Overview
Glucose quantifies circulating hexose concentration used to detect and monitor dysglycemia.
Clinical Importance
Evaluate hyperglycemia/hypoglycemia
Screen and monitor diabetes pathways (with HbA1c and clinical criteria)
Specimen Requirements
- Specimen: plasma (or whole blood for some point-of-care methods)
- Tube: gray-top sodium fluoride / potassium oxalate (or fluoride-EDTA) when glycolysis inhibition is required
- Alternative: lithium heparin or serum may be accepted if separated promptly; follow local method
- Handling: mix gently; separate cells promptly unless using a validated glycolysis inhibitor tube
- Stability: glucose falls in unseparated whole blood without inhibitor; lactate rises with delayed processing/exercise/tourniquet
Analytical Method
Most automated methods use enzymatic hexokinase or glucose oxidase reactions with photometric or electrochemical detection.
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 fasting plasma glucose interval commonly cited in major clinical chemistry texts: about 3.9 to 5.5 mmol/L (70 to 99 mg/dL). Reference intervals vary by method, specimen type, population, and laboratory validation.
Diagnostic cutoffs (ADA/WHO) for diabetes and impaired fasting glucose are clinical criteria; they are not identical to every laboratory reference interval. Use the report interval and current guideline cutoffs as intended.
Interpretation
Critical and significant-risk limits are institution-defined (CLSI GP47). Confirm the local call list. Textbook examples are not universal thresholds.
Critical values
- Marked hypo- or hyperglycemia commonly appear on critical lists; verify local thresholds
Common Causes of Increased Results
- Hyperglycemia relative to fasting/random criteria and clinical context
Common Causes of Decreased Results
- Hypoglycemia; confirm with critical-value policy and clinical correlation
Clinical Significance
- Diabetes screening/monitoring pathways
- Acute care metabolic assessment
- Point-of-care correlation with laboratory methods when indicated
Factors Affecting Results
Pre-analytical
- Glycolysis in unseparated whole blood without fluoride/prompt separation
- Not truly fasting when a fasting value is required
- IV dextrose contamination
Analytical
- Calibration/QC failure; reagent lot shifts
- Carryover or substrate depletion on high-throughput analyzers
- Assay-specific interference (heterophile antibodies for immunoassays)
- Extreme ascorbic acid or other method-specific interferents
Post-analytical
- Confusing mmol/L and mg/dL (× 18 conversion)
- Applying diagnostic cutoffs without knowing sample type (plasma vs whole blood POC)
Advantages and Limitations
Advantages
- Widely available, rapid, standardized enzymatic methods
Limitations
- Single glucose does not replace HbA1c for chronic glycemic assessment
- POC whole-blood results may differ from laboratory plasma glucose
Clinical Pearls
If plasma glucose seems unexpectedly low, ask whether the tube sat unseparated; glycolysis is a classic false low.
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).
- American Diabetes Association. Standards of Care in Diabetes. Diabetes Care (current annual standards).
Frequently Asked Questions
Common questions about using this Glucose laboratory test Medical Laboratory Library reference in Medical Laboratory Science education.
What is the Glucose laboratory test reference used for?
This Medical Laboratory Library page summarizes the clinical importance of Glucose. Review the Clinical Importance section for why the test is ordered in laboratory medicine practice.
Where can I find Glucose specimen requirements?
See the Specimen Requirements section on this page for specimen information related to Glucose. Confirm collection details against your laboratory protocol.
Where are Glucose 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 Glucose 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 Glucose?
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 Glucose?
Yes. The Related Laboratory Tests section lists connected references for continued lookup in the Medical Laboratory Library.
How can I continue learning after reading Glucose?
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 Glucose?
See the Clinical Pearls section for concise laboratory practice notes associated with Glucose. Apply pearls alongside institutional protocols.
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