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Test Code 592 Acetaminophen

Important Note

Human anti-mouse antibodies (hama) may be present in samples from patients who have received immunotherapy or diagnostic procedures utilizing monoclonal antibodies or in individuals who have been regularly exposed to animals. Additionally, other heterophile antibodies, such as human anti-goat antibodies may be present in patient samples. Manufacturers formulate assays to minimize the effects of these antibodies; however careful evaluation of patient results must be done when patients are known to have such antibodies.

Additional Codes


PowerChart: Acetaminophen (Tylenol) Level

MA Cerner: Acetaminophen Level.

Specimen Requirement

0.5 mL lithium heparin serum or plasma is required.

Additional Specimen Collection Information

Serum red-top tube or lithium heparin plasma green-top tube is acceptable. For overdose cases: the specimen is collected 4 hours after the time of suspected ingestion. Serum and plasma gel tubes are NOT acceptable. Serum or plasma should be separated from contact with cells within 2 hours of collection. Refrigerate specimen if unable to assay within 8 hours of collection.

Useful For

Monitoring toxicity in overdose cases, Serum concentration and half-life are the only way to assess degree of intoxication in early stages since other liver function studies (eg, bilirubin, liver function enzymes) will not show clinically significant increases until after tissue damage has occurred, at which point therapy is ineffective.


Monday through Sunday

Routine: Typically completed within 4 hours after arrival at the testing site.

Expedite: Typically completed within 2 hours after specimen arrives at the testing site.

STAT: Typically completed within 1.5 hours after specimen arrives at the testing site.

CPT Code Information

Insurances following Medicare rules: G0480

80329 Analgesics, non-opioid; 1 or 2

LOINC Code Information

3298-7 Acetaminophen [Mass/Volume] In Serum Or Plasma

Test Method

Particle Enhanced Turbidimetric Inhibition Immunoassay; Beckman Coulter

Reference Values

Therapeutic: 10-30 mcg/mL

  • Critical Value: > 40 mcg/mL

Post-ingestion Evaluation:

  • Peak levels are reached between 30 and 60 minutes after oral dose.
  • Overdose cases: the specimen is drawn 4 hours after the time of suspected ingestion.
  • Elimination (half-life) Determination: In addition to monitoring acetaminophen blood levels with respect to time post-ingestion for evaluation of potential hepatoxicity, elimination rate (half-life) of 2 to 3 hours is normal and not associated with toxic damage to the liver. Acetaminophen levels as low as 50 mcg/mL may be toxic when the half-life reaches 12 hours. Half-life determination may be particularly useful in instances where time of ingestion is not known and in following response to therapy. Half-life can be determined by obtaining acetaminophen levels at two accurately timed intervals at least 2 hours apart.