Complete Blood Count (CBC) Test: What You Need to Know

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

This test confirms the presence of barbiturates (sedative medications) in urine using a specific confirmatory method to verify initial screening results.

Quick summary

{"This test confirms whether barbiturates are present in your urine after an initial screening test shows a positive result","Barbiturates are prescription sedative medications used for anxiety, sleep disorders, or seizure control","The confirmatory method is more specific and accurate than initial screening tests","Results are reported as positive or negative based on a established cutoff threshold","This test is commonly used for legal, employment, or medical monitoring purposes"}

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

Key facts at a glance

LOINC: 19276-5
Short code: BARBCFM
Synonyms: Barbiturates CtO Ur Cfm-mCnc
Category: chemistry
Sample: urine
Container: Sterile, preservative-free urine container; preferred specimen containers are forensic-grade specimen cups with tamper-evident seals for chain-of-custody testing
Units: N/A
Ref low: 0
Ref high: 200
Critical range: — – 10000 N/A
Fasting: false
Population: adult
Sex: all
Age range: 18–65 years
Method: confirm
CPT: 80345 (confirmatory testing)
SNOMED: 167399001
Specimen volume: 10-30 mL of random urine; minimum 5 mL required for confirmatory analysis
Stability: Refrigerated (2-8°C): up to 7 days. Frozen (-20°C or below): up to 1 month. Room temperature: up to 48 hours. Avoid repeated freeze-thaw cycles.
Hemolysis max: 0
Lipemia max: 0
Icterus max: 0
TAT: 24–72 hours
Order: routine

What is a complete blood count (CBC) test and what does it measure in your blood?

A barbiturate confirmatory test is a specialized laboratory test performed on a urine sample to confirm the presence of barbiturates. Barbiturates are a class of prescription medications that act as central nervous system depressants, commonly used to treat anxiety, insomnia, and seizure disorders. After an initial screening test shows a positive result, this confirmatory test uses more advanced techniques (such as gas chromatography-mass spectrometry or liquid chromatography-tandem mass spectrometry) to definitively identify and quantify barbiturates in your urine.

How is a complete blood count (CBC) test performed, and what can you expect during the blood draw?

You will be asked to provide a urine sample in a clean container. The sample is then sent to a laboratory where technicians use highly sensitive and specific equipment to analyze its contents. The confirmatory method looks for specific barbiturate compounds and their metabolites. Unlike screening tests that provide yes/no results, this test can identify exactly which barbiturates are present and in what amounts. The results are compared against a predetermined cutoff value to determine if the result is positive or negative.

Why might I need a complete blood count (CBC) test as part of my routine care or diagnosis?

This test is typically ordered after a preliminary urine drug screen shows a positive result for barbiturates. It may be requested for various reasons including: monitoring patients on barbiturate prescriptions for compliance or misuse, workplace drug testing programs, legal or forensic investigations, pre-employment screening, or as part of a comprehensive drug testing panel. The confirmatory test provides legally defensible results because of its high accuracy and specificity.

What do the results of a complete blood count (CBC) test mean for your overall health?

Your test results will typically be reported as either 'Positive' or 'Negative' based on the established cutoff threshold. A positive result means barbiturates were detected in your urine at levels above the cutoff, indicating recent barbiturate use. A negative result means no barbiturates were detected, or levels were below the detectable threshold. It's important to discuss your results with your healthcare provider, who will consider your medical history, prescription medications, and the specific circumstances of the test when interpreting the results.

Reference range

Cutoff: 200 ng/mL or 300 ng/mL (laboratory-defined, per SAMHSA or institutional guidelines). Negative (not detected) below the assay cutoff; positive (detected) at or above the cutoff.N/A

Specimen: urine

No fasting required. Patients should be advised that certain prescription and over-the-counter medications may produce positive results. Inform the laboratory of all current medications at the time of collection.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

How long do barbiturates stay detectable in urine?

The detection window varies depending on the specific barbiturate, dosage, frequency of use, and individual metabolism. Short-acting barbiturates (like pentobarbital) may be detectable for 2-4 days, while long-acting ones (like phenobarbital) can be detected for up to 2-3 weeks after last use. Chronic use can extend detection times significantly.

Will a positive result mean I am abusing my medication?

Not necessarily. A positive result simply indicates the presence of barbiturates in your system. If you have a legitimate prescription for barbiturates, this is expected and appropriate. Your healthcare provider will interpret the result in context of your prescribed dosage and treatment plan. The confirmatory test helps distinguish between legitimate therapeutic use and misuse.

Can false positive results occur with this test?

The confirmatory method used (GC-MS or LC-MS/MS) is highly specific and greatly reduces the risk of false positives compared to initial screening tests. These methods can precisely identify individual barbiturate compounds, making false positive results extremely rare. However, it is important to disclose all medications and supplements you are taking to your healthcare provider for accurate interpretation.

Do I need to prepare for this test?

No special preparation is typically required. You should continue taking any prescribed medications as directed by your doctor. Inform the testing facility about all medications you are currently taking, including over-the-counter drugs and supplements. Bring a list of your current prescriptions if possible.

Who can see my test results?

Test results are protected health information and are shared only with authorized parties. These typically include your healthcare provider, the person or organization that ordered the test (such as your employer if part of a workplace testing program), and as required by law. The specific privacy practices should be explained to you before the test.

Sources

1
MedlinePlus - Drug TestingSource
2
Mayo Clinic Laboratories - Barbiturates Confirmation, UrineSource
3
LabCorp - Barbiturates, Quantitative, UrineSource

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