymatic creatinine methods or Jaffe alkaline picrate methods; enzymatic assays generally have fewer interferences. IDMS-traceable calibration is expected for eGFR use.

Instruments Used

Automated analyzers

  • Roche Cobas chemistry and immunoassay systems
  • Abbott Alinity / Architect chemistry and immunoassay systems
  • Siemens Healthineers Atellica / ADVIA chemistry and immunoassay systems
  • Beckman Coulter AU / DxC chemistry systems
  • Beckman Coulter Access / DxI immunoassay systems
  • Mindray BS-series chemistry analyzers
  • Ortho Clinical Diagnostics Vitros systems
  • Thermo Fisher / Indiko and related chemistry platforms
  • Randox clinical chemistry systems

Manual methods

  • Manual spectrophotometric/immunoassay methods in selected reference or backup settings

Reference Values

Typical adult SI examples below follow widely published international clinical chemistry practice (e.g., Tietz; Henry's). Always interpret against the method- and demographics-specific interval printed on the patient report (CLSI EP28-A3c). Neonatal, pediatric, pregnancy, and assay-generation intervals differ.

Example adult serum/plasma creatinine intervals commonly cited in major texts are roughly 45 to 90 µmol/L (0.5 to 1.0 mg/dL) in many women and about 60 to 110 µmol/L (0.7 to 1.2 mg/dL) in many men. Values are muscle-mass-, age-, sex-, and method-dependent (enzymatic vs Jaffe; IDMS-traceable calibration expected for eGFR).

Interpretation

Critical and significant-risk limits are institution-defined (CLSI GP47). Confirm the local call list. Textbook examples are not universal thresholds.

Critical values

  • Acute large rises may trigger institutional notification; verify policy

Common Causes of Increased Results

  • Elevated creatinine suggests reduced GFR, acute kidney injury, or increased generation; interpret with eGFR and trends

Common Causes of Decreased Results

  • Low creatinine may reflect low muscle mass; eGFR equations may overestimate GFR

Clinical Significance

  • CKD and AKI laboratory monitoring
  • Drug dosing GFR estimates

Factors Affecting Results

Pre-analytical

  • Hemolysis, lipemia, or icterus (analyte- and method-dependent interference)
  • IV fluid contamination or draw above an infusion
  • Prolonged tourniquet time; delayed separation of cells
  • Wrong tube additive or incomplete clotting of SST
  • High meat meal may transiently raise creatinine

Analytical

  • Jaffe interferences (bilirubin, some cephalosporins; method-dependent)
  • Non-IDMS calibration invalidates some eGFR equations

Post-analytical

  • Wrong reference interval or unit applied
  • Failure to review delta checks / critical values before release

Advantages and Limitations

Advantages

  • Universal, inexpensive GFR surrogate

Limitations

  • Affected by muscle mass, diet, and some drugs
  • Lags true GFR change in acute settings

Clinical Pearls

Report creatinine with eGFR; a ‘normal’ creatinine can still mean reduced GFR in low-muscle-mass adults.

Related Laboratory Tests

References

Authoritative textbooks, guidelines, and reviews supporting this laboratory test reference. Verify reference intervals, critical limits, and method details against institutional protocols and current guideline editions.

Textbooks

  • Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 8th ed. Elsevier; 2022.
  • McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021.
  • Bishop ML, Fody EP, Schoeff LE. Clinical Chemistry: Principles, Techniques, and Correlations. 9th ed. Jones & Bartlett; 2022.

CLSI and Professional Guidelines

  • International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). Recommendations and reference measurement systems for clinical chemistry measurands (verify current IFCC documents for the analyte).
  • Clinical and Laboratory Standards Institute. Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Approved Standard. CLSI document EP28-A3c. CLSI; 2010.
  • Clinical and Laboratory Standards Institute. Collection of Diagnostic Venous Blood Specimens. CLSI standard GP41. CLSI.
  • American Diabetes Association. Standards of Care in Diabetes. Diabetes Care (annual update).
  • Kidney Disease: Improving Global Outcomes (KDIGO). Clinical Practice Guideline for Evaluation and Management of Chronic Kidney Disease.
  • American Association for the Study of Liver Diseases (AASLD). Practice guidance related to evaluation of abnormal liver chemistries / liver disease laboratory evaluation (verify current AASLD publication and institutional adoption).
  • Kidney Disease: Improving Global Outcomes (KDIGO). Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease (current edition).

Frequently Asked Questions

Common questions about using this Creatinine laboratory test Medical Laboratory Library reference in Medical Laboratory Science education.

What is the Creatinine laboratory test reference used for?

This Medical Laboratory Library page summarizes the clinical importance of Creatinine. Review the Clinical Importance section for why the test is ordered in laboratory medicine practice.

Where can I find Creatinine specimen requirements?

See the Specimen Requirements section on this page for specimen information related to Creatinine. Confirm collection details against your laboratory protocol.

Where are Creatinine reference values listed?

See the Reference Values section on this Laboratory Library page. Reference ranges can vary by method and population, so verify intervals with your laboratory.

How do I interpret Creatinine results?

Use the Interpretation section for laboratory interpretation framing, including increased and decreased result patterns when provided. Do not treat educational text as a patient-specific diagnosis.

What analytical method is used for Creatinine?

See the Analytical Method section for principle and method notes. Method details may differ by instrument and institutional SOP.

Are related laboratory tests linked from Creatinine?

Yes. The Related Laboratory Tests section lists connected references for continued lookup in the Medical Laboratory Library.

How can I continue learning after reading Creatinine?

Use Continue learning links on this page for related Academy lessons, medical laboratory quizzes, or laboratory case studies when available for this Clinical Chemistry topic.

What are the clinical pearls for Creatinine?

See the Clinical Pearls section for concise laboratory practice notes associated with Creatinine. Apply pearls alongside institutional protocols.

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