Understanding Your Laboratory Test: A Patient's Guide to the Procedure, Results, and Possible Risks
A test to measure the level of barbiturate medications in your blood to monitor treatment or check for overdose.
{"Measures barbiturate drug levels in blood serum or plasma","Used to monitor therapeutic drug levels and detect poisoning","Sample collected via blood draw from a vein","Results help doctors adjust medication dosage safely"}
Key facts at a glance
- LOINC
- 10338-2
- Short code
- BARB
- Synonyms
- Barbiturates SerPl-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top (no gel) or serum separator tube (SST); alternatively, lavender-top (EDTA) or green-top (heparin) plasma tubes acceptable. Avoid gel separator tubes for certain confirmatory assays.
- Units
- N/A
- Ref low
- 15
- Ref high
- 40
- Critical range
- — – 10000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–99 years
- Method
- Immunoassay (EIA/EMIT) for screening with confirmation by Gas Chromatography-Mass Spectrometry (GC-MS) or Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
- CPT
- 80307
- SNOMED
- 3932004
- Specimen volume
- 5-10 mL of whole blood yielding at least 2-3 mL of serum or plasma; minimum 1 mL for screening assays
- Stability
- Room temperature: 24 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days for long-term storage. Protect from light. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 100
- Lipemia max
- 100
- Icterus max
- 50
- TAT
- 1–72 hours
- Order
- routine
What is this test, and what exactly does it measure or look for in my body?
The barbiturates test measures the amount of barbiturate drugs in your blood serum or plasma. Barbiturates are medications that act on the central nervous system, primarily used for sedation, anesthesia, and seizure control. Common barbiturates include phenobarbital, pentobarbital, and secobarbital.
Why has this test been ordered for me, and what health conditions can it help detect, diagnose, or monitor over time?
This test is performed for several reasons: to monitor therapeutic drug levels in patients taking barbiturates for epilepsy or other conditions, to check for drug overdose or poisoning, to ensure drug levels are within the therapeutic range (not too high to cause toxicity, not too low to be ineffective), and to help diagnose the cause of unexplained symptoms like drowsiness, confusion, or breathing problems.
How is this test performed, and what should I expect during the procedure, including any preparation I need to do beforehand?
A healthcare professional will draw a small 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 test measures the concentration of barbiturates in micrograms per milliliter (μg/mL) or milligrams per liter (mg/L).
What do my test results mean, and how will my doctor use them to guide my diagnosis and treatment plan?
Results are interpreted based on the specific barbiturate being measured and its therapeutic range. Generally, therapeutic levels vary by drug: Phenobarbital: 10-40 μg/mL, Pentobarbital: 1-5 μg/mL. Levels above the therapeutic range may indicate overdose or toxicity, while levels below may indicate subtherapeutic dosing. Your doctor will interpret your results considering your medical history, symptoms, and other factors.
Are there any risks, side effects, or complications from this test that I should be aware of before the procedure?
The risks of this test are minimal and include slight pain or bruising at the puncture site, rare infection, or fainting. These risks are similar to routine blood tests.
Reference range
Negative: < 200 ng/mL (cutoff varies by laboratory and assay); Therapeutic ranges vary by specific barbiturate: Phenobarbital 15-40 mcg/mL, Pentobarbital 1-5 mcg/mL, Secobarbital 1-2 mcg/mL, Thiopental 1-5 mcg/mLN/A
No fasting required. Specimen should be collected prior to next scheduled dose for therapeutic drug monitoring. Patient identity and chain of custody documentation required for forensic or workplace testing. Avoid specimen collection from indwelling catheters that may contain residual medication.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings2
Frequently asked questions
Do I need to fast before this test?
How long does it take to get results?
What should I tell my doctor before the test?
What are the symptoms of barbiturate overdose?
Can this test detect all types of barbiturates?
Sources
- 1
- 2
- 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 15, 2026. · Read our editorial policy