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What Can Cause False Positives For Drug Tests?

You may ask, “what can cause a false positive on a drug test?” To answer this, you must first understand what false positives mean. False positives refer to a test result that inaccurately indicates a certain substance, attribute, or condition is present. You can also refer to a false positive as a mistake in a two-fold classification that wrongly states that a specific thing is current. To put this in a practical scenario, someone can wrongly test for specific substances or drug metabolites in a urine, hair, or saliva drug screening.

It’s the direct opposite of a false negative. Now that you know what a false positive means and how it applies to a drug testing result, the next thing is to know its causes. Some certain medications and substances can cause positive results in drug tests. This begs the question, “what medications can cause a false positive?”

Medications that Cause False Positive Drug Tests


Analgesics / NSAIDs (Ibuprofen, Naproxen)

This medication will cause a false positive if you’re testing for marijuana, barbiturates, or benzodiazepines. This medication is a pain reliever that you can get over the counter. According to DUIIllinois, 12 grams of Ibuprofen can mess with the enzyme used for drug testing. This isn’t just restricted to Ibuprofen. NSAIDs, in general, are known to trigger false positives. If you have to take a pain reliever and don’t want one that will mess with the result of an upcoming drug test, we recommend going for Aspirin.


These types of medications can cause a false positive drug test result if the substance that’s tested for is either LSD or Amphetamines. To prevent losing your employment over an inaccurate result, the best line of action is to inform the lab technician ahead of time. Popular examples of antidepressants that can cause false positives include the following:

  •       Wellbutrin
  •       Amitriptyline
  •       Seroquel
  •       Prozac
  •       Effexor



Antibiotics are anti-microbial elements that fight against disease-causing bacteria or bacterial infections. When administered, they will either inhibit or eliminate the growth of such bacteria in your body. When you have a sinus or urinary tract infection, it’s very likely that you’ll be prescribed antibiotics, particularly Quinolone antibiotics such as Cipro or Levaquin. Antibiotics are known to cause a false positive result if you’re doing a drug screen for opiates.



Antihistamines can be purchased without a prescription, and it’s generally inexpensive. These medications are used to treat the common cold, influenza, and allergic rhinitis. It’s usually used for short-term treatment of the above-mentioned infections. These medications, precisely those ones containing Doxylamine, will cause false positives in your drug test result if you’re testing for methadone, PCP, or Opiates. Popular examples of antihistamines;

  •       Benadryl
  •       Unisom (Doxylamine)

Central nervous system (CNS) stimulants


These drugs are known to heighten certain chemical levels in the brain resulting in increased physical alertness, attention, and energy. If you use CNS stimulants, your heart rate, breathing rate, and blood pressure will be enhanced. The outcome will be a false positive if you’re on these stimulants and undergo a drug test for amphetamines or methamphetamines. Popular examples of these medications include;

  •       Ritalin
  •       Adderall

Cough Suppressants


These medications describe any drug that’s taken to give you relief from a cough. Many cough suppressants have a common ingredient known as Dextromethorphan. This ingredient causes a drug screen for opiates and PCP to come up with false positives. Examples of such cough suppressants include;

  •       Delsym
  •       Robitussin-DM



Decongestants are medications that lessen inflammation, swelling, and the accumulation of mucus around the eyes or nasal pathways. They come in varieties – some are consumed orally, while others are either dropped in the eyes or sprayed on the nose to relieve congestion. Decongestants generally have a common ingredient known as Sudafed, which is also an ingredient used to manufacture methamphetamine. So if you use decongestants and undergo a drug screen for amphetamines and methamphetamines, the outcome will be a false positive. Common examples include:

  •       Zephrex-D
  •       SudaGest

Sleep Aids


Sleep Aids can also be referred to as sleeping pills. These medications help you manage sleeping disorders such as insomnia. Taking these drugs will help you fall asleep. They also help you to sleep longer than your usual time. Just like antihistamines, sleeping aids contain Doxylamine. These medications can trigger false positives for methadone, PCP, and opiates. Diphenhydramine is a well-known example of a sleep aid.

Proton Pump Inhibitors


These medications are used to reduce stomach acid production in your body for an extended period. This acid comes from the H⁺/K⁺ ATPase proton pump, and this drug works by inhibiting it. It’s a medication prescribed for people suffering from peptic ulcers or gastroesophageal reflux. This drug answers the question, “what medications test positive for THC?” Examples of this medication include;

  •       Prevacid
  •       Nexium
  •       Prilosec

Novocaine or Lidocaine


These medicines are anesthetics commonly used by dentists to make their patients numb to the pain of the procedure they’re about to undergo. These medications obstruct pain signals to the brain. Before these drugs existed, cocaine was used for this function.

Novocaine or Lidocaine causes false positives for a drug test screening for cocaine. In this case, a report from your dentist will be needed to show that you’re not using cocaine, or you can inform the lab technician about your appointment with the dentist before the procedure.

HIV Medication


People living with HIV and using medications to manage the health disorder are likely to test positive for benzodiazepines or THC. The good thing is that a confirmatory test can be taken to be sure that it’s the medication (Efavirenz) in the body, not cannabinoids. When it comes to false positives, HIV medications answer the question, “what medications can cause a false positive on drug test?”

