Drug tests are performed for various reasons such as employment, competitive sports, schools, colleges, healthcare followup testing, etc. Drug testing is generally done to look for the presence of illicit drugs or substances. Generally, the results are either positive or negative for drugs; however, there are instances where the drug test could result in false positive.
A false-positive result signifies the test has found the presence of substance in the specimen provided even though the person hasn’t ingested any drugs. Though uncommon, false-positive results can occur in some cases.
On certain occasions, false-positive results can occur due to every day substances that we ingest such as foods, mouthwash, cold and cough medications, painkillers, CBD oil or other substances and even due to passive consumption such as weed smoke.
False-positive results can also occur because of cross-reactivity during immunoassay test and these are confirmed by highly accurate screening method such as Gas Chromatography/Mass Spectrometry (GC/MS).
If you have tested false positive for any substance despite not taking any drug(s), you can definitely demand for a retest. Let’s find out if the substances that we use every day can cause false positive results…..
Table of Contents
- Everyday Substances That Can Cause A False Positive Drug Test
- Substances That Can Cause False Positive Drug Test
- Food Products
- Passive Weed Smoking
- Mouthwash
- Baby Soaps
- Tonic Water
- Coca Tea
- CBD Oil
- Corticosteroids
- Nonsteroidal Anti-Inflammatory and Analgesic Drugs
- Antiretroviral Drugs
- Antidepressants
- Sympathomimetic Vasoconstrictor Drugs
- Weight Loss Pills
- Cold Medications
- Antibiotics
- Antihistamines
- Antipsychotic Drugs
- Drugs That Cause False Positives
- Consequences of a False Positive Drug Test
- Confirmatory Tests
- Bottom Line
Substances That Can Cause False Positive Drug Test
Substances that we use every day can sometimes cause false-positive results. Sometimes, these false positive results can lead to some unwanted repercussions. For instance, if you are being drug tested during employment or pre-employment, you may be suspended, fired or your job offer may be revoked in the case of false-positive result.
Every day substances that can cause false positives include
- Food Products
It may sound weird that food can be one of the sources of false-positive results on the drug test. Some of the ingredients (mentioned below) when added to the edibles can trigger a false positive result for illicit substances.
- Yeast: Foods such as bread, pizza and ripe fruits should be avoided before taking the drug test since it can lead to false-positive result for alcohol. These food products contain yeast and when consumed in large amounts can result in alcohol positivity if subjected to breathalyzer test. When the yeast gets metabolized, the by-product formed is ethanol. During metabolism, this ethanol can lead to false positive for alcohol.
- Hemp Seeds: Hemp seeds are used in granola bars and cold-pressed oil is used in cooking, salads and nutritional supplements. When hemp-containing foods are consumed in large amounts, the drug test may show false-positive results for THC.
- Poppy Seeds: Poppy seeds are edibles used every day for different purposes. The seeds contain narcotic substances naturally. Pastries, bagels and muffins sprinkled with poppy seeds might result in a false positive for OPI during drug test for up to a whole day after consumption. This might happen in cases where the lab follows old threshold values for the detection of OPI.
Poppy seeds are used to make cake and porridge. It is also used to treat diarrhea, constipation, cough, asthma, sleeping problems, etc., just by chewing the seeds by mouth.
Due to the false-positive results yielded by poppy seeds, the Department of Health and Human Services raised the cut-off threshold for OPI to 2000 ng/mL. This increase was required to differentiate from the people who abused drugs to those who used them for medical purposes.
- Passive Weed Smoking
Weed is consumed in different forms by most people in their daily life. Some use it on a regular basis, while some infrequently. However, a person frequently exposed to second-hand weed smoke may also test positive for THC on a drug test.
There are probabilities of false-positive results for THC if the person screened for the test is restricted in the same room as the smokers because of inhalation of smoke exhaled by the smokers. Even if a person hangs out often with someone who smokes weed, traces of THC could be found in the urine due to smoke exposure. If a person has enough THC in the body during drug screening, this could trigger a positive result. Further tests will be required to confirm the traces of THC.
