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Paracetamol (acetaminophen) mg/L → µmol/L

Convert paracetamol (acetaminophen) from mg/L to µmol/L

Sources last checked: 2026-11-03

Paracetamol (acetaminophen) mg/L → µmol/L

Convert paracetamol (acetaminophen) from mg/L to µmol/L

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Converts units only; reference ranges depend on the laboratory, the assay and the patient.

Source: AMA Manual of Style, 11th ed. (Oxford Academic) — Units of measure converter, Table 2: Selected laboratory tests and conversion factors.Open

What is the Paracetamol (acetaminophen) mg/L → µmol/L?

Serum paracetamol (acetaminophen) is reported in mg/L (identical to µg/mL) by many laboratories, including those in Germany, Austria, Turkey and the UK, and in µmol/L by some laboratories in SI-reporting countries. This converter multiplies by 6.616, the factor that follows from the molar mass of paracetamol (151.16 g/mol).

When to use it

  • Comparing a paracetamol level in mg/L with a treatment nomogram or protocol printed in µmol/L
  • Communicating a level to a poison centre or colleague who works in µmol/L
  • Documenting a level for a patient transferred between health systems
  • Toxicology exam questions

When not to use it

  • Staggered overdoses, repeated supratherapeutic ingestion or an unknown time of ingestion — single-level nomograms do not apply, whatever the unit
  • Levels drawn before absorption is complete, which cannot be plotted on a nomogram
  • Deciding on treatment from the converted number alone: treatment lines differ between countries and guidelines

How it is calculated

Paracetamol (µmol/L) = paracetamol (mg/L) × 6.616

Clinical pearls and limitations

  • Converts units only; reference ranges depend on the laboratory, the assay and the patient.
  • 1 mg/L = 1 µg/mL = 6.616 µmol/L; conversely 1 µmol/L = 0.1511 mg/L.
  • A nomogram is defined in one unit and against time since ingestion; convert the level into the nomogram's unit before plotting, and check that the time axis starts from the actual ingestion time.
  • Modified-release preparations, co-ingested drugs that slow gastric emptying and very large ingestions can produce delayed peaks; local protocols often require a repeat level.
  • High bilirubin and some other substances can interfere with enzymatic paracetamol assays; discuss unexpected results with the laboratory.

Frequently asked questions

How do I convert paracetamol from mg/L to µmol/L?

Multiply by 6.616. For example, 85 mg/L × 6.616 = 562 µmol/L and 42 mg/L × 6.616 = 278 µmol/L.

Why is the paracetamol factor 6.616?

Paracetamol has a molar mass of 151.16 g/mol. 1 mg/L ÷ 151.16 g/mol = 0.006616 mmol/L, which is 6.616 µmol/L.

Is mg/L the same as µg/mL for paracetamol?

Yes. 1 mg/L = 1 µg/mL exactly, so the many nomograms labelled in µg/mL can be read directly with a mg/L result.

Evidence and guidelines

  1. Primary source: AMA Manual of Style, 11th ed. (Oxford Academic) — Units of measure converter, Table 2: Selected laboratory tests and conversion factors.
  2. PubChem compound summary: acetaminophen (paracetamol) (CID 1983), molecular weight 151.16 g/mol.

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For healthcare professionals and medical students. These tools support, and do not replace, clinical judgement. Always check results against the original source and your local protocols.