False Positive Drug Test: What Does It Mean For You?

False Positive Drug Test: What Does It Mean For You?


Drug testing is getting increasingly popular in the workplace in order to ensure safe work environment, improve employee productivity and decrease absenteeism, to keep health insurance costs down.  US government mandates drug testing in railroad, trucking, pipeline, airline, mass transit and shipping industries.

A positive drug test could lead to termination of working employees as well as newly hired job candidates.

Drug testings have also become more common in schools where students participate in extracurricular activities.

A false positive drug test signifies that the test has detected the presence of legal or illegal substances in the body system despite not consuming them.  Foods, drugs and other substances could cause false positives.

Most common substances tested are:

  • MMJ
  • Cocaine
  • 6-MAM and other opiates
  • Anabolic steroid Abuse
  • Methamphetamine
  • Prescription medications like stimulants, sedatives, tranquilizer or analgesics used for nonmedical reasons

Other substances that may be tested are:

  • Heavy alcohol use
  • PCP (phencyclidine)
  • Hallucinogenic drugs (LSD, mescaline, peyote, psilocybin, and ecstasy)
  • Inhalants (fumes/gases that are inhaled to produce intoxication such as aerosols, glues, nitrous oxide, butane, ether, and solvents)

Types of Drug Tests

  • Urine:  Urine testing is a very commonly used type of test.  It is simple, noninvasive, and highly accurate.  It normally tests for MMJ, cocaine, opiates, PCP, and amphetamines.  Immunoassay screening detects the parent drug and/or its metabolites and the amount of drug present above a predetermined cutoff concentration.  Gas chromatography/mass spectrometry or high-performance liquid chromatography is employed to obtain more precise results.  Urine drug test has high specificity, and by and large used to detect the presence of a specific drug when necessary.
  • Hair:  Hair testings are less liable to adulteration than urine tests.  Hair specimen renders a semi-permanent record of drug use.  Drugs circulating throughout the body system cling to the hair as it grows.  Therefore, if any drug was ingested recently, it will be found in the hairs near the scalp.  If one has taken drug in the past, the drug can be found in hair that has grown out.  The advantage of hair testing is that it can detect drug use over longer periods of time (usually around 90 days).
  • Sweat:  In this type of testing, bandage-like patches are placed on the skin to collect sweat to evaluate for drugs.  To avoid tampering, the adhesive plastic film cannot be reapplied once removed.  This is not a widely used method due to compliance issues.
  • Blood:  Blood tests are the most accurate testing method and measure the actual amount of alcohol or other drugs in the blood.
  • Saliva:  A saliva test is used for detection of drugs consumed within the past few days.  This method can detect illicit substances like 6-MAM and cocaine, but less reliable in detecting MMJ.
  • Breath:  This type of test is mainly performed to determine the amount of alcohol in the blood.  Hand-held machine is used to test for alcohol consumption.  Disposable devices are also available over-the-counter.
  • Residue:  Residue tests are generally found in home testing kits.  Parents can use this kit to test their children.  The kit has a pad that picks up drug residue by swiping the pad on the child’s belongings, which is mailed to the manufacturer for testing.  The drawback is that it cannot ascertain if any drug residue found was left by the child under suspicion or by someone else.

What can cause a false positive drug test?

Getting a false positive drug test is a real possibility, though not all tests are 100% accurate.  One can test positive even without active usage of drug.  Ingesting natural substances may also contribute to false positive drug test.  These include food with yeast and poppy seeds, ibuprofen, cold medications and antiretroviral drugs.

Though uncommon, some cases may also report the presence of illicit drugs even though no drugs were ingested.  Lab errors may occur in some cases, but most false-positive drug tests can be attributed to nonprescription drugs or foods that may impact the test.

Some of the substances which could lead to false positives:

  • Secondhand MMJ Smoke
  • Pain Killers
  • Cold Remedies
  • Hay fever remedies
  • Nasal decongestants
  • Diet Pills, Weight Loss Pills
  • Sleep Aids
  • Foods like Poppy Seeds, Hemp Products
  • Antiretroviral Drugs
  • Baby Soaps and Solvents

If found positive for drug use erroneously, one could assess if they had taken any substance that could cause false positive test.

