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Clozapine Level Blood Test

Last updated March 18, 2018

Approved by: Krish Tangella MD, MBA, FCAP

The Clozapine Level Blood Test assesses the levels of clozapine in blood. It is used when adjusting the initial dose and to ensure that clozapine levels stay within an acceptable range

What are the other Names for this Test? (Equivalent Terms)

  • Clopine Blood Test
  • Versacloz Blood Test
  • Zaponex Blood Test

What is Clozapine Level Blood Test? (Background Information)

  • Clozapine is an antipsychotic drug used to treat schizophrenia and bipolar disorder
    • Schizophrenia is a complex mental disorder characterized by hallucinations, social withdrawal, and extreme agitation
    • Bipolar disorder is characterized by bouts of either extreme depression or mania, lasting anywhere from several days to years. The cause of this condition remains largely unknown, though genetic associations have been identified
  • Clozapine is believed to work by altering the effectiveness of the brain chemicals dopamine and serotonin. However, the exact functioning mechanism is unknown
  • Like every other drug, clozapine must be kept within a certain range to prevent unwanted effects. If levels are too high, toxicity may result; if levels are too low, the drug may not successfully treat the condition
  • The Clozapine Level Blood Test assesses the levels of clozapine in blood. It is used when adjusting the initial dose and to ensure that clozapine levels stay within an acceptable range

What are the Clinical Indications for performing the Clozapine Level Blood Test?

The clinical indications for performing a Clozapine Level Blood Test include monitoring clozapine therapy.

How is the Specimen Collected for Clozapine Level Blood Test?

Following is the specimen collection process for Clozapine Level Blood Test:

Sample required: Blood

Process of obtaining blood sample in adults:

  • A band is wrapped around the arm, 3-4 inches above the collection site (superficial vein that lies within the elbow pit)
  • The site is cleaned with 70% alcohol in an outward spiral, away from the zone of needle insertion
  • The needle cap is removed and is held in line with the vein, pulling the skin tight
  • With a small and quick thrust, the vein is penetrated using the needle
  • The required amount of blood sample is collected by pulling the plunger of the syringe out slowly
  • The wrap band is removed, gauze is placed on the collection site, and the needle is removed
  • The blood is immediately transferred into the blood container, which has the appropriate preservative/clot activator/anti-coagulant
  • The syringe and the needle are disposed into the appropriate “sharp container” for safe and hygienic disposal

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the Clozapine Level Blood Test Result?

The significance of the Clozapine Level Blood Test is explained:

  • Excessive clozapine levels may indicate clozapine toxicity, which is marked by:
    • Drowsiness
    • Stupor
    • Dizziness, confusion
    • Nausea, vomiting
    • Anxiety
  • Low clozapine levels may indicate that more clozapine is necessary to achieve a therapeutic dose

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Clozapine is mainly used when more classical schizophrenia and bipolar disorder medications, such as haloperidol, cannot be used
  • Schizophrenia is strongly associated with suicidal thoughts and tendencies. Individuals exhibiting these tendencies should contact a healthcare professional immediately
  • Schizophrenia affects roughly 3 million persons in the US, or 1% of the population

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

Please visit our Laboratory Procedures Center for more physician-approved health information:


References and Information Sources used for the Article:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Sept. 4, 2015
Last updated: March 18, 2018