What Can Cause False Positives for Drug Test?

As the phenomenon of drug testing is common for the recruiting job-false positive drug test term is also frequent to hear. Based on various usual reasons, the drug test may affect your success in getting the job. It is an embarrassment and shock for the person who abstains from drugs but gets the tests positive for drugs. If you are preparing to pass a drug test and want to avoid the embarrassing situation, it is indispensable for you to know what is a false positive drug test and how it can occur. So, keep on reading to avoid the chances of positive results.

What Does a false Positive Test Mean?

Basically, a drug test results positive for the presence of certain illicit drugs like marijuana, opiates, or heroin. The term false positive results refer to the detection and screening of drugs in the body that a person has not taken actually or intentionally. Medication, drugs, food, and various other substances can cause false-positive results for the drug test. Common cough, sleep, and pain relief medicines can trigger positive results for the drug testing.

Drug test screen for the presence of the following drugs in the sweat, blood, urine, and mouth swab samples.

  • Marijuana (THC)
  • Cocaine
  • Amphetamine
  • Barbiturates
  • MDMA
  • Steroids
  • Phencyclidine (PCP)

What Medications Can Cause a False Positive?

Next info given by FMA Health. Here is the complete list of the medications that can hinder the results of your drug tests by staying in your metabolism. If you already know about your drug test, either it is for marijuana or opiates, you should avoid intaking these medications. Although the improvement in the drug testing procedure has lessened the chances of mistakes, yet there are false-positive results. Keep in mind that biological samples matter. Passing hair follicle drug test is the most challenging things, because a hair preserves a lot of metabolites.


NSAIDs refer to the non-steroidal anti-inflammatory drugs that are basically used to relieve pain and inflammation. Among the NSAIDs, two major classes of drugs are used, including ibuprofen (Motrin, Advil) and naproxen (Aleve).

Intaking any of these medicines can lead to the detection of THC, PCP, or barbiturates in your sample for the urine drug test.

But here another question arises that how long does the ibuprofen stay in your system that can cause you to fail a drug test? Well, the answer is in your favor, ibuprofen is metabolized in the body within 24 hours and is eliminated through urine and after 24 hours you will get no traces or metabolites of drugs by the ibuprofen.


Various classes of antidepressant medications have known to cause false-positive results. Besides our described medications, there are several other drugs with the potential for false-positive screening. Before intaking any antidepressant medication, consult your doctor if these can interfere with the results.


It is used to treat depression and anxiety and may result in the screening of amphetamine, methamphetamine, and LSD.


Also known as Seroquel is used to treat bipolar diseases, insomnia, and depression may result in the detection of opiates or methadone.


Venlafaxine antidepressant is used to treat depression, anxiety, and panic attacks-may result in the detection of false-positive for PCP urine drug test.


Various tricyclic antidepressants (TCA) treat chronic nerve pain, depression, and relieve migraines. Amitriptyline is a TCA that can test false positive for the hallucinogenic drug, LSD. Other TCA which can cause false-positive tests are listed as:

  1. Imipramine (Tofranil)
  2. Desipramine (Norpramin)
  3. Doxepin (Zonalon, Prudoxin)


Ciprofloxacin, Ofloxacin, and Levoflaxin are commonly known as Quinolone Antibiotics. These antibiotics are used to treat urinary tract infections, sinus infections, and respiratory tract infections.

Quinolone antibiotics have the potential to cause false positive drug tests for amphetamine, methamphetamine, and opiates.


Antihistamines are the drugs used to relieve the symptoms of allergies, such as hay fever, hives, and also treat insomnia. Certain medications like Benadryl or Deoxylamine contain Diphenhydramine that result in false positive for THC, PCP, barbiturates, methadone, or opiates.

Central Nervous System Stimulants

ADHD is a neurodevelopmental disorder affecting the mental condition to pay attention and to act. Medications such as Ritalin and Adderall treat the ADHA have the potential to test false positive for amphetamine and methamphetamine.

Cough Suppressants

Over-the-counter cough suppressants like Robitussin and Delsym contain the active ingredient dextromethorphan that can cause a false-positive test for PCP or opiates.

Decongestants and Sleep Aides

A decongestant is a medication that relieves nasal congestion in the upper respiratory tract infection. Sudafed or pseudoephedrine for nasal or sinus congestion can result in a false positive for amphetamine and methamphetamine.

The key ingredient of over-the-counter sleeping aid Unisom is doxylamine can cause false positive drug tests for PCP or methadone.

Proton Pump Inhibitors

Proton pump inhibitors are used to treat GERD, Peptic ulcer, and H. Pylori by reducing the amount of stomach acid. Various proton pump inhibitors like Prilosec (omeprazole), Prevacid (lansoprazole), Pantoprazole and Nexium (esomeprazole) can result in a false-positive test for THC or USD drugs. If we count for the major medications that can cause the false positive drug test for THC, then proton pump inhibitors are the notable culprits.

HIV Medication

Efavirenz or Sustiva is an anti-HIV medication that can result in a false-positive test for THC or benzodiazepines.

Some Common Substances that Can Cause False Positive

Besides the medications, there are some common substances that can cause false-positive results. These substances include:

Vitamin B Supplements

Vitamin B2 also known as Riboflavin is derived from hemp seed oil. Intake of these plant-based products may cause the false positive test for the THC.