Foods that cause a false positive drug test

A lot of everyday products have led to false positive drug results even without prior exposure to certain drugs.  False positive results are a probability in any drug testing.

Some of the commonly used food items known to cause false positives are:

1. Poppy Seeds

These are small black seeds that contain morphine and codeine naturally.  Ingesting bagels and pastries with poppy seeds may result in test positive results for opioids for up to a whole day after eating.  This most likely happens with labs that still follow the older, lower thresholds for detecting these substances.  It is advisable to wait up to three days after consuming poppy seed products before taking a drug test.

Many opiates are poppy seed derivatives including morphine and codeine.

2. Hemp Seeds

Consumption of hemp food or oil is also believed to cause a false-positive drug test for MMJ.  Hemp seeds or oil can often be found in cold-pressed oil for cooking, salad dressings and nutritional supplements in the form of capsules.  Hemp seeds are an essential ingredient in granola bars that can result in positive tests for cannabis or THC (an active ingredient).

3.Coca Tea

Coca tea is a commonly used remedy in Peru and South America.  It is made with the leaves of the same plant that cocaine comes from.  If anyone uses coco tea regularly, then they may need to stop it a couple of days before their drug test.  Coca tea could affect the screening for up to 36 hours after ingestion.

4. Yeast

One could test positive for alcohol after consuming huge amounts of food containing yeast.  During fermentation of yeast, ethanol is produced as a by-product and could end up being detected via breathalyzer.  Hence, foods such as bread, pizza and pastries should be avoided a few hours before a drug test.

5. Ripe Fruit and Fruit Drinks

Ripe fruits and fruit drinks could also lead to positive tests for alcohol.  When ripe fruits are fermented, it produces enough amounts of alcohol that can be detected by breathalyzer.

One can rinse their mouth with water after ingestion and should be fine after about 15 minutes.

6. Tonic Water

Tonic water contains quinine, an organic compound that is derived from the bark of the South American cinchona tree.  Quinine has a similar composition of opiates.  When consumed in large amounts, it can lead to false positive results for opiates.

Quinine is also used to cut illegal drugs like 6-MAM.

How to dispute a false positive drug test?

Panel tests, also known as immunoassays, utilize paper strips infused with antibodies that react and change color in the presence of a drug or its metabolites.  Panel tests are quick, efficient and easy to conduct, but are susceptible to false positives, i.e., detection of a substance that isn’t actually found in the specimen.  False positives occur when a substance in the specimen has a similar chemical structure to the target substance.  These mimicking substances can be byproducts of prescription or over-the-counter drugs, certain foods or nutritional supplements.

The sensitivity of the test panels is frequently refined in order to reduce the likelihood of false positives.  With the vast and growing number of substances and prescription drugs, there can be masquerade of illicit drugs or their byproducts and false positives will be always an issue with immunoassay testing.

Drugs that are prescribed or over-the-counter have the potential to cause unexpected results in a urine drug test including cold remedies, painkillers, nasal decongestants, cough suppressants, sleep aids, antidepressants, etc.

Foods and Medications that can cause false-positive results:

Cold remedies, hay fever remedies, nasal decongestants


Ibuprofen (Motrin/Advil)

Benzodiazepines, Barbiturates

Coca tea


Sertraline (Zoloft)

Benzodiazepines, LSD

Diet pills


Sleep aids


Beta-blockers (blood-pressure remedies)


Aleve (naproxen sodium)


Quetiapine (Seroquel)


Poppy seeds 


Antihistamines, cough suppressant (dextromethorphan)

Phencyclidine (PCP)

Metformin (Glucophage)

Amphetamine or methamphetamine

Methylphenidate (Ritalin)

Amphetamine, methamphetamine, and LSD

Pseudoephedrine (Sudafed)

Amphetamine and methamphetamine

Diphenhydramine (Benadryl)

Methadone and PCP

Fluoxetine (Prozac)

Amphetamine, methamphetamine, and LSD

Tonic water


Hemp food products


Ibuprofen (Motrin/Advil)


Negative consequences of false positives include:

  • Loss of employment
  • Expulsion from competitive sports
  • Loss of privileges during probation
  • Inappropriate medical care
  • Imprisonment

Factors that could lead to a false positive result:

  • Inappropriate laboratory procedures – Quality controlled procedures should be followed strictly by laboratories while handling samples and performing chemical analysis.  If not handled properly, it may possibly result in erroneous results.
  • Sample mix-up – Mixing up of samples can occur at the collection site if the collectors are negligent in proper sealing and labeling of the samples immediately upon receipt.
  • Accidental exposure or passive inhalation – People may get exposed to substances inadvertently just by eating bagels or pastries topped with poppy seeds, sitting next to someone who is smoking MMJ or being around people who use them.  They could end up testing positive for THC or morphine.
  • Very low cut-off levels – There are some drug testing laboratories that still follow old reference range values.  Hence, anyone with accidental or secondhand exposure to drugs can have a false positive result.  For instance, a person who has consumed pastries, muffins or bagels with poppy seeds or exposed to second-hand MMJ smoke can manifest as a false positive drug test for THC or morphine if the drug test was undertaken at a lab that follows very low cut-off levels.
  • Cross-reactants – Some substances have chemical structures that mirror a targeted drug or its metabolites.  It can be misidentified and result in a false positive result.

If a person’s drug test result returns positive and declines having used any drugs, a confirmatory test such as Gas Chromatography/Mass Spectrometry (GC/MS) can be performed to confirm the claim.

False positives for alcohol can be confirmed by performing blood screening.  Most often, foods and substances that could result in positive alcohol tests do not reach the bloodstream in the form of alcohol.  Therefore, confirmation can be done by performing blood tests.

Advanced testing methods like Gas Chromatography/Mass Spectrometry test (GC/MS test) and the High-Performance Liquid Chromatography test (HPLC test) are used to confirm unexpected false positive drug test results.  These tests are done to separate substances in a selective manner which makes it possible to distinguish drug substances and other ingested materials without the possibility of interference.  Every element separated is marked for identification.

Medications that can cause false positive drug test

There are times when one has to undergo drug test.  There are a number of harmless substances used every day that can trigger a false-positive result for drugs.

1. Antidepressants

    Antidepressants are prescribed for diagnoses like anxiety, depression, panic attacks, obsessive-compulsive disorder, etc.  Several antidepressants tend to cause false positives because of
    cross-reactions.  Some antidepressants like Prozac (fluoxetine), Wellbutrin (bupropion), and Desyrel (trazodone) potentially show up as amphetamines in a drug screen.  Zoloft (sertraline) may show up as a benzodiazepine and also trigger false positives for LSD.

    2. Antibiotics

    Antibiotics usually don’t interfere with drug screens, but there are a few cases where antibiotics are known to trigger inaccurate test results.  Rifampin (used to treat tuberculosis) and fluoroquinolones may show up as opiates in some rapid urine screens.

    3. Antihistamines

    Over-the-counter allergy and sleep medications like Benadryl and Advil PM have diphenhydramine that helps in relieving coughs and runny nose.  These can sometimes surface as methadone, which helps people to quit 6-MAM or other opiates, and can be addictive.  Diphenhydramine may also surface as PCP (an illegal hallucinogenic).  PCP is one of the drugs screened for applicants hired in all federal and private-sector jobs.

    4. Cold Remedies/Decongestants

    Some over-the-counter cold medications contain substances that could lead to a false-positive result for amphetamines.  Brompheniramine, an antihistamine in some cold and allergy medications, have similar elements of methamphetamines when metabolized.

    Vicks inhaler, a nasal decongestant, contains a chemical substance known as levomethamphetamine, which mimics the chemical structure of methamphetamine.

