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Cannabinoid (THC and metabolites) in whole blood

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

This test measures levels of tetrahydrocannabinol (THC) and its active metabolites in your blood, often used to assess recent cannabis use.

Quick summary

["Checks for recent cannabis exposure and its effects on your system."]

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

Key facts at a glance

LOINC
73920-1
Short code
JWH-018 4/5OH-pentyl Bld Ql
Synonyms
JWH-018 4/5OH-pentyl Bld Ql
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What Does This Test Measure?

The test detects THC and its metabolites (like THC-COOH) in your blood. These compounds are present when you use cannabis and can remain detectable for several days after use, depending on factors like frequency of use and metabolism.

Why Might You Need This Test?

This test may be ordered by healthcare providers to evaluate recent cannabis use, assess impairment, or support legal or employment-related decisions. It’s also used in some medical settings to monitor substance use disorders or treatment compliance.

How Is the Sample Collected?

A small blood sample is drawn from a vein in your arm by a healthcare professional. The blood is then sent to a lab for analysis.

What Are Common Uses?

Common reasons for this test include workplace drug screening, legal proceedings (e.g., DUIs), medical evaluations for substance use, or monitoring chronic cannabis use in certain clinical settings.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: This test helps determine recent cannabis exposure and can indicate impairment or ongoing use. Elevated levels may correlate with acute effects (e.g., altered perception, mood changes) or longer-term health considerations, though interpretation depends on clinical context and patient history.

Short name

THC Blood Test

Frequently asked questions

How long does it take to get results?
Results are typically available within 1–3 business days, depending on the lab’s processing time. Your healthcare provider will discuss the results with you.
Can I eat or drink before this test?
No special preparation is needed. However, avoid smoking or consuming cannabis products for at least 24 hours before testing if possible, as this may affect results.
Does this test detect other drugs?
No, this test specifically measures THC and its metabolites. Other drug screens (e.g., urine tests) may detect different substances like opioids, cocaine, or alcohol.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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