Tonic Water

Consumption of a high quantity of tonic water induces the quinine (treat malaria) in the body which results in the false positive for the screening of opiates.

Secondhand Marijuana Smoke

Exposure to a high concentration of secondhand marijuana smoke even at a concert can cause you to fail a drug test. THC may be detected in the urine but modern tests are at less risk of false-positive results from secondhand marijuana smoke.

Poppy Seeds

Poppy seeds contain a trace amount of opium that may interfere with the results of drug tests. It is commonly used in porridge and cake making and also to treat constipation and diarrhea. Here you may want to know how poppy seeds can make you fail a drug test. Consumption of poppy seed foods like the bagel or muffin before the drug test can cause you to fail with the consequences of false-positive results for morphine and opioids. Even the bite of a poppy seed cookie can take two days for its complete breakdown.


Some medications such as mouthwash, breath cleaning products, hand sanitizer, or other liquid medications can test false positive for the alcohol screening. Even the trace amount of alcohol can be detected for drinking in the breath, blood, or alcohol sample.

Weight Loss Pills

Phentermine is a prescription drug that is used to treat obesity and is similar to amphetamine. These weight loss medications can cause false-positive tests for amphetamine screening.


CBD oil has its potential role in relieving pain, anxiety, and depression. The CBD comes from the hemp plant with various useful benefits-also used in edible oils. As the CBD is present in various things from drinks to oils and from powders to weight loss pills, so the drug tests for THC may result in false positives for the CBD oil. Specifically, the drug test can detect the THC in the urine samples.

Pain or Anti-inflammatory Medications

Several pain killers are used normally by the patients that may result in false-positive tests. Intaking non-steroidal anti-inflammatory drugs like Tramadol or Ultram can result in the detection of opiates or PCP.

Antipsychotic Drugs

Some medications taken for mental disorders can be detected as drug metabolites in the sample leading to false-positive results. The medicine for treating bipolar disease and Schizophrenia-Quetiapine-can indicates the presence of methadone in the body. Another antipsychotic medicine chlorpromazine can cause false-positive tests for amphetamine screening.

Baby Soap

Baby soap is common to use by mothers to wash their babies during the day. Mothers can use the solvent such as Aveeno Soothing Relief Creamy Wash and CVS Night-time Baby Bath. Interaction with the baby soap can cause the detection of false marijuana in the samples. Various studies found that the chemicals in the baby soap-polyquaternium-11 and Cocamidopropyl betaine resemble in structure with THC. Owing to the similarity in structure the baby soap can cause a false positive for THC.

Coca Leaf Tea

Coca tea is made from the leaves of the plant from where the cocaine comes. Drinking coca leaf tea can cause false positives for cocaine screening. If you know about your drug test, quit using the tea many days prior to the test. Because the coca leaf tea can affect your cocaine screening for about 36 hours after drinking.

Other Medication That Can Cause False Positive

Some other common medications can also cause false positives for various opiates, amphetamine, methamphetamine, LSD. These are listed as:

MedicationTests False Positive
Sertraline (Zoloft)LSD, Benzodiazepines
Fluoxetine (Prozac)LSD, Amphetamine, Methamphetamine
Metformin (Glucophage)Amphetamine, Methamphetamine
Bupropion (Wellbutrin)LSD, Amphetamine, Methamphetamine
Diltiazem (Cardizem)LSD
Labetalol (Trandate)LSD, Amphetamine, Methamphetamine
Oxaprozin (Daypro)Benzodiazepines

How To Dispute a False Positive Drug Test?

In case, if a person doesn’t take drugs but tested positive then he should review the medications that can possibly cause the positive results. Keep reading FMAHealth to get know more about it.

More specifically, he can look for the detail and procedure of drug testing and screening.

  • If the specimen has not been adulterated.
  • Did the coughing and sneezing of any ill person have contaminated the sample.
  • Was the staff using PPE and the facility was well equipped and clean.

If you want to retake a drug test, then reach out to your pharmacist and get information on what medications and OTC can cause positive results. Negotiate with the pharmacist if he provides the written documentation for the effect of medication on the drug tests and brings the copy to the testing officer. A confirmatory test with the GC/MS and HPLC can reveal the interfering substance and provide more authentic and efficient results.

Stats show that 15% of the drug test remain false positive-so, you are not alone in the line of validating the accuracy of drug tests.


Either it is the random drug test or initial immunoassay test, the concentration of several drugs can be detected. More often, false positive drug tests happen despite the advancement in the procedure and techniques and the accuracy and efficiency of the drug testing and screening process. The effect of medication on drug testing can help you to properly detox the body and take action in case of a false-positive result when you are not actually intaking the drugs. Read about drug testing myths to know more. From medications to food lists, several things are responsible for the detection of drugs in the mouth swab, saliva, urine, or blood drug test. Consult your pharmacist to get a written copy of the effect and then request for the retaking of the drug test.


  • Carolyn Gaughan

    Carolyn Gaughan is an ex-executive vice president of the Kansas Academy of Family Physicians and represents the state associations of the American Academy of Family Physicians and the American College of Osteopathic Family Physicians.