Instant Drug Tests: Not as Handy as They Seem

As an employer, you likely seek out solutions that combine time and cost-efficiency, plus convenience. It’s also key to make sure that all of your internal processes follow applicable laws — especially when it comes to your workplace drug testing.

If you have a drug testing program in place, you’ve probably heard of instant drug tests that seem ideal for pre-employment, reasonable suspicion, post-accident, and random drug testing. But did you know that instant tests actually run the risk of weeding out people who are not abusing drugs?

At Test Smartly Labs, we advocate the use of instant drug tests as screening tools to be used in conjunction with further testing when necessary. Here’s why we see instant drug tests as instant drug screens.

Why Instant Drug Tests Can’t Be Relied Upon

False Positives

As recently as 2010, instant drug tests produced false positives in 5 – 10% of cases. This means that if you only rely on an instant drug test, you could be turning away perfectly good applicants or employees based on incorrect information. A variety of substances can cause an applicant or employee to fail these instant drug screens, including:

  • 1 tsp of poppy seeds. Yes, that poppy seed bagel could cause you to fail your instant drug test by showing up positive for opioid abuse. The chemicals from the poppy seeds can stay in your system for 2-3 days.
  • Certain cold medications, antidepressants, and pain relievers. The medicine you take for your runny nose might trigger a false positive for amphetamines, along with certain antidepressants. Other antidepressants and painkillers can show false positives for benzodiazepine addiction. Ibuprofen use can lead to false positives for marijuana, benzodiazepines, or barbiturates.
  • Antibiotics. Are you on medication for an infection? If so, you might see false positive instant drug test results for opioids or marijuana use.
  • Diet pills or sleep aids. Taking a pill to aid in weight loss can translate to a false positive for amphetamines, while your sleep aids can show up as barbiturates.

False Negatives

False positives are bad enough — but instant drug screens also have instances of false negatives in 10 – 15% of cases! In particular, prescription drugs like OxyContin and Percocet and opioids like methadone and fentanyl are missed in instant tests. Sedatives and hypnotic drugs might be missed by instant tests, too.

False negatives occur often in instant urine tests because cutoff levels are not appropriate or sensitive enough. A trace of illegal substances may be present in someone’s system, yet below the cutoff level, resulting in a negative. A lab-based test is more sensitive and can detect lower substance levels, meaning there are fewer false negatives.


Depending on where you get your instant drug tests — and particularly if you order them from the internet — they may not produce legally admissible results. This means they probably won’t hold up in court should a former or prospective employee pursue legal action against your company due to their termination or failure to get the job.


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