Common Substances that Cause False Positives


Aside from medications, certain substances can also cause false positives for a drug test. They include:

Vitamin-B Supplements


These supplements contain a chemical compound known as Riboflavin. This compound is also referred to as B2, an active compound in hemp seed oil extracted from the same plant as CBD oil. If you’re taking Vitamin-B supplements, you’ll likely test positive for THC.

Tonic Water


Tonic water is a processed drink that contains dissolved quinine. Quinine is a chemical compound that treats malaria. When this compound is present in large amounts in the body, you can test positive for an opiate screen. If you’re a regular consumer of tonic water, you may want to reduce your intake to prevent a false-positive test result.

Secondhand Marijuana Smoke


Secondhand marijuana smoke is what weed smokers exhale. If you stick around someone who smokes weed frequently for a prolonged period, you’ll likely have THC on your hair and clothes. You’ll also inhale what the smoker is exhaling. This is how the drug toxins enter your bloodstream and body fluids. It also explains why you may get high when you’re around heavy weed smokers for a while. So, can you fail a drug test from secondhand smoke at a concert? Yes, you can.

Poppy Seeds


You may have heard of or even used poppy seeds. These are oilseeds extracted from the opium poppy. These seeds are good for the body because they contain high levels of iron and improve blood circulation.

You may ask, “will poppy seeds make you fail a drug test?” The short answer is yes. This is because, despite these seeds being cleaned before they’re packaged and sold for consumption, they still contain trace quantities of opium. Now you may ask,  “how many poppy seeds to test positive?” The old benchmark was 0,3 mcg per ml, but in 1998, the American government revised it and increased the threshold to 2 mcg per ml.

However, some labs still stick with the former threshold. So it depends on what lab testing you decide to follow, but the maximum is 2 mcg per ml. So if you regularly consume poppy seeds, you may test positive for an opiates drug screen.



This is a liquid chemical that rinses/cleanses the entirety of the mouth, including the gums and teeth. It contains an antiseptic. There’s the conventional mouthwash and the detox mouthwash. It inhibits the growth of the oral bacteria that’s responsible for halitosis. Mouthwashes usually contain alcohol (its cleansing agent), and if you’re undergoing a drug screen for alcohol, the test result will be a false positive.

Weight Loss Pills


These medications have consistently been linked with people who failed drug tests but did not smoke. What’s the link? The ingredients, obviously. Some of the ingredients used in manufacturing weight loss pills are very similar in chemical composition to amphetamine. As you know, that’s a substance that’s commonly tested for. If you’re on a weight loss regimen involving pills and you have a tox screen for amphetamine coming up, it will explain why you failed the test.



This oil is also known as Cannabidiol, and it’s the oil extracted from the cannabis plant. This oil is widely used by fitness coaches, athletes, and even regular people for various purposes, such as anxiety relief and pain relief, and to help you sleep better. These oils contain THC. Also, products such as tinctures, weight loss supplements, and even some drinks containing CBD will give the consumer a false positive result for THC screening. This is one of the substances that answers “what can cause a false positive drug test for THC?

ADHD Medications


ADHD (Attention-deficit/hyperactivity disorder) can be treated through either medicine or therapy sessions. Some of the medicines commonly used to treat this disorder include;

  •       Guanfacine
  •       Dexamfetamine
  •       Methylphenidate

The medicines mentioned above, especially methylphenidate is a stimulant drug, and usage of these medications can make you test positive for amphetamines.

Pain or Anti-Inflammatory Medication


These are the same as NSAIDs.

Antipsychotic Drugs


These medications are also referred to as neuroleptics. Their function is to treat and manage psychotic disorders, especially Schizophrenia. This condition can include paranoia, delusions, disordered thoughts, and hallucinations. These medications can cause false positives for a drug screen. Common examples of antipsychotic drugs include;

  •       Clozapine
  •       Paliperidone
  •       Risperidone

Baby Soap


This may sound weird and unexpected, and to be fair, it is. However, even researchers are perplexed as to the reason the use of baby soap causes false positives for a marijuana screen. Some speculated that it could be some of the chemicals in the soap that has a structure similar to THC.

Consequences of False Positives


  •       Loss of employment: False positives are harmful both in the context of a drug test as well as in medical or general science. For the former, a job applicant may lose a prospective job offer because of a false positive test result. It sucks to bear the cross for something you’re not even guilty of. Not all labs conduct confirmatory tests to ascertain if the first was a false positive or not. The same applies to employees working in companies with a zero-tolerance for drug usage. They could lose their job because of false positives. It’s one thing to use drugs or substances and lose your job for that, and it’s another thing not to use and lose your job because your employer thinks you did.
  •       It is bad for healthcare: Because of false positives, many patients have gone through biopsies because the doctor or lab technician saw their test result and assumed there was a particular condition or disease present, whereas it isn’t. What they may be mistaking for something else could simply be a medication, substance, or supplement you used.

How to Dispute a False Positive Drug Test Result?


There are two ways to dispute a false-positive drug test result. The first way is to do it proactively, while the latter is reactive.

  1.     For the proactive dispute – ensure you inform your employer and the lab technician before the test about the medications, products, or supplements you’re currently on