Tricyclic Antidepressant (TCA) Screen
Reviewed
Also called: TCA test, TCA screen, Tricyclic Screen
This test checks whether tricyclic antidepressants (TCA) are present in your blood or urine and can measure the amount. It is used to help find the right dose, detect misuse, or diagnose a TCA overdose. TCAs are prescription antidepressants that can cause dangerous side effects if levels are too high.
Specimen: Blood or urine
Urgent safety information
If you have symptoms of a TCA overdose (dry mouth, blurred vision, constipation, trouble urinating, drowsiness, lightheadedness, seizures, confusion, tremors), call 911 or go to the nearest emergency center immediately.
Why this test may be ordered
- To help your provider prescribe the right dose of a TCA.
- To find out if you are misusing TCA (taking it without a prescription or taking more than the prescribed dose).
- To diagnose a TCA overdose.
- May be part of a drug (toxicology) screen.
Preparation and collection
No special preparation needed.
Blood draw from a vein in your arm or urine sample in a sterile cup.
Blood test: There is very little risk. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly. Urine test: There is no known risk.
Understanding results
TCA screen results can be obtained from blood or urine. Blood results show the level of TCA in your bloodstream. Urine results may be qualitative (detected/not detected) or quantitative (level). Your healthcare provider will interpret the results.
- Therapeutic level (quantitative blood result): The level of TCA in your blood is within the expected safe and effective range for your prescribed dose. Limitation: A level that is safe for one person may be dangerous for another; always discuss with your provider. Next step: Continue taking your medication as prescribed. Your provider may adjust your dose based on the level.
- Dangerously high level (quantitative blood or urine result): The level of TCA in your blood or urine is dangerously high, suggesting an overdose. Limitation: This indicates a medical emergency; prompt treatment can be lifesaving. Next step: Call 911 or go to the nearest emergency center immediately.
- Screen positive (qualitative urine result): TCA was detected in your urine, but the amount is not known. Limitation: A positive result does not measure the amount. The level could be low, safe, or dangerous. Next step: Your provider may order a quantitative test to check the amount. If you have overdose symptoms, seek emergency care now.
- Screen negative (qualitative urine result): No TCA was detected in your urine. Limitation: A negative result does not completely rule out TCA use if the test was done too soon after taking the medication. Next step: If you take a prescribed TCA and the result is negative, discuss with your provider. No further action if not taking TCAs.
- Blood test: There is very little risk. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
- Urine test: There is no known risk.
- Results are interpreted by a healthcare professional; reference intervals depend on the specific TCA and clinical context.
What to do next
Results should be discussed with your healthcare provider. If you have symptoms of a TCA overdose, call 911 or go to the nearest emergency center immediately.
- What is a tricyclic antidepressant (TCA) screen?
- Why do I need a TCA screen?
- What happens during a TCA screen?
- Will I need to do anything to prepare for the test?
- Are there any risks to the test? What do the results mean?
Evidence source
U.S. National Library of Medicine: Tricyclic Antidepressant (TCA) Screen