Sign in →

Test Code ACMA Acetaminophen, Serum

Reporting Name

Acetaminophen, S

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

Monitoring toxicity in overdose cases

Method Name


Specimen Type


Specimen Required


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.5 mL

Collection Instructions:

1. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 7 days
  Frozen  180 days
  Ambient  24 hours

Reject Due To

Gross hemolysis Reject


The normal half-life is less than 4 hours, while the toxic half-life is greater than 4 hours.


The toxic level is dependent on half-life. When the half-life is 4 hours, hepatotoxicity generally will not occur unless the concentration is above 150 mcg/mL. The level at which toxicity occurs decreases with increasing half-life until it is encountered at values as low as 50 mcg/mL when the half-life reaches 12 hours.


For half-life determination, draw 2 specimens at least 4 hours apart and note the exact time of each draw. Half-life can be calculated from the concentrations and the time interval.

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
ACMA Acetaminophen, S 3298-7


Result ID Test Result Name Result LOINC Value
ACMA Acetaminophen, S 3298-7


If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.