Acetaminophen Blood Test (Paracetamol Level)
Reviewed
Also called: Acetaminophen level, Paracetamol level, Acetaminophen drug test
This test measures acetaminophen—called paracetamol in many countries—in blood when overdose or toxicity may be a concern.
Specimen: Blood (serum or plasma; method depends on the laboratory)
Urgent safety information
A possible acetaminophen/paracetamol overdose needs urgent medical or poison-centre advice even when the person feels well. Do not wait for symptoms or use this page to decide that an exposure is safe.
Why this test may be ordered
- A known or possible overdose
- Uncertain ingestion time or amount
- Symptoms or laboratory findings that could indicate medicine-related liver injury
Preparation and collection
This is commonly an urgent test. Do not delay emergency assessment to fast or prepare. Bring medicine packets and give the clinical team the best possible ingestion time and amount.
A health professional usually takes a small blood sample from a vein. Collection normally takes only a few minutes.
Blood collection has a small risk of brief discomfort, bruising, light-headedness, or rarely infection at the needle site.
Understanding results
Interpretation depends on the measured concentration, the time since ingestion, whether exposure was acute or repeated, the assay and units, and other clinical findings. A number without reliable timing can be misleading.
- Detected concentration: The medicine is present in the tested sample. Limitation: The concentration cannot be judged safely without timing, units, exposure pattern, and clinical context. Next step: Urgent clinician or poison-centre interpretation; repeat testing or liver tests may be required.
- Not detected or below reporting limit: The assay did not measure a concentration above its reporting limit. Limitation: An early sample, delayed presentation, repeated exposure, or assay limitations may still matter. Next step: Follow the emergency team's advice; do not treat one result as proof that no risk exists.
- A time-dependent treatment nomogram is not appropriate for every exposure pattern.
- Unknown timing, repeated supratherapeutic use, delayed absorption, combination products, and liver injury require separate clinical assessment.
- Units and assay reporting differ; values must not be converted or compared casually.
What to do next
The treating team may combine the result with ingestion history, liver tests, clotting tests, kidney function, glucose, acid-base status, and repeat concentrations. Treatment decisions belong to urgent clinical care.
- Does the sample timing allow this concentration to be interpreted reliably?
- Is this an acute single ingestion or a repeated/unknown exposure pattern?
- Are repeat concentrations or liver-injury tests needed?
Evidence source
U.S. National Library of Medicine: Acetaminophen Blood Test (Paracetamol Level)