    5. CBD Oil

      Cannabidiol (CBD) is derived from the hemp plant, a relative of the Cannabis sativa plant that produces MMJ.  Some states have permitted CBD oil, edibles and other products to have up to 5% of the mind-altering chemical THC.  Depending on the frequency of use, it is possible to detect MMJ in one’s body.

      6. Antiretroviral or HIV Medication

      Antiretroviral drugs are used to treat retroviral infections, primarily HIV, and prevent HIV/AIDS.  Some antiretroviral drugs contain efavirenz, which usually results in positive tests for benzodiazepine and MMJ.

      7. Antipsychotic Drugs

      Antipsychotic drugs are used for treating mental disorders such as schizophrenia, bipolar disorders, etc.  Quetiapine can show up as methadone and chlorpromazine can come up positive for amphetamine.

      8. Weight Loss Pills

      Phentermine is a prescription medicine that helps curb appetite.  Its chemical substances are similar to amphetamines, a stimulant used to treat ADHD.  Phentermine could lead to false positive drug test if one does not have a medical reason for taking amphetamines.

      9. Anabolic Steroid Abuse

        Dehydroepiandrosterone (DHEA) is an endogenous androgenic steroid produced by the adrenal glands, gonads, and brain.  It is made naturally by the human body.  DHEA is also available as nutritional supplement, made synthetically using soy and wild yam chemicals.  These are used by bodybuilders and athletes to increase muscle, enhance athletic performance, decrease fat and body appearance.

        Steroid-screening results are considered positive when the ratio of testosterone to epitestosterone (T/E) exceeds 6:1.

        10. Proton Pump Inhibitors

        Proton pump inhibitors are medications such as Nexium (esomeprazole), Prilosec (omeprazole), and Prevacid (lansoprazole) used to treat gastroesophageal reflux disease (GERD) or peptic ulcer disease.  These drugs can cause a false positive for THC.

        11. Mouthwash

        Many breath-cleaning products, liquid medications and vanilla extracts often have ethanol, a form of simple grain alcohol.  Drug tests can detect even traces of alcohol.  So if anyone uses products containing ethyl alcohol, their breath, blood or urine sample might show possible signs of drinking.  The same could happen with alcohol-based hand sanitizers if used regularly.

        12. Passive Weed Smoking

        Constantly being around people who smoke MMJ could result in a positive result.  Research shows that non-smokers in a confined space with people smoking high-THC MMJ described mild subjective effects of the drug and exhibited mild impairments on performance in motor tasks.  Hence, there is a high probability of positive result when being around or exposed to frequent MMJ smokers.

        13. Baby Soaps and Solvents

        Newborn babies with congenital anomalies are usually tested to see whether the mother used drugs during pregnancy.  Branded solvents usually tested positive for cannabis, even without prior use of MMJ by the mother.

        Although it is still unknown why the soaps lead to positive test results, it is possible that some of the soap ingredients contain the same chemical structure as THC, the active ingredient in cannabis.  There are still some speculations, but it is still unknown how the soap residues on the skin make their way to the urine.

        Herbs that can cause false positive drug test

        Furthermore, consumption of foods containing hemp products such as hemp-seed oil has resulted in positive drug test for MMJ.

        Ephedra is an herbal plant known as plant Ephedra sinica.  The branches and tops are used for medicinal formulation; even the whole plant or root can be used.  Ephedra contains the chemical substance ephedrine which stimulates the heart, lungs and nervous system.

        Ephedra is used to enhance athletic performance, to aid in weight loss and obesity.  The medicinal formulations are used to treat allergies, nasal congestion and respiratory tract disorders like bronchospasm, asthma, bronchitis, etc.  Ephedra is also used as a “water pill” to increase urine flow in people with fluid retention.

        Ephedra is also sold as a recreational drug (herbal ecstasy).  Ephedra and other products that contain active ingredients in Ephedra or combination products containing Ephedra, other natural stimulants such as guarana and cola nut, and Ephedra-containing dietary supplements are banned in the United States due to the potentially serious side effects.

        Ephedra containing products may lead to false positive methamphetamine result.

        Poppy seeds do contain small amounts of opium and consuming poppy seeds may seldom yield a positive drug test result.  While processing the poppy seeds, most of the opium content gets removed.  Traces of codeine and morphine may be found in the urine up to two days after consumption of poppy seeds from baked items like pastries, muffins, cakes and bagels.

        According to the USADA (United States Anti-Doping Agency), WADA-licensed laboratories can report a urine sample as positive for morphine when the level exceeds 1.3 mcg/mL.

        Other most herbal products or supplements, teas beverages are less likely to cause false-positive test results.  A study done on saw palmetto, ginseng, gingko biloba, garlic, green tea, valerian, cranberry, St. John’s wort, herbal teas and drinks, etc., did not cause any false-positive reactions.  Assessing the usage of these products cautiously can help minimize misinterpretation of drug screening results.

        On the initial screening called immunoassay, if an individual gets a false positive result, then he or she can request a more in-depth urinary drug test called gas chromatography or mass spectrometry screening.  GC/MS screening tests are more specific, have less cross-reactivity to herbs, teas and beverages, and minimize the possibility of a false positive, but is more expensive.

        Can B12, sudafed, albuterol cause false positive drug test?

        Even in the case of not using recreational or prescribed drugs, there could be a probable chance of false positive on a drug test.  Before taking a drug test, one could research on medications and foods that could lead to false positive results.

        1. Vitamin B Supplements

          Consuming plant-based products that contain vitamin B12 or riboflavin may result in cannabis false positives.  Riboflavin is commercially produced from hemp seed oil or fermented lactose carbohydrates, which contains traces of tetrahydrocannabinol (THC).  THC is a psychoactive ingredient of MMJ, and can result in false positive.

          2. Albuterol

          Albuterol is a bronchodilator used to prevent and treat breathing problems due to asthma, chronic obstructive pulmonary disease and other lung diseases.  It is also used for exercise-induced shortness of breath.

          There are studies showing metered‐dose inhalers (MDI) contain ethanol that could lead to a false‐positive breathalyzer test.  Small amounts of ethanol can be found in some brands of salbutamol MDI.

          MDIs may elevate the breath alcohol readings above the legal limit for intoxication.  The effects are transient and can be prevented by a time interval of 10 minutes between the use of a metered‐dose inhaler and breath alcohol testing.

          3. Sudafed

            Sudafed, which is also known as Pseudoephedrine, is used in the treatment of allergies, sinusitis, breathing problems and nasal congestion.  Sudafed can cause false positive for amphetamines or methamphetamines.  Therefore, it is advisable to avoid using Sudafed for at least 48 hours before a drug test.

            Preventing False Positives

            • If concerned antidepressant might show up as a false positive, the best course of action would be to be proactive.  It is better to declare about any drug usage before the test rather than after.  One can inform the technician about the antidepressant use and show the prescription as a proof, and ensure it is mentioned on their record.
            • Due to the high chances of false positives, all drug screen results should be confirmed through gas chromatography or mass spectrometry technique.
            • One can demand for a second confirmation test if initial drug screen returns false positive, preferably with the same sample.  One should also confirm that a different technique was used by obtaining the copies of both results.

            Preparation for the Test

            Most importantly, one should not stop taking the medications or reduce the dose without the advice of a physician.  One can declare about any drug usage before the test and divulge prescriptions as proof.

            Short-term interruptions can have serious consequences for the treatment of any condition and lead to antidepressant discontinuation syndrome (ADS).  One can discuss their concerns with their health provider or psychologist in order to take the drug screen safely and without stress.

            A Word of Advice

            Anyone can feel anxious to face a drug screen, especially in jobs where it is mandated.  It is better not to emphasize unduly about taking a drug screen and one should remember false positives do occur and that most drug screening companies do understand this.  Simply divulge the prescriptions so that false positives can be avoided and rights can be preserved.

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