Thus, the researchers concluded that exposure to cannabis smoke can produce a positive urine test at common cut-off concentrations. They also noted that these positive results are likely to be rare because testing should occur within a few hours of exposure.
However, due to the modernization in testing, false-positive results to second-hand smoke are mostly unlikely.
- Mouthwash
Many liquid medicines and breath-cleaning products have ethyl alcohol in them. Drug tests can detect traces of alcohol and even for a longer period after last consumption. Hence, if you consume any product containing ethyl alcohol, your breath, urine or blood specimen might show up signs of alcohol consumption.
Alcohol-based hand sanitizers when used regularly can result in false-positive result.
- Baby Soaps
Mothers bathe and wash their infant babies often using the solvents such as body lotion, soothing relief creamy washes, bathing soaps, etc. When babies are tested due to congenital anomalies, their samples result in false positives for THC even though the baby and the mother were never exposed to cannabis products. Regular use of solvents has resulted in false positives for THC.
Babies can be born with congenital anomalies if the mother consumed cannabis products during pregnancy. Hence, babies with anomalies are tested for THC in their system.
It is an unknown fact how the traces of THC get into the babies’ system. Some healthcare professionals contemplated that the chemical structures of some of the elements in the solvents mimicked THC metabolites. It still remains a mystery as to how the soap contents get into the babies’ system.
- Tonic Water
Tonic water is a carbonated soft drink that consists of quinine (used to treat malaria) and considered safe if taken in small amounts. Some people mix tonic water with illicit drugs and this can surface as OPI during drug tests. There are reports stating that a positive result showed on a urine test for the traces of antimalarials due to the consumption of tonic water in a mixed drink.
- Coca Tea
Coca tea is a popular traditional home-based medication in Peru and South America. This tea is made with the leaves of the plant that COC is manufactured. This substance will linger in a person’s body for up to 36 hours after consumption. Drinking this beverage could lead to false-positive results for the presence of COC. Thus, researchers have concluded that healthcare professionals should consider the history of coca tea consumption before taking the drug test.
If any individual has an upcoming drug test, stopping coca tea for a few days would be advisable.
- CBD Oil
Cannabidiol (CBD) is a non-intoxicating compound found in the cannabis plant. CBD products are naturally derived from hemp, which is a legal low-THC type of cannabis. It has anti-inflammatory, pain-relieving and anti-anxiety properties, and used as a sleeping aid. CBD is available in the market in various forms such as CBD oil, edibles, tinctures, vape oil, sublingual drops, pills, capsules, creams, lotions, etc.
Drug tests detect for the presence of THC, which is an active ingredient of weed. If enough amount of THC is present in the system, it will be detected on the drug test. In general, CBD itself is not detected on a drug test, but consuming CBD products regularly can lead to positive results due to accumulation of THC present in these products.
People purchasing CBD products should ensure that it contains less than or equal to 0.3% THC.
- Corticosteroids
These medications belong to the class of substances called glucocorticoids. These have anti-inflammatory properties and used as immunosuppressant in organ transplants, grafting, etc. These drugs are also used in the treatment of asthma, rheumatoid arthritis, colitis, allergic conditions, etc. Some brands of corticosteroids can surface as false positive for steroids.
Some drugs are used to cure high calcium levels caused by adrenal gland or cancer and also to suppress the immune system.
People using corticosteroids can have false-positive result for steroid. In such cases, one can inform or provide their prescription and medical records if necessary before taking the drug test.
- Nonsteroidal Anti-Inflammatory and Analgesic Drugs
These drugs are commonly prescribed by doctors to cure inflammation, sickness, fever, arthritic pain, etc. Consuming high doses of these drugs can cause false-positive results for THC, BAR and PCP within three hours. The preliminary drug test such as immunoassay can detect traces of THC and the result can be further confirmed by GC-MS or high-performance liquid chromatography method to determine if the result is positive or false positive.
