Diagnostic Laboratory Blood Test: What It Is, Why You May Need It, and What to Expect
A blood test that measures the level of barbital, a barbiturate medication, in your serum or plasma to monitor treatment or check for toxicity.
{"Barbital is a sedative-hypnotic medication used to treat certain conditions like seizures","This test checks whether the drug level in your blood is within the therapeutic range","The test helps doctors ensure proper dosing and prevent overdose","Blood is drawn from a vein in your arm for this test","Results help monitor treatment effectiveness and safety"}
Key facts at a glance
- LOINC
- 3370-4
- Short code
- BARB
- Synonyms
- Barbital SerPl-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top serum tube (no anticoagulant) or plasma separator tube (PST)
- Units
- N/A
- Ref low
- 5
- Ref high
- 15
- Critical range
- — – 30 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Gas Chromatography-Mass Spectrometry (GC-MS) or Immunoassay
- CPT
- 80345
- SNOMED
- 395174009
- Specimen volume
- 2-5 mL of blood (minimum 1 mL serum or plasma)
- Stability
- Room temperature: 24 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days
- Hemolysis max
- 100
- Lipemia max
- 100
- Icterus max
- 50
- TAT
- 4–72 hours
- Order
- routine
What is this test and what does it help your doctor learn about your health?
The Barbital blood test measures the amount of barbital (also known as veronal) in your blood. Barbital is a barbiturate—a type of medication that slows down brain activity. While it was once commonly used as a sleep aid and sedative, it is now used much less frequently due to the availability of safer alternatives. This test helps doctors monitor the level of the drug in your body to ensure it is working effectively and safely.
Why might I need this test and what symptoms or conditions can it help diagnose?
Your doctor may order this test if you are currently taking barbital to treat a medical condition. The test is performed to: (1) Make sure the level of medication in your blood is enough to be effective (within therapeutic range), (2) Prevent toxicity by ensuring the dose is not too high, (3) Monitor your response to treatment over time, (4) Check for overdose or poisoning if you have symptoms of too much medication, or (5) Ensure you are taking the medication as prescribed.
How is the test performed and what can I expect during the procedure?
A healthcare professional will draw a small sample of blood from a vein in your arm using a needle. The blood sample will be sent to a laboratory for analysis. The process is quick and typically takes only a few minutes. You may feel a brief stinging sensation when the needle is inserted or removed.
How should I prepare for the test, including any food, drink, or medication instructions?
Your doctor will let you know if you need any special preparation. In general, you should inform your doctor about all medications, supplements, and vitamins you are taking, as some substances may affect the test results. Follow your doctor's instructions regarding timing of your last dose of barbital before the test, as the blood sample may need to be drawn at a specific time—often just before your next scheduled dose (trough level) or at another specific time as directed.
Understanding your test results and what they mean for your ongoing health and care
Your test results will show the concentration of barbital in your blood. Your doctor will interpret these results based on your individual situation, including your medical condition, other medications you are taking, and your overall health. The therapeutic range for barbital varies, so discuss your specific results with your healthcare provider. It is important not to adjust your medication dose based on test results without consulting your doctor.
Reference range
Therapeutic: 5-15 mcg/mL; Toxic: >20 mcg/mL; Lethal: >50 mcg/mLN/A
No fasting required. Specimen should be collected prior to next scheduled dose when monitoring therapeutic levels. Avoid alcohol consumption prior to collection.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings4
Frequently asked questions
Is fasting required before the barbital blood test?
Can other medications affect barbital blood levels?
What happens if my barbital level is too high?
What happens if my barbital level is too low?
How often do I need this test?
Is barbital still commonly prescribed?
Sources
- 1
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- 3
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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 15, 2026. · Read our editorial policy