Negative Dilute – Now What?

(February 2021) Negative Dilute – is that a drug test result that has sent you scrambling to the internet to try to interpret and come up with a response?  Well, let’s define the meaning of this test result and examine best practices for taking action as part of your drug-free workplace (DFWP) program.

What does it mean?

A good place to start is by unraveling the terms.  First, “negative” means that the panel of drugs tested for was not detected in the sample at the established cut-off levels.  Next, “dilute” indicates the concentration of the specimen was not typical – specifically, that the levels of creatinine (a waste product produced by the body) in the urine and specific gravity (i.e., the density or concentration of the urine) were abnormal.  So, in short, a negative dilute result means that the donor was exceptionally hydrated at the time of the test; and the urine, and everything else it contained, was diluted.

What’s tricky with a negative dilute test result is that it’s unknown why the concentration of the specimen was dilute.  It may be totally innocent on the part of the employee or it could be they were attempting to disguise drug use by intentionally flooding their system with water.

It may be tempting to jump to conclusions about the donor’s intentions and actions leading up to the test.  But, with an eye on both fairness and objectivity, the caution here is to take a deep breath and not make assumptions.

What are the causes?

There are several possible causes for a urine sample to become diluted.  Among these are

• Being overly hydrated, which comes down to drinking excessive water. Some people may do this as part of a healthy lifestyle, and others may do so to prepare for giving a urine sample, especially if they’ve had difficulties providing a sample in the past.
• Secondly, the individual may have health problems involving the kidneys which can result in a release of too much water in the urine.
• Also, some prescription medications have a diuretic effect, increasing urine production and the possibility of a diluted urine result.
• And, unfortunately, individuals may purposefully overhydrate in an attempt to beat the test.

Possible responses?

So, how do you as an employer with a DFWP program respond to a negative dilute result?  Start by checking your DFWP policy.  What direction or guidance does your policy provide?  If none is given, a good model to follow, even if you are not mandated to, is the Department of Transportation’s (DOT) guidelines for handling a negative dilute result.  DOT gives employers the option of either treating the result as a negative or requiring that the employee submit another urine specimen.

What you decide can vary based on the type of test administered – such as pre-employment, post-accident, random, reasonable suspicion, return-to-duty – but DOT requires that you treat each type of test the same.  For example, let’s say you sent an employee for a random test and received a negative dilute result.  If you require the employee to retest, then you have to do the same for the next person who tests negative dilute on a random test.

As part of responding to a negative dilute result, it’s always wise to contact the Medical Review Officer (MRO) who reviewed the test to determine if he/she has any other directions or guidance for you to consider.  Based on the creatinine concentration of the specimen, the MRO may request the employee take a second test in the same manner as the first or they may request recollection under direct observation.

According to DOT, only one recollection is allowed, and the second collection becomes the recorded result – even if it is another negative dilute.  In other words, you are not permitted to require the employee to take an additional test.

Tips to Help Avoid Negative Dilute Results

To prevent or reduce instances of diluted test results, share the following tips with your employees to help them prepare for testing:

• Limit excessive fluid intake before the test to prevent possible retesting.
• Avoid diuretics, like coffee and tea, at least two hours before giving a sample.

And keep these suggestions in mind as you administer your DFWP program:

• If you have employees who work in extreme conditions, like outside in hot summer heat, a best practice is to schedule drug testing early in their shift before they have consumed lots of liquids.
• Schedule random drug testing so that employees cannot plan to dilute their sample.
• If you do get a negative dilute result and are going to require the employee to give another specimen, be sure they go immediately to the collection facility after you notify them that they need to go. You might also want to consider transporting them to the facility to minimize their opportunity to drink excess fluids.

Of course, it’s always helpful if your DFWP policy includes information about how you’ll handle these types of situations should they happen.  It’s just smart business to have established rules that provide sound guidance and consistent practice.  Give Working Partners® a call to help clarify and articulate in writing how you’ll handle these and other not-so-common DFWP issues.