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HomeHealth TopicDiagnostics

These 10 Medications Can Cause a False Positive on Drug Tests

Amy B. Gragnolati, PharmD, BCPSKatie E. Golden, MD
Updated on January 4, 2024

Key takeaways:

  • Some medications can cause a false positive on a urine drug test. This means the test shows the presence of certain substances or medications you haven’t actually taken.

  • Antidepressants, decongestants, and dextromethorphan (Robitussin, Delsym) are examples of medications that can cause a false positive.

  • If you think you’ve had a false positive on a urine drug test, talk to your healthcare provider. They may be able to run a second test to confirm whether the results were inaccurate.

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A drug test can detect the presence of certain medications and substances in the body. The most common type of drug test is a urine test. 

Inaccurate results on drug tests can happen. For instance, a false positive is when a drug test shows the presence of a medication or substance that hasn’t been taken. But how does this happen?

Sometimes a false positive can be the result of a laboratory error. But, more often, medications are the cause of false positives. Below we'll review 10 medications that can have this effect. We’ll also cover how urine drug tests work and other products that may cause a false positive.

What’s a urine drug test?

Before we get into the medications that can cause a false positive, let’s discuss what a urine drug test is and why you might be asked to take one. Urine drug tests look for the presence of specific substances in the body. This includes prescription-only medications and certain illegal substances.

There are many scenarios in which might be asked to take a urine drug test, including:

  • You’re prescribed a controlled substance. Your healthcare provider may request a urine drug test if you're prescribed high-risk medications like opioids or benzodiazepines. This allows them to check for other substances that could be dangerous when combined with these medications. 

  • It’s part of a job interview process. You may be asked to complete a drug test as a condition of employment.

  • It’s an employer-mandated screening. Some employers may require their employees to complete drug tests every so often.

  • It’s part of a medical workup. A urine drug test can be part of a physical exam you receive in the ER. A drug test is also a common part of mental health evaluations.

GoodRx icon
  • What causes a false positive? Drug test results can be affected by medications and foods. Learn what a false positive test result means.

  • What about delta-8 THC? Delta-8 THC is a chemical in cannabis plants that’s used in manufactured cannabis products. Will it show up on a drug test?

  • Can you be tested for cannabis at work? Your employer may be able to make you take a marijuana drug test. It often depends on the state you live in.

What does a urine drug test look for?

Many urine drug tests check for the following medications and substances:

  • Tetrahydrocannabinol (THC), an active ingredient in cannabis

  • Prescription-only opiates and opioids like oxycodone (Roxicodone, Oxycontin) and morphine (MS Contin)

  • Illegal opiates and opioids like heroin

  • Phencyclidine (PCP)

  • Amphetamines like Adderall and illegal methamphetamine

  • Cocaine

  • Barbiturates like phenobarbital and butalbital

  • Benzodiazepines like alprazolam (Xanax) and lorazepam (Ativan)

Some urine drug tests screen for one specific medication or substance. These include drug tests that look for:

  • Tramadol (Qdolo, Conzip)

  • Methadone (Methadose)

  • Fentanyl 

  • Lysergic acid diethylamide (LSD) 

  • Methylenedioxymethamphetamine (MDMA), more commonly known as ecstasy

Medications that may cause false positives

Infographic showing the OTC and prescription medications that can cause false positives on drug tests.

1. Dextromethorphan (Robitussin, Delsym)

Dextromethorphan is the main ingredient in many over-the-counter (OTC) cough suppressants. If you’ve taken dextromethorphan, a urine test may show a false positive for PCP.

2. Diphenhydramine (Benadryl)

Diphenhydramine is an antihistamine that can help treat allergies, itching, and cold symptoms. Diphenhydramine may show up as a false positive for some opioids. But it’s not clear what dose of diphenhydramine would cause a false positive. Typical doses of diphenhydramine may not cause a false positive.

Some reports have also shown that diphenhydramine may result in a false positive for PCP. But this is likely rare.

3. Pseudoephedrine (Sudafed) 

Used to treat sinus and nasal congestion, pseudoephedrine may cause a false positive for amphetamines or methamphetamines.

4. Phentermine (Adipex-P)

Phentermine is FDA approved to help some people lose weight. Taking phentermine can cause false-positive urine test results for amphetamines.

5. NSAIDs like ibuprofen (Motrin, Advil) and naproxen (Aleve, Naprosyn)

Ibuprofen and naproxen are in a group of medications called nonsteroidal anti-inflammatory medications (NSAIDs). These medications help treat fever, inflammation, and pain. 

