Unit Converter
Acetaminophen
Synonyms:
- Paracetamol
- Acetaminophen
- Hydroxyacetanilide
- APAP
- p-Acetamidophenol
- p-Hydroxyacetanilide
- N-(4-Hydroxyphenyl)acetanilide
- Acetamidophenol
- N-Acetyl-p-aminophenol
- Acephen
- Acetaco
- Tylenol
- Anacin 3
- Datril
- Panadol
- Acamol
- Algotropyl
Units of Measurement:
- µmol/L
- mcmol/L
- umol/L
- µM/L
- mcM/L
- uM/L
- mg/dL
- mg/100mL
- mg%
- mg/mL
- µg/mL
- mcg/mL
- ug/mL
- microg/mL
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ACETAMINOPHEN
Synonyms
Acetaminophen, Paracetamol, APAP, PCM, N-acetyl-para-aminophenol
Units of Measurement
mg/L, mg/dL, µg/mL, µg/L, mmol/L, µmol/L
Description
Acetaminophen (Paracetamol, APAP) is a widely used analgesic and antipyretic medication. It is safe at therapeutic doses but has a narrow safety margin. Overdose can cause severe hepatic injury due to accumulation of the toxic metabolite NAPQI, especially when glutathione stores are depleted.
Laboratory measurement of acetaminophen concentration is essential for diagnosing acute or chronic overdose, determining the need for N-acetylcysteine (NAC) therapy, and assessing the risk of hepatotoxicity using the Rumack–Matthew Nomogram.
Physiological & Metabolic Role
Acetaminophen acts centrally by inhibiting prostaglandin synthesis.
Metabolism occurs in the liver via:
- Glucuronidation and sulfation (safe pathways)
- CYP2E1 metabolism to NAPQI (toxic; detoxified by glutathione)
Excess formation of NAPQI leads to hepatocellular necrosis.
Clinical Significance
Elevated Levels
- Acute overdose
- Repeated supratherapeutic ingestion
- Chronic alcoholism (induces CYP2E1)
- Malnutrition
- Liver disease
- Delayed gastric emptying or extended-release formulations
Low/Undetectable Levels
- No recent ingestion
- Delayed presentation (>24–36 hours)
- After NAC therapy
Reference Intervals (Therapeutic & Toxic Levels)
(Tietz 8E + Mayo Clinic + ARUP verified)
| Interpretation | Concentration |
| Therapeutic range | 10–20 µg/mL (66–132 µmol/L) |
| Potential toxicity (4 hours post ingestion) | >150 µg/mL (>990 µmol/L) |
| High risk for hepatotoxicity | >200 µg/mL at 4 hours |
| Minimal risk | <100 µg/mL at 4 hours |
Therapeutic and toxic thresholds apply to single acute ingestion and must be interpreted with the Rumack–Matthew Nomogram.
Rumack–Matthew Nomogram
Used to predict hepatotoxicity after single acute ingestion.
Testing guidelines:
- Draw first level ≥4 hours after ingestion.
- Levels above the treatment line indicate the need for NAC therapy.
- If ingestion time is unclear or >8 hours → start NAC immediately.
Indicators of Acetaminophen Toxicity
- Nausea, vomiting
- Abdominal/RUQ pain
- Elevated AST/ALT (>1000 U/L)
- Metabolic acidosis
- Elevated INR
- Hyperbilirubinemia
- Hepatic encephalopathy (late stage)
Massive overdose may cause early lactic acidosis and renal failure.
Units Description & Conversion Factors
Molecular weight ≈ 151.16 g/mol
Unit Meanings
| Unit | Meaning |
| µg/mL | microgram per milliliter |
| mg/L | milligram per liter |
| mg/dL | milligram per deciliter |
| µmol/L | micromole per liter |
Conversions
- 1 µg/mL = 1 mg/L
- µg/mL → µmol/L:
µmol/L=µg/mL×6.62\text{µmol/L} = \text{µg/mL} \times 6.62µmol/L=µg/mL×6.62 - mg/L → µmol/L:
µmol/L=mg/L×6.62\text{µmol/L} = \text{mg/L} \times 6.62µmol/L=mg/L×6.62 - µmol/L → µg/mL:
µg/mL=µmol/L÷6.62\text{µg/mL} = \text{µmol/L} \div 6.62µg/mL=µmol/L÷6.62
Clinical Pearls
- NAC is most effective when started within 8 hours of overdose.
- Chronic alcohol use increases toxicity even at lower doses.
- Children have more sulfate conjugation → slightly safer metabolism.
- Early levels (<4 hours) are unreliable and should not be used for decision-making.
- Detectable APAP level + elevated ALT/AST → treat with NAC regardless of nomogram.
Interesting Fact
Acetaminophen overdose is the leading cause of acute liver failure in multiple countries. The development of N-acetylcysteine in the 1970s dramatically reduced mortality.
SEO Unit Converter Text
Acetaminophen level conversion calculator for medical laboratories. Convert acetaminophen/Paracetamol levels between µg/mL, mg/L, mg/dL, and µmol/L using molecular weight–based conversions. Includes therapeutic ranges, toxic levels, and nomogram-based clinical interpretation.
References
- Tietz Clinical Chemistry and Molecular Diagnostics, 8th Edition — Toxicology & Therapeutic Drug Monitoring.
- Mayo Clinic Laboratories — Acetaminophen, Serum Test Catalogue.
- ARUP Consult — Acetaminophen Toxicity Guidance.
- NIH LiverTox Database — Acetaminophen Toxicity.
- Hodgman MJ, Garrard AR. “A Review of Acetaminophen Poisoning.” NEJM.
- Rumack BH. “Acetaminophen overdose and toxicity.” Pediatrics.
- American College of Medical Toxicology (ACMT) Guidelines.