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Antidepressants Blood Test

Last updated Jan. 15, 2019

Approved by: Maulik P. Purohit MD, MPH

Carsten Schertzer

The Antidepressants Blood Test helps determine the levels of antidepressants in blood. It is used when adjusting the initial dose, and to ensure that antidepressant levels stay within an acceptable range.

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

  • Antidepressant Levels Blood Test
  • Antidepressant Medications Levels Blood Test

What is Antidepressants Blood Test? (Background Information)

  • Depression is a mental disorder characterized by a low state of mood, gloominess, and suicidal thoughts. Antidepressant medications treat depression
  • The main antidepressant medications are monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs), and selective serotonin reuptake inhibitors (SSRIs). They work by increasing concentrations of pleasure-provoking chemical messengers, called neurotransmitters
  • Three neurotransmitters in particular - dopamine, noradrenaline, and serotonin - belong to a class of monoamines. They are released by neurons as part of the “reward response”
  • Antidepressants may stimulate the release of monoamine neurotransmitters, elevating the mood. They also prevent the reuptake of monoamines by the monoamine transporter, causing levels to remain high
  • MAOIs inhibit the monoamine oxidase enzyme, which is responsible for degrading monoamines. This causes monoamines to remain for longer periods, elevating mood. MAOIs have a shorter half-life than both TCA and SSRIs
  • TCAs bock reuptake of the neurotransmitters serotonin and norepinephrine. TCAs reach maximal blood concentration in 1-3 hours and circulate for up to 2 days
  • SSRIs block reuptake of serotonin. Compared to MAOIs and TCAs, SSRIs are more specific for serotonin and generate fewer unwanted side reactions
  • The Antidepressants Blood Test helps determine the levels of antidepressants in blood. It is used when adjusting the initial dose, and to ensure that antidepressant levels stay within an acceptable range

What are the Clinical Indications for performing the Antidepressants Blood Test?

The clinical indications for performing the Antidepressants Blood Test include monitoring antidepressant therapy.

How is the Specimen Collected for Antidepressants Blood Test?

Following is the specimen collection process for Antidepressants 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 Antidepressants Blood Test Result?

The significance of the Antidepressants Blood Test result is explained:

  • A high test value may indicate antidepressant toxicity, which is marked by:
    • Fatigue
    • Nausea
    • Vomiting
    • Diarrhea
    • Altered mental status
    • Abnormal heart rate
    • Abnormal breathing
  • A low test value may indicate more antidepressant 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:

  • Depression is difficult to diagnose because there are currently no reliable laboratory tests available. Diagnosis relies entirely on clinical symptoms and information obtained from the individual’s friends and family

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.

The following DoveMed website links are some useful resources for additional information:





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: Oct. 31, 2015
Last updated: Jan. 15, 2019