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Acetamincryareaurnshpf

Published: August 9, 2026Updated: August 16, 2026

This test examines urine under a microscope to detect acetaminophen crystals, which may indicate drug overdose or toxicity.

Quick summary

{"The test looks for acetaminophen (Tylenol) crystals in urine using microscopy","Presence of crystals may indicate overdose or excessive drug accumulation","Results help doctors diagnose and monitor acetaminophen toxicity"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
51213-7
Short code
ACET-UR-HPF
Synonyms
Acetamin Cry #/area UrnS HPF
Category
chemistry
Sample
urine
Container
Sterile urine container (clean-catch or catheter specimen cup)
Units
N/A
Ref low
0
Ref high
0
Critical range
— – 1 N/A
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
microscopy-light-hpf
CPT
81000
SNOMED
271545004
Specimen volume
10-50 mL preferred; minimum 5 mL
Stability
Room temperature: 2 hours; Refrigerated (2-8°C): 24-48 hours. Do not freeze. Analyze as soon as possible to prevent bacterial overgrowth and crystal formation/degradation.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
1–4 hours
Order
routine

What is this test?

The acetaminophen crystals test is a microscopic examination of urine sediment to detect crystals formed by acetaminophen (also known as paracetamol or Tylenol). When someone takes too much acetaminophen, the body may not be able to process it all, leading to crystal formation that can be seen in urine. This test uses a high-power microscope to examine a small sample of urine after it has been spun in a centrifuge.

Why is this test done?

This test is primarily used to help diagnose acetaminophen overdose or toxicity. It may be ordered when a patient has taken too much acetaminophen and is showing symptoms such as nausea, vomiting, abdominal pain, or signs of liver damage. The test can also be used to monitor patients who are being treated for acetaminophen poisoning to see if the drug is being cleared from their system.

How is the test performed?

A urine sample is collected from the patient. The sample is placed in a centrifuge to separate the solid particles (sediment) from the liquid. The sediment is then examined under a high-power microscope to look for characteristic acetaminophen crystals. The results are typically reported as the number of crystals seen per area or high-power field.

What do the results mean?

The presence of acetaminophen crystals in urine may indicate acetaminophen overdose or toxicity. However, the absence of crystals does not rule out toxicity, as crystals may not form in all cases. Your healthcare provider will interpret these results along with other tests (such as blood tests for acetaminophen levels and liver function) to make a complete assessment. Normal results would show no acetaminophen crystals present.

Reference range

No acetaminophen crystals seen; negative for acetaminophen crystalsN/A

Specimen: urine

Collect urine in a sterile, clean-catch container. Female patients should cleanse the urethral area from front to back before collection. Midstream urine collection is preferred to avoid contamination. No special diet or medication restrictions required unless specified by physician.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

Do I need to prepare for this test?
No special preparation is typically required for this test. You should provide a clean urine sample as instructed by your healthcare provider. Inform your doctor about any medications or supplements you are taking, as some substances may affect the results.
Is the test painful?
No, the urine test is not painful. You simply need to provide a urine sample in a sterile container. The microscopic examination is done in a laboratory and causes no discomfort.
How long does it take to get results?
Results are typically available within 1-2 days, depending on the laboratory. Your healthcare provider will contact you with the results or discuss them at your follow-up appointment.
What happens if acetaminophen crystals are found?
If acetaminophen crystals are found, your healthcare provider will evaluate your condition based on your symptoms, the amount of acetaminophen you may have taken, and other test results. Treatment for acetaminophen overdose may include activated charcoal (if taken recently), N-acetylcysteine (the antidote), and close monitoring of liver function.
Can this test detect regular acetaminophen use?
This test is not typically used to detect normal therapeutic use of acetaminophen. It is specifically designed to identify cases of overdose or significant accumulation that leads to crystal formation in the urine.
  1. 1
    MedlinePlus - Acetaminophen overdoseSource
  2. 2
    Mayo Clinic - Acetaminophen (Oral Route)Source
  3. 3
    National Library of Medicine - Urine Sediment AnalysisSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy