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Test Code THCUM Carboxy-Tetrahydrocannabinol (THC) Confirmation, Urine

Important Note

This test is for confirmation testing only. For screening purposes please order a Rapid Drug Screen, Urine LAB676 first before this test.

Additional Codes







Reporting Name

Carboxy-THC Confirmation, U

Useful For

Detection and confirmation of drug abuse involving delta-9-tetrahydrocannabinol (marijuana)

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type


Specimen Required

Collection Container Tube: Plastic urine container

Submission Container/Tube: Plastic, 60-mL urine bottle

Specimen Volume: 20 mL

Collection Instructions:

1. Collect a random urine specimen.

2. Submit 20 mL in 1 plastic bottle.

3. No preservative.

Additional Information:

1. No specimen substitutions.

2. No STATS are accepted for this procedure.

3. For situations where chain of custody is required, a Chain-of-Custody Kit (T282) is available. For chain-of-custody testing, order THCX / Carboxy-THC Confirmation, Chain of Custody, Urine.

4. Additional drug panels and specific requests are available. Call Mayo Medical Laboratories at 800-533-1710 or 507-266-5700.

5. If urine creatinine is required or adulteration of the sample is suspected, the following test should be requested, ADULT / Adulterants Survey, Urine. For additional information, please refer to ADULT / Adulterants Survey, Urine.

6. Submitting less than 20 mL will compromise our ability to perform all necessary testing.

Specimen Minimum Volume

5 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Refrigerated (preferred) 14 days
  Frozen  14 days
  Ambient  72 hours

Reference Values



Cutoff concentration:

Carboxy-THC- by GC/MS <3.0 ng/mL

Day(s) and Time(s) Performed

Monday through Friday

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information


G0480 (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
THCU Carboxy-THC Confirmation, U 20521-1


Result ID Test Result Name Result LOINC Value
2497 Carboxy-THC- by GC/MS 20521-1
21186 Carboxy-THC Interpretation 69050-3
21187 Chain of Custody No LOINC Needed

Analytic Time

2 days

Reject Due To


Mild OK; Gross OK




Mild OK; Gross OK



Method Name

Gas Chromatography-Mass Spectrometry (GC-MS) Confirmation with Quantitation