How the First Check® Home Drug Test works


The First Check® Home Drug Test Thin Layer Chromatography process takes place on each of the test strips on the Test Lid. The process works by exposing the urine sample to special chemical reagents within the test strip in a specific order and at a specific speed.


  • When the First Check® Test Lid is secured to the top of the cup and the cup is tilted into its legs, the urine in the cup comes into contact with the First Check test strips on the Test Lid.
  • The absorbent material of each test strip carries the urine sample across the strip at a specific speed.
  • First, the urine sample encounters special molecules and carries them further up the test strip where they will interact with drug-specific antibodies that only react to metabolites for the specific drug being tested.
  • If the urine sample does not contain the specific drug metabolites being tested for, the special molecules react with the antibodies to turn a color.
  • When the molecules turn color, the test is Negative for the drug being tested for.
  • If the urine sample does contain the specific drug metabolites being tested for, the molecules do not turn color.
  • When the molecules do not turn color, this indicates a Preliminary Positive Result for the drug being tested for.
  • Finally, the sample reaches the Control Line at the top of the test strip where a reagent makes the molecules turn color to indicate that the test is working properly.
  • When the Control Line turns color, it means the test is working properly.

The First Check® Home Drug Test is considered a “screening test.” First Check recommends all Preliminary Positive Results be sent to our laboratory for free confidential confirmatory testing. Gas chromatography/mass spectrometry (GC/MS) is considered the gold standard in laboratory testing for most drugs.
First Check customers who have received a Preliminary Positive Result can use the Pre-addressed Mailing Box included in the First Check Home Drug Test kit to send the urine sample to the lab for free confidential analysis. The First Check Lab is one of the nation's premier forensic drug testing facilities that uses the most advanced processes and equipment, offering expert toxicological review to produce the most accurate result possible – all while maintaining strict confidentiality.
Click here to learn more about how to use the test.