Health Encyclopedia

Tricyclic Antidepressant Screen

Does this test have other names?

Tricyclic antidepressant (TCA) testing

What is this test?

This test is used to check a sample of blood or urine for tricyclic antidepressants (TCAs). Healthcare providers prescribe these medicines for depression and a number of other problems. These include anxiety, headaches, and nerve-related pain.

These medicines can be helpful in normal doses. But taking too much can be fatal. These medicines are often the cause of death in prescription-medicine overdoses in the U.S. 

Why do I need this test?

You might have this test to help your healthcare provider prescribe the proper dose of a TCA. Healthcare providers may also do this test if you have symptoms that may point to taking too much of one of these medicines.

Symptoms of overdose include:

  • Sedation

  • Difficulty thinking

  • Hallucinations

  • Serious changes in heart rhythm

  • Low blood pressure

  • Seizures

  • Body temperature that is too high (hyperthermia)

  • Dilated pupils

What other tests might I have along with this test?

If your healthcare provider suspects that you have taken too much of one of these medicines, he or she may do an electrocardiogram to check your heart's rhythm. Your provider may also order other blood tests. These include a complete blood count, creatinine, electrolytes, and blood sugar. He or she will also check for other substances that are commonly taken along with a TCA overdose. 

What do my test results mean?

A result for a lab test may be affected by many things, including the method the laboratory uses to do the test. If your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your healthcare provider.

Depending on the tricyclic antidepressant medicine you are taking, the level for treatment will range from 50 to 250 nanograms per milliliter (ng/mL). Toxic levels are above 300 to 500 ng/mL.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm, or a urine sample, which is usually provided by urinating into a cup. The result of a urine test for TCAs will be reported only as negative or positive.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.  

What might affect my test results?

Some other medicines can interfere with this test, causing a false-positive for TCAs. These include carbamazepine, quetiapine, diphenhydramine, thioridazine, chlorpromazine, and cyclobenzaprine.

How do I get ready for this test?

Tell your healthcare provider about any other medicines you have taken recently. 

Medical Reviewers:

  • Turley, Ray, BSN, MSN
  • Ziegler, Olivia Walton, MS, PA-C