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  Acetaminophen (Paracetamol) Toxicity Assessment (Revised 2023)

Time After Ingestion  
Acetaminophen Level  

Important: Inputs must be complete to perform calculation.


Include literature references: Yes   No

  • In this calculator, mcg is the abbreviation for micrograms.
  • This calculator is based on the 2023 revised Rumack and Matthew Nomogram.1 Treatment threshold levels are calculated to be 50% lower than the high-risk drug level.
  • Drug levels done before the 4 hour point may not represent the true peak of absorption.
  • The revised Rumack-Matthew nomogram may be used following an acute acetaminophen ingestion (ie, an ingestion period of ≤24 hours regardless of the ingestion pattern) when the history is reliable and accurate. Use of this nomogram is not appropriate for acute ingestions when the history is unknown or unreliable, or following repeated supratherapeutic ingestions.
  • In this calculation, the revised Rumack nomogram is represented by the following equations:
    • Toxic Level = e(5.703782 - ((Time_After_Ingestion - 4) * 0.175148))
    • Treatment Level = Toxic Level - (0.5 * Toxic Level)

Equations used
ToxLevel = fixDP(e(5.703782-((TimeAfterIngestion-4)*0.175148)),1)
RxLevel = fixDP(ToxLevel - (0.5 * ToxLevel),1)


  1. Dart RC, Mullins ME, Matoushek T, et al. Management of Acetaminophen Poisoning in the US and Canada: A Consensus Statement. JAMA Netw Open. 2023 Aug 1;6(8):e2327739. PubMed ID: 37552484 PubMed Logo
  2. Rumack BH, Matthew H. Acetaminophen poisoning and toxicity. Pediatrics. 1975 Jun;55(6):871-6. PubMed ID: 1134886 PubMed Logo
  3. White SJ, Rumack BH. The acetaminophen toxicity equations: "solutions" for acetaminophen toxicity based on the Rumack-Matthew nomogram. Ann Emerg Med. 2005 May;45(5):563-4. PubMed ID: 15855961 PubMed Logo
  4. Buckley NA, Whyte IM, O'Connell DL, et al. Activated charcoal reduces the need for N-acetylcysteine treatment after acetaminophen (paracetamol) overdose. J Toxicol Clin Toxicol. 1999;37(6):753-7. PubMed ID: 10584587 PubMed Logo
  5. Vale JA, Proudfoot AT. Paracetamol (acetaminophen) poisoning. Lancet. 1995 Aug 26;346(8974):547-52. Review. PubMed ID: 7658783 PubMed Logo


Associated Logical Observation Identifiers Names and Codes [LOINC]
Parameter LOINC's and Suggested Units
Acetaminophen Level 12442-0 : mcg/mL      22736-3 : mcmol/L      3298-7 : mcg/mL      14581-3 : mcmol/L      

This material contains content from LOINC® (http://loinc.org). The LOINC table, LOINC codes, and LOINC panels and forms file are copyright © 1995-2014, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee and available at no cost under the license at http://loinc.org/terms-of-use.

Associated ICD10-CM Codes
   T50.901APoisoning by unspecified drugs, medicaments and biological substances, accidental (unintentional), initial encounter

Associated ICD9-CM Codes
   E850.0Acc poison-analgesic nos
   E950.0Poison-drug/medicin nos
   977.9Poison-medicinal agt nos


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