Cross Reaction Search
Choose from the menus below to determine which drugs may result in a positive cross-reaction for another drug.

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Drug Detection Times in Urine

Drug/IdentifierMinimumMaximumCut-Off Level
Marijuana (THC)†2 hoursUp to 40+ days50 ng/ml
Cocaine (COC) †1-4 hours2-4 days300 ng/ml
Methamphetamine (METH) †2-7 hours2-4 days1000 ng/ml
Amphetamines (AMP) †2-7 hours2-4 days1000 ng/ml
Ecstasy (MDMA) †2-7 hours2-4 days500 ng/ml
Opiates (OPI) †2 hours2-3 days2000 ng/ml
Phencyclidine (PCP) †4-6 hours7-14 days25 ng/ml
Benzodiazepines (BZO)2-7 hours1-4 days300 ng/ml
Methadone (MTD)3-8 hours1-3 days300 ng/ml
Barbiturates (BAR)2-4 hours1-3 weeks300 ng/ml
Tricyclic Antidepressants (TCA)8-12 hours2-7 days1000 ng/ml
Oxycodone (OXY)1-3 hours1-2 days100 ng/ml

† The Substance Abuse and Mental Health Services Agency (SAMHSA), has set "cut-off" levels when testing for marijuana, cocaine, methamphetamine, amphetamines, ecstasy, opiates, and PCP. First Check is manufactured to conform to those standards. Screening tests may not detect amounts of drugs in a urine sample that are below the cut-off level. Even though some level of drug may be present in a urine sample, the sample would still be considered Negative Result if the drug level is below the cut-off level.


First Check wants to ensure that you have a place to find the answers to all your questions in the privacy of your home.  Here you will be able to find details on the 12 most commonly abused drugs including:

  • Drug Lookup- Information on the 7 Illicit & 5 Prescription Drugs most commonly abused
  • Slang Lookup- Street terms used for different types of illict and prescription drugs
  • Drug Cross Reaction Lookup- medication that might interact with a First Check® Drug Test
  • Drug Detection & Cut-off Levels- The nanogram cut-off levels and detection times for      each drug of the 12 drugs tested for in a First Check® Home Drug Test