Which lab study is the basis for the diagnosis and treatment of acetaminophen toxicity/poisoning?

Updated: Jan 17, 2020
  • Author: Susan E Farrell, MD; Chief Editor: Michael A Miller, MD  more...
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The serum acetaminophen (APAP) concentration is the basis for diagnosis and treatment.  It is important to measure, even in the absence of clinical symptoms, because of the delay in onset of clinical toxicity. After a single ingestion, N-acetylcysteine (NAC) therapy is guided by the serum APAP concentration. An APAP level 4 hours post ingestion of greater than 150 mcg/mL (> 993 µmol/L) reflects possible toxicity.

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