When taking a drug test, most people only consider the possibility of a positive or negative result. There is the possibility of a third result: an inconclusive drug test. Inconclusive drug test results can happen for many reasons, either accidentally or intentionally, that can call the results into question. This is not the same as a positive or negative result, which represents the presence or lack of drugs.

Does this result indicate a failed drug test? In short: it is not a failure, but it’s not a success either. An inconclusive drug test represents a sample that was unable to reliably test as positive or negative. Drug tests involve complex chemistry, and any number of real-world complications can render those results invalid or otherwise inconclusive. Inconclusive results almost always require the test to be retaken. Today we’ll take a closer look at three things that might cause an inconclusive drug test to happen.

Why Would a Test Come Back Inconclusive?

A drug test can typically become inconclusive for one of three reasons: internal adulteration, external adulteration, or on-site technician error. These are the most common reasons for inconclusive results.

An internal adulteration is a situation where the sample (typically urine) has been overly diluted. Typically this requires drinking a large amount of water or other liquid before testing to increase urine volume. This can produce inaccurate results that will render the drug test inconclusive. There are lab methods that can determine if samples were diluted either before or after collection.

External adulteration is a situation when something additional has been added to the sample. Most often external substances are added when the patient is not being observed to try to throw off the results. These are typically added to throw off the analytic chemistry results of the drug test. This will not result in a negative test though, only an inconclusive one, and necessitate retesting.

Most labs have effective practices in place to minimize the possibility of human error in handling samples. However, there’s still the possibility of improper storage or delayed testing that can cause a sample to become inconclusive. Like any other inconclusive result, the easiest way to resolve this is to retake the drug test.

How Common Is An Inconclusive Drug Test?

Just how common are inconclusive drug tests? They happen more frequently than you might expect, but are still not so uncommon as to be unusual. Whether for accidental or purposeful reasons, there are multiple possibilities a drug test might come back inconclusive. A Medical Review Officer (MRO) will typically look over inconclusive results to see possible reasons for it. The MRO will also frequently request a retest for inconclusive results. Usually, a retest is all it takes to make an inconclusive drug test result in a positive or negative one.

Remember, this result is not a sign of a potential positive or negative, simply that the result is not conclusive. It’s also not a sign that there was any intentional misleading of the test either. Accidental mishandling on the patient’s part during collection is always a possibility. There is potential for lab error for an accidentally inconclusive result. Multiple inconclusive tests in a row might be seen as suspicious, however, or at minimum require further inquiry.

The best way to avoid drug test results like this is by taking the test legitimately. Any legitimate screening service is interested in making minimizing inconclusive results a priority and giving accurate results for employers. Soteria Screening Laboratories has experience dealing with different types of drug tests, including hair, saliva, and urine. They provide screenings for a range of drug tests, including alcohol, nicotine, marijuana, opioids, and other drugs. Contact them for more information or to schedule a test or screening