False Positive Drug Test Results

While there are many instances that may lead to a false positive result, there are certain situations and products that are more common causes. Here are some of the top causes of false positive drug test results.

Antidepressants

There are certain antidepressants that may cause a false positive on a drug test. One of the most notable of these is sertraline (Zoloft) which may incorrectly indicate benzodiazepine metabolites.^[1]

Antipsychotic medication

There are several types of antipsychotic medications that can cause false positive results in drug tests. For instance, quetiapine which is used for schizophrenia and bipolar can show up as methadone in urine tests, and chlorpromazine can show up as amphetamines.^[1]

Other psychiatric medications 

The following medication may also cause a false positive result in standard drug tests:^[1]

• Clomipramine

• Amitriptyline

• Bupropion

• Trazodone

• Venlafaxine

• Hydroxyzine

• Haloperidol

• Sulpiride

• Perazine

• Levomepromazine

• Aripiprazole

• Risperidone

• Amisulpride

• Lamotrigine

• Carbamazepine

• Methylphenidate

• Atomoxetine

Antihistamines

Over-the-counter antihistamines designed to alleviate coughs, such as Benadryl, contain diphenhydramine. Despite its innocent nature, diphenhydramine may show up on drug tests as opioids, methadone, or even PCP.^[2]

HIV Medication

Antiretroviral drugs like efavirenz (Sustiva) are used to treat HIV infections. If you are using a home drug test kit and are also taking this medication, it may show that you have marijuana metabolites (cannabinoids) in your system. Lab drug tests are more sensitive and will be able to correctly distinguish the two substances.^[3]

Ibuprofen (NSAIDs)

Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen, have been shown to cause false positive results for barbiturates and cannabinoids. Ibuprofen has also been shown to cause false positive results for PCP in some immunoassays.^[4]

Weight loss pills

Many forms of diet pills, such as Phentermine, contain chemicals similar to amphetamines that suppress appetite. Diet pills may flag on a drug test screening for amphetamines such as meth, which could lead to a second test being required.

Secondhand Marijuana Smoke

THC is the chemical in marijuana that creates the high people feel when it is taken. If you are with someone who is smoking marijuana, inhaling it can cause THC to appear in your system even if you haven’t directly taken it. However, it would require a large amount of secondhand marijuana smoke to yield a false positive result, as most cut-off points will account for this.

Poppy seeds

The small black seeds commonly found on bagels and other food products are from the poppy plant, the same plant from which opioids such as codeine and morphine are derived. More modern drug screenings will often have a high enough cut-off point to avoid poppy seeds causing false positives, though some labs may still use older tests.

Mouthwash

While screening for alcohol in drug tests is relatively uncommon, certain ethanol-based products may cause a false positive if used regularly. Ethanol products that can affect alcohol tests include mouthwash, liquid medications, vanilla extract, or even hand sanitizers. 

CBD products

CBD (cannabidiol) products have boomed in popularity in the last decade, with CBD drinks, oil, chocolate, and other edibles being widely available. As CBD is derived from hemp, a relative of the cannabis plant, some companies add trace amounts (up to 5%) of THC to their products to boost their relaxing effects. This can cause some urine drug tests to show traces of THC, though the cut-off point for most modern drug tests will not cause a false positive for CBD.

Coca tea

Coca tea is a popular health remedy in Peru and other parts of South America. It is made from the same leaf as cocaine and contains the same metabolites. Coca leaves in any form are illegal in the US, though it may show up in drug tests if a person has consumed coca tea while south of the border.