Studies have shown that people taking high doses of nonsteroidal anti-inflammatory and analgesic drugs have tested false positive for THC and people consuming sleeping pills along with some of these medications also tested positive for BAR. Thus, the results concluded that even a small amount of anti-inflammatory drugs can result in false positive.
- Antiretroviral Drugs
Antiretroviral drugs are used in the treatment of human immunodeficiency virus (HIV) infection. The efavirenz component during drug test shows up as THC and BZO in the blood. This can mislead the donor to be abusing illicit drugs. In such cases, confirmatory tests are required to determine if the person is abusing drugs or not.
People being treated for HIV infection with antiretroviral drugs may be tested positive for THC and BZO. Anyone taking drug test in other circumstances should inform about their medical condition as well as the medications they are taking so that it can be interpreted in the right way.
- Antidepressants
Antidepressant medications result in false-positive results. This is prescribed for depression, mental disorder, panic attacks and many more. A majority of the antidepressants have similar chemical structures to AMP and BZO.
During metabolism, the antidepressant medication is broken down in the body and forms metabolites that have similar chemical structures to BZO. This can cause false positives for BZO or AMP during drug screening.
You will be required to undergo drug test while seeking employment in an organization. If you are taking any antidepressants for any condition, it is advisable to inform the employer about the usage before taking up the drug test rather than later.
- Sympathomimetic Vasoconstrictor Drugs
These medications are used to treat sinusitis, breathing difficulties, nasal allergies and congestion. Some of the vasoconstrictor drugs can lead to false-positive results during drug testing. Drug manufacturers use AMP in some of the sympathomimetic drugs. During metabolism, traces of Mamp or AMP can be found in the blood and will linger in the body for up to 2 days after last ingestion.
- Weight Loss Pills
Appetite suppressants are generally prescribed in weight loss programs. These drugs have similar chemical structures to AMP, which stimulates metabolism and suppresses appetite. AMP is a stimulant used in the treatment of attention deficit hyperactivity disorder (ADHD) and taking weight loss pills can contribute towards false positives for AMP in the urine specimen.
Consuming weight loss pills can result in false-positive result for AMP.
- Cold Medications
Cold medications contain antihistamine compounds that could result in false-positive results for AMP. The medications bought from a drug store or over-the-counter may contain antihistamines, which when metabolized in the body results in similar by-products to Mamp. Inhalers used for nasal congestion also contain L-enantiomer of Mamp, which has a similar structure to Mamp. Donors may test false positive for Mamp even if not consumed Mamp drugs.
However, there are reviews stating that the latest drug tests can differentiate between Mamp and the chemicals in the inhaler. Hence, the chances of cold medications leading to false positives are slim.
- Antibiotics
In general, antibiotics do not intervene with drug test results, but some medications can produce inaccurate test results seldomly. Antibiotics used in the treatment of tuberculosis might show up traces of OPI on rapid urine drug test.
Antibiotics are commonly used to treat urinary tract infections, sinusitis, pneumonia, etc. Some of these medications cause false positive for OPI. These medications also cause false positive for AMP and MAMP.
A single-dose antibiotic may stay in the human body for more than 18 hours after the last use. Generally, some antibiotics may interfere with the drug test and show up as OPI.
- Antihistamines
Antihistamines are used to treat allergies, hypersensitive reactions, cold, cough and runny nose. Some of the brands used may show traces of MTD during drug screening. Some other brands may intervene and show up as PCP, which is an illicit hallucinogenic drug. PCP is one of the five types of drugs that is screened during employment in many private-sector jobs.
- Antipsychotic Drugs
In general, many of the antipsychotic medications taken for mental disorders can lead to false-positive test results. These drugs are commonly used to treat bipolar disorder and schizophrenia, and often surface as MTD on a urine drug test. A few other brands of this class of drugs can also result in false positives for stimulants, AMP.
