Overview
Ammonia is a neurotoxic nitrogenous waste measured in plasma by enzymatic or electrode methods.
Clinical Importance
Evaluate unexplained encephalopathy with liver disease
Urea-cycle disorder pathways
Specimen Requirements
- Specimen: plasma (EDTA or heparin per method)
- Tube: as validated locally (often EDTA or heparin); fill completely
- Handling: place on ice immediately; separate promptly; assay without delay
- Stability: ammonia rises rapidly with delayed processing, hemolysis, and high ambient temperature
Analytical Method
Enzymatic glutamate dehydrogenase methods or ion-selective approaches.
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.
Typical published adult plasma ammonia often <50 µmol/L; method-specific. Neonatal intervals differ.
Interpretation
Critical and significant-risk limits are institution-defined (CLSI GP47). Confirm the local call list. Textbook examples are not universal thresholds.
Critical values
- Markedly elevated ammonia may be critical; verify locally
Common Causes of Increased Results
- Hyperammonemia; hepatic failure, shunting, urea-cycle defects, or artifact
Common Causes of Decreased Results
- Not typically interpreted
Clinical Significance
- Encephalopathy laboratory support
Factors Affecting Results
Pre-analytical
- Delayed processing, hemolysis, fist clenching, and smoking; major false elevations
Analytical
- Calibration/QC failure; reagent lot shifts
- Carryover or substrate depletion on high-throughput analyzers
- Assay-specific interference (heterophile antibodies for immunoassays)
Post-analytical
- Acting on ammonia without preanalytical review
Advantages and Limitations
Advantages
- Direct ammonia measure
Limitations
- One of the most artifact-prone chemistry tests
Clinical Pearls
If ammonia is high but the draw was warm and delayed, repeat correctly before calling urea-cycle crisis.
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).
Frequently Asked Questions
Common questions about using this Ammonia laboratory test Medical Laboratory Library reference in Medical Laboratory Science education.
What is the Ammonia laboratory test reference used for?
This Medical Laboratory Library page summarizes the clinical importance of Ammonia. Review the Clinical Importance section for why the test is ordered in laboratory medicine practice.
Where can I find Ammonia specimen requirements?
See the Specimen Requirements section on this page for specimen information related to Ammonia. Confirm collection details against your laboratory protocol.
Where are Ammonia 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 Ammonia 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 Ammonia?
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 Ammonia?
Yes. The Related Laboratory Tests section lists connected references for continued lookup in the Medical Laboratory Library.
How can I continue learning after reading Ammonia?
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 Ammonia?
See the Clinical Pearls section for concise laboratory practice notes associated with Ammonia. Apply pearls alongside institutional protocols.
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