Urine Toxicology Pearls


Drug seekers will love this post.

EMedHome.com recently published a set of pearls about urine drug testing that included several things I wasn’t aware of.

Did you know that …

  • Urine levels of “ecstasy” (MDMA) need to be quite high before they will be picked up by the urine drug screen since the tests have a low sensitivity for MDMA?
  • Zantac, Prozac, and labetolol can all cause false positive results for amphetamines?
  • Zoloft and Daypro can cause false positive drug screens for benzodiazepines?
  • Several benzodiazepines are difficult to detect on urine drug screens – including Librium and Versed?
  • Levaquin, Cipro, dextromethorphan (common in OTC cough meds), rifampin, and verapamil can all cause false positive tests for opiates?
  • Standard urine toxicology screens do not usually detect Vicodin, Tramadol, Fentanyl and Percocet?
  • Ingestion of one poppy seed bagel can cause a false positive opiate test?
  • Most drugs are undetectable 3 days after use?

Links to some of the cited articles are here, here, and here.

By the way … if you came across this post in a web search on how to beat drug tests and now think you’ve got it made – don’t worry. There are plenty of other ways that doctors can tell whether or not you’re using drugs.

I’m not giving away all of our secrets.


  1. Pharmacist Adam on

    Efavirenz (Sustiva and Atripla-HIV drugs) can cause false-positive marijuana and benzodiazepine test results, which has been problematic in some prisons where prisoners have lost good behavior time and been thrown in solitary confinement over the issue.

  2. Test for Tylenol. That should give a fairly good indication of recent,common opioid, prescription abuse; or how screwed your liver is.

  3. let me go get my popcorn and wait for this thread to get interesting as there are a few things posted there that just are not EXACTLY true (eg the poppy seed bagel thing has not been true since the threshold for reporting on most standard tests has been raised such that poppyseeds won’t trigger a positive).

  4. This is timely!

    I was just remembering the Seinfeld episode where Elaine had been eating poppy seed bagels and so her boss thought she was on heroin. Funny episode! 🙂

  5. Yep, I was on Cymbalta and Prilosec and popped positive on a urine screen for every drug known to man. Not a good day for me.

  6. Ahhh…but most of the VA clinics now specifically screen for oxycodone and suchlike…..also, if you come up positive for something you aren’t taking on a rapid screen, request a send-out.

  7. Carol, thanks for the heads-up. Did you know that Cymbalta is also prescribed under the name Yentreve for people WITH urinary problems? I’m not surprised it shows up on tests.

  8. “Ingestion of one poppy seed bagel can cause a false positive opiate test?”

    The federal guidelines say that when testing for opiates, a “postive” is one that is more than, say, 25. However, not all states use the federal guidelines. Michigan is a case in point, this happened to a coworker’s son. Son admitted to a crime and was subjected to random urine testing while on probation.

    The son ate a poppy seed bagel the day before he was randomly urine tested. He scored a 3 for opiates. Because Michigan does not use federal guidelines the prosecutor wanted him to go to jail…for eating a bagel.

    Talk about a backwards state!

    Now I do know there are some poppies that do not produce opiates, and some that do. Only the poppies that produce opiates are illegal to grow in Michigan.

  9. After much begging and pleading, the son was given further probation instead, thus adding a crime to his record (consuming opiates). But no jail time was involved. Apparently, Michigan legal rules say the judge cannot overrule the prosecutor’s stupidity.

  10. Had a pregnant patient have a false-positive for amphetamines – she was on Zantac, which we initially suspected, but turns out she wasn’t taking it. It was methyldopa (old-time antihypertensive only really used in pregnancy) – apparently this wasn’t the first time the clinic had seen that.

    I have had issues with fentanyl not popping up – when it most definitely should have.

    • I had an ER visit last month for chest pains. Dr. did a drug test. I tested positive for amphetamines. I only take methyldopa and prenatal vitamins. Have since followed up with family dr. Still testing positive. Dr. says there’s not way it’s the methyldopa. What can I do?

      • I just had a positive result for amphetamines but I also only take methyldopa and prenatals. I told the Dr it has to be a false positive…he says no way…. what to do???

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  12. This why when I give drug screens for people I have under probation, I give them a list of stuff that could come up as false positive. Some of the medicines like anitdepressants, I will ask to see a Dr. Prescribtion beforehand, but should anything else come up and they claim for example it was poppy seeds, I violate them. They were warned from the beginning.

  13. when given a confirmation test for popping positive for cocaine, will other drugs, if taken, show up or do they only test for the drug you popped positive for and the amounts of it, if any and isnt a false positive like I believe mine was, should I ask for a confirmation test? I hadnt used cocaine in 4 weeks but I have lupus, Im just wondering if the confirmation test will show everything in your system or are they specifically looking for the drug you popped positive for?

  14. My son in law lost his job because of a positive urine test. He claims it was due to his drinking tonic water and taking ibuprofen. Is this possible?

  15. I work in a Tox confirmation lab that uses LCMSMS to test urine drug screens. In office dips and semiquant immunoassay screens are notorious for false positive AND false negatives. LCMSMS is VERY hard to beat and has a 1/1,000,000 chance of cross reactivity. If your docs are smart, and I realize that not all are, they are hopefully sending out for LCMSMS confirmation of all positives and relevant negatives. This can alleviate MOST of the issue mentioned in this thread.

    • Thanks for this information.
      Two points and a couple of questions.
      First, if we order the tests, we’re using the information to make treatment decisions immediately. We infrequently order send-out testing in the ED since it doesn’t affect how we will treat the patient. POCT or rapid lab turnaround is essential.
      Second, in many cases the hospital eats the cost of testing – especially now with the upgraded insurance plans that have been forced upon many patients.
      How much does LCMSMS cost and what is the turnaround time for typical testing? No need for specifics – just looking for ballpark answers.
      Also, just out of curiosity, what are your lab’s typical clients? I’m betting it is more law enforcement and employers and much less hospitals/medical offices.

      • While I agree that POCT testing can be an essential clinical tool, I believe that most clinicians are unaware of the limitations of this type of testing. At least that has been my experience. For instance, I have one pain mgmt office that reports a positive morphine on EVERY sample. Every sample. This does not seem to concern them at all. Obviously, they are not reading the results accurately or in a timely manner.

        Turnaround time is typically 24hrs and cost for LCMSMS screening varies from lab to lab, but ballpark $400-$800 depending on the number of drugs/medications being confirmed and price does varies from lab to lab. Our lab does a very conservative confirmation screen, but I know that some labs do not. The majority of our clients are medical offices (primarily pain mgt and OBGYN), but we also have many rehabs/sober living/halfway house that we test for as well.

      • I have worked with the Medtox Scan as a rapid test for UDS. We always report out presumptive positive as we know and understand that the test we use in the Laboratory is just a screening test. We inform the providers that if they want the confirmation test it can be added per their request.

        I have worked with Medtox in the past and now they fall under the umbrella of LabCorp. However, back then the confirmation test we were being charged $35 per analyte.

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