With ibuprofen and naproxen, there’s a small chance your urine test may show a false positive for barbiturates, a type of sedative, or THC. Another NSAID, oxaprozin (Daypro), may result in a false positive for benzodiazepines.

6. Some antidepressants like venlafaxine (Effexor XR) and sertraline (Zoloft)

Several antidepressants can cause false-positive urine drug test results. Examples include:

7. Quetiapine (Seroquel)

Atypical antipsychotics like quetiapine can help treat certain mental health conditions like bipolar disorder and schizophrenia. Quetiapine can cause a false positive for opioids (specifically methadone) on a urine drug test.

8. Proton pump inhibitors like pantoprazole (Protonix)

Proton pump inhibitors (PPIs) can treat gastroesophageal reflux disease (GERD) and heartburn symptoms. Taking PPIs — specifically pantoprazole — may cause false-positive urine drug test results for THC.

9. Quinolone antibiotics like levofloxacin (Levaquin) and ofloxacin

Quinolone antibiotics treat a variety of bacterial infections. Levofloxacin and ofloxacin are the most likely quinolone antibiotics to cause a false positive for opiates on a urine drug test. Ofloxacin may also cause a false positive for amphetamines or methamphetamines.

10. Promethazine

Promethazine is part of a group of medications called phenothiazines. It can be used to help relieve nausea and vomiting. But it can cause false-positive urine test results for amphetamines or methamphetamines.

Medications that can cause false positives in rare cases

Although rare, false-positive drug tests can be caused by a few other medications. These medications include labetalol (Trandate), doxylamine (Unisom), and tramadol.

Labetalol

Labetalol is part of a group of medications called beta-blockers. It’s used to lower blood pressure. While rare, labetalol may cause a false positive for amphetamines or methamphetamines.

Doxylamine

Doxylamine is an OTC medication that may help people who struggle to fall asleep at night. Large doses of doxylamine can cause a false positive for opioids (specifically methadone).

Tramadol

Tramadol is an opioid medication that treats pain. Large doses of tramadol can cause a false positive for methadone or PCP.

Debunked: Does methylphenidate cause a false positive for amphetamines?

Methylphenidate is a stimulant medication used to treat attention-deficit hyperactivity disorder (ADHD). Many sources state that methylphenidate can cause false positive results for amphetamines. But research shows this isn’t true. If you’re prescribed methylphenidate for ADHD, you shouldn’t have to worry about having a false positive for amphetamines.

What else, besides medications, can cause a false-positive drug test?

Products other than medications can cause a false-positive drug test. Examples include:

  • Poppy seeds: If you eat foods containing poppy seeds — like bagels, salad dressings, and crackers — it’s possible to get a false positive for codeine or morphine on a urine drug test. So it may be a good idea to avoid consuming poppy seeds for a couple days before a scheduled drug test. Though, the research in this area has looked at large quantities of poppy seeds, so it’s unclear if smaller amounts will cause a false positive.

  • CBD (cannabidiol) products: Some CBD products may contain THC. While not exactly a false positive, it’s good to keep in mind that these products may cause you to test positive for THC on a urine drug test.

  • Hemp products: Similar to CBD products, hemp products may contain varying amounts of THC. So it’s possible that hemp products, including teas and bars, could result in a positive for THC.

If you ingest any of the above products regularly, let your healthcare provider know before taking a drug test.

What should you do if you get a false positive on a drug test?

If you think you’ve had a false positive on a urine drug test, consider whether any medications you take could be responsible. Then, talk to your healthcare provider. They may be able to invalidate the results by running a second test. Confirmation tests check specifically for the substance or medication in question. And these tests are much less likely to show false positives.

In some cases, though, running a second test may not be possible. Talk to your provider if you’re concerned about a false positive on a urine drug test.

The bottom line

False positives on urine drug tests can happen. A false positive is when a drug test shows the presence of a medication or substance that hasn’t actually been taken. 

Multiple medications can cause false-positive drug tests. Some examples include ibuprofen (Advil, Motrin), dextromethorphan (Robitussin), and certain antidepressants, including sertraline (Zoloft). If you think your urine drug test results are inaccurate, talk to your healthcare provider. They may be able to perform a second test that’s more specific and accurate.

References

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Baron, J. M., et al. (2011). The trazodone metabolite meta-chlorophenylpiperazine can cause false-positive urine amphetamine immunoassay results. Journal of Analytical Toxicology

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