Drugs That Cause False Positives
Some of the prescription and over-the-counter medications can interfere and produce false-positive results for illicit substances. If any of the following medications resulted in a false-positive drug test, try to stop or reduce the dose by consulting with your healthcare professional. Then, you can take a retest or a confirmatory test to check the results.
- Cough Suppressants: Some of the brands and over-the-counter cough suppressants can cause false positives for OPI and PCP on the drug test. During metabolism, traces of OPI or PCP may be found in the urine specimen.
- Opioid Analgesics: These medications are used to treat moderate to severe pain. Some types of these drugs could show false positive for OPI or PCP.
- Beta-Blockers: Alpha and beta-blocker drugs are prescribed by physicians to control blood pressure. Drugs that are designed to block both alpha and beta-adrenergic receptors have a tendency to trigger false positive for AMP, MAMP or LSD.
- Calcium Channel Blockers: The calcium channel blockers are also prescribed to treat hypertension and atrial fibrillation. Using this medication can result in a false positive for LSD.
- Stimulants: Stimulants are used to treat ADHD. A few stimulants can show up as false positive for AMP, MAMP and LSD.
- Sedatives: Over-the counter sedatives can result in false positive for MTD or PCP.
- Proton Pump Inhibitors: Proton pump inhibitors are used to treat gastroesophageal reflux disease and heartburn. Consuming these medications regularly could result in a false positive for THC.
- NSAIDs: Some of the over-the-counter nonsteroidal anti-inflammatory medications can surface up as a false positive for THC, BAR or PCP.
Consequences of a False Positive Drug Test
Drug test results can negatively affect many situations and therefore accuracy is very important. A positive drug test result indicates the presence of illicit substance(s) in the body. Rapid drug testing such as immunoassay may sometimes give false positive results due to cross reactivity even if the donor didn’t use or abuse any drugs.
False positives can occur due to:
- Faulty Testing Methods: Incorrect results may occur if the drug testing process is mishandled.
- Low Cut-Off Level: If the drug testing lab uses a minimum threshold value to detect drugs, there can be a possibility for positive result. For instance, second-hand smoke from weed can trigger a positive result at low cut-off level.
- Cross-Reactivity of Substances: Some other substances which are similar to illicit drug metabolites may also be detected during drug screening. For instance, poppy seeds are falsely shown as the presence of OPI in the body.
The drug test result depends on the type of screening test, processing of the test and the amount of substance an individual has consumed. Due to the advancement in drug testing technology, false-positive results are becoming less common. The negative effects of false-positive drug test include:
- Loss of job
- Unfitting medical care
- Prison punishment or jail term
- Rejection from competitive sports
- Privation of privileges during probation
Confirmatory Tests
Initial false positive results are generally confirmed through Gas Chromatography, Mass Spectrometry method. In some cases, confirmatory test may result in a false positive. If the donor’s drug test result returns positive on the confirmatory test, the donor may visit rehabilitation center to get back to sobriety and become drug free.
It is prudent to inform if you are taking any medications before taking up the drug test. If you have failed to inform before the drug test and do not use any illicit substances, you can register your protest and take up second confirmatory drug test.
Confirmatory tests such as Gas Chromatography-Mass Spectrometry and High-performance Liquid Chromatography can provide reliable and accurate results. These tests are more expensive and require advanced equipments to distinguish within the same class of drugs.
Bottom Line
During drug testing, there is always a possibility for false positive result, which can be triggered by every day substances such as food, cold medications, soaps and solvents, passive smoking, etc.
If your preliminary tests return back as false positive, you should request for confirmatory testing if you are confident about not taking any illicit drugs before the drug test. If the second confirmatory test also returns positive, you can seek help through rehabilitation center to become sober and drug free.
It would be wise to inform the employer or the person in-charge if you are taking any prescription or over-the-counter medications before taking up the drug test.
