Diagnostic Blood Test: What It Is, How It Is Done, and What Your Results Mean
A confirmatory blood test that measures benzodiazepine levels to monitor medication use or detect potential overdose.
{"This test measures the amount of benzodiazepines in your blood","It confirms the presence and amount of these medications","Sample is collected from a vein in your arm","Results help doctors ensure proper dosing or diagnose overdose","Results are typically available within a few days"}
Key facts at a glance
- LOINC
- 42586-8
- Short code
- BENZO-CONF
- Synonyms
- Benzodiaz Bld Cfm-mCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Gray-top sodium fluoride/potassium oxalate blood collection tube (preferred for forensic/toxicology) or red-top serum tube; EDTA tube acceptable for plasma analysis
- Units
- N/A
- Ref low
- 0
- Ref high
- 200
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- confirm
- CPT
- 80347
- SNOMED
- 313417009
- Specimen volume
- 5-10 mL whole blood
- Stability
- Stable for 7 days at 2-8°C; for prolonged storage, freeze at -20°C or below. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 24–72 hours
- Order
- routine
What is this test? This is a laboratory test that measures substances in a sample of your blood to help your doctor check how your body is working, screen for certain health conditions, or monitor a treatment you may already be receiving.
The Benzodiazepine Blood Test is a confirmatory laboratory test that measures the amount of benzodiazepines in your whole blood. Benzodiazepines are a class of prescription medications commonly used to treat anxiety, sleep disorders, muscle spasms, and seizures. Examples include diazepam (Valium), lorazepam (Ativan), alprazolam (Xanax), and clonazepam (Klonopin).
How is the test performed? A trained healthcare professional will draw a small amount of blood, usually from a vein in your arm, using a thin needle. The sample is then sent to a laboratory for analysis, and the collection itself typically takes only a few minutes.
A healthcare professional will draw a blood sample from a vein in your arm using a needle. The blood is collected into a special tube and sent to a laboratory for analysis. The confirmatory method typically uses advanced techniques like gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS) to accurately identify and measure benzodiazepine levels.
Why might I need this test? Your doctor may order this test to help diagnose the cause of symptoms you are experiencing, to screen for health problems before they cause symptoms, to check how well an organ is working, or to monitor how well a treatment is working over time.
Your doctor may order this test for several reasons: to monitor proper medication levels in your blood, to ensure you are taking your prescribed dose, to check for drug compliance, to evaluate symptoms of possible overdose or toxicity, or to detect unauthorized use of these medications. It may also be used in emergency situations when someone shows signs of benzodiazepine overdose.
What should I do to prepare? Follow any specific instructions your doctor gives you. Depending on the test, you may need to fast for 8 to 12 hours beforehand, drink plenty of water, or temporarily avoid certain medications. Tell your care team about all medicines and supplements you take.
Follow your doctor's instructions regarding taking your regular medications before the test. Inform your doctor about all prescription drugs, over-the-counter medications, and supplements you are taking. There is typically no fasting required for this blood test. If you have any concerns about how your medication might affect the test results, discuss them with your healthcare provider.
Understanding your results: Your report will show your values compared with a reference range, which is the range of values seen in most healthy people. A value outside that range does not always mean you are ill, so your doctor will review the results with you and explain what they mean for your health.
Your test results will show whether benzodiazepines are detected in your blood and potentially at what level. Therapeutic ranges vary depending on the specific medication. Your doctor will interpret the results based on your medical history, the specific medication you are taking, and your current symptoms. Results above the therapeutic range may indicate overdose, while subtherapeutic levels may suggest non-compliance or rapid metabolism.
Reference range
Negative: < cutoff concentration (typically 100-200 ng/mL depending on specific benzodiazepine); Positive results reported with quantitative value. Cutoff values vary by laboratory and specific benzodiazepine analyte (e.g., diazepam, nordiazepam, oxazepam, temazepam, alprazolam, clonazepam, lorazepam, midazolam).N/A
No fasting required. Patient should be informed that benzodiazepines are detected in blood for varying durations depending on the specific drug, dose, and chronicity of use. Short-acting benzodiazepines may be detectable for 1-3 days, while long-acting metabolites (e.g., nordiazepam) may persist for weeks after chronic use.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is clinically significant for therapeutic drug monitoring (TDM), ensuring that patients maintain effective yet safe levels of benzodiazepines. It helps healthcare providers adjust dosages to achieve optimal therapeutic effects while minimizing side effects. The confirmatory method is highly specific and can distinguish between different benzodiazepines, which is important for patients on multiple medications.
In cases of suspected overdose, this test helps confirm benzodiazepine involvement and guides appropriate treatment. Benzodiazepine overdose can cause severe sedation, respiratory depression, and coma. Knowing the exact levels helps emergency physicians provide targeted care. The test is also valuable in forensic and addiction medicine settings to verify medication adherence or detect misuse.
Frequently asked questions
Will the test show which specific benzodiazepine I'm taking?
How long do benzodiazepines stay detectable in blood?
Can the test results be affected by other substances?
Do I need to stop taking my benzodiazepine medication before the test?
Is this test painful?
Sources
- 1
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- 3
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.
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