Dilute Specimen in Layman’s Terms

All the articles on the internet defining a dilute specimen were very technical and quite confusing for the average employer; hopefully you’ll find this description helpful.

When you receive a dilute drug test result (usually negative) it means the donor drank an excessive amount of liquids prior to taking the test. That happens for 2 reasons:

  1. They naturally just consume lots of liquids.


  1. They know it’s very difficult (but not impossible) for a laboratory to report a positive if the specimen is dilute; therefore may try and “dilute” their specimens before submitting it in an attempt to defraud the test.

What’s an employer to do?

That depends on your policy regarding dilute specimens. If you do not have a policy that addresses dilute specimens then you should consider writing one.

Most First Choice Drug Testing clients accept dilutes and do not re-test; however a few do require re-testing. Those that re-test in a NON-DOT setting inform the donor they do not accept dilute test results and take adverse action if the second test is also dilute.

According to DOT regulation (the gold standard of drug testing) if you do choose to recollect for dilutes and the second specimen is also dilute then the employer must accept those test results with no further testing. If considering creating a dilute policy for your NON-DOT applicant/employees the recommendation would be to follow DOT guidelines.

My suggestion for your NON-DOT applicant/employees: Re-collect all dilutes but do so unannounced. Explain to the applicant/employee that the test results were dilute, show them your policy regarding dilutes, and ask them for an explanation as to why their specimen was reported dilute. Inform them they will be required to re-test right away with a supervisor escorting them to the collection site. Based on the donor’s reaction to this intervention you should be able to quickly determine if the first dilute was an attempt to defraud the test.

Tim Zimmerman, President

First Choice Drug Testing