Complete Blood Count (CBC): What This Common Blood Test Measures and When You May Need It
A urine test to detect the presence of barbiturates (sedative medications) in your system, commonly used for drug screening purposes.
{"This test checks your urine for barbiturates, a type of sedative medication","It is commonly used in workplace, clinical, or forensic drug screening","A positive result means barbiturates were detected above the testing threshold","Results should be confirmed with more specific testing if needed","Certain medications and substances may cause false positives"}
Key facts at a glance
- LOINC
- 19355-7
- Short code
- BARBU
- Synonyms
- Barbital CtO Ur Scn-mCnc
- Category
- chemistry
- Sample
- urine
- Container
- Sterile urine collection container without preservatives
- Units
- N/A
- Ref high
- 200
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- screen
- CPT
- 80307
- SNOMED
- 102689003
- Specimen volume
- 30 mL
- Stability
- Room temperature: 24 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C): 30 days
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 1–24 hours
- Order
- routine
What is this test? A complete blood count, or CBC, is a routine blood test that measures the different cells in your blood, including red blood cells, white blood cells, and platelets. It gives your healthcare provider a broad picture of your overall health and can help detect a wide range of conditions, from infections and anemia to blood disorders.
The Barbital cutoff test is a screening test that analyzes your urine to detect the presence of barbiturates. Barbiturates are a class of sedative-hypnotic medications that were historically prescribed for anxiety, sleep disorders, and seizures. Examples include phenobarbital, pentobarbital, secobarbital, and amobarbital. This test uses a cutoff concentration to determine whether the result is positive or negative for barbiturate use.
How is the test performed? A healthcare professional will draw a small sample of blood, usually from a vein in your arm, using a thin needle. The process takes only a few minutes. After the sample is collected, it is sent to a laboratory where a machine analyzes the number, size, and types of blood cells in your sample.
A urine sample is collected in a clean container. The sample is then analyzed using immunoassay screening methods that detect the presence of barbiturates or their metabolites. If the concentration of barbiturates meets or exceeds the predetermined cutoff level, the result is reported as positive. If below the cutoff, the result is reported as negative.
Why might I need this test? Your provider may order a CBC as part of a routine checkup, to investigate symptoms such as fatigue, weakness, fever, unusual bruising, or unexplained weight loss, to monitor an existing condition like anemia or an infection, or to track how treatments such as chemotherapy or certain medications are affecting your blood cells.
This test is commonly ordered for several reasons: pre-employment drug screening, random workplace testing, monitoring patients on barbiturate therapy, legal or forensic investigations, and substance abuse evaluation. It may also be ordered if your healthcare provider suspects barbiturate use or overdose.
What do the results mean? Your results will show whether your red blood cell, white blood cell, and platelet counts fall within normal ranges. Low red blood cell counts may suggest anemia, while high white blood cell counts can point to an infection or inflammation. Abnormal results do not always mean a serious problem, and your healthcare provider will interpret them together with your symptoms, medical history, and other tests to decide what follow-up, if any, is needed.
A NEGATIVE result means no barbiturates were detected in your urine at or above the testing cutoff level. This does not necessarily mean no barbiturates were used—it may mean the amount is too small to detect or the drug has been eliminated from your system. A POSITIVE result indicates that barbiturates were detected at or above the cutoff level. Positive results typically require confirmatory testing with a more specific method like gas chromatography-mass spectrometry (GC-MS) to confirm the presence and identify the specific barbiturate.
Reference range
Negative (below cutoff threshold)N/A
No special preparation required. Patients should be informed that certain prescription and over-the-counter medications may produce positive results.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Barbiturates were commonly prescribed in the past but have largely been replaced by safer alternatives (such as benzodiazepines) due to their high risk of dependence, overdose, and narrow therapeutic index. Detection of barbiturates in urine screening may indicate legitimate therapeutic use, misuse, or illicit use. Phenobarbital is still used for seizure control, so patients with epilepsy may have legitimate positive results. Healthcare providers interpret results in context of the patient's medical history, medications, and clinical presentation.
Important considerations: Barbiturates can remain detectable in urine for several days to weeks after use, depending on the specific drug and individual factors such as metabolism, age, and kidney function. False positives may occur with certain antibiotics, analgesics, or other substances that cross-react with the screening assay. Always inform the testing facility of all medications and supplements you are taking.
Frequently asked questions
How long do barbiturates stay in my urine?
Can a positive result occur from my legitimate prescription?
What can cause a false positive result?
Is this test painful?
Do I need to prepare for this test?
Sources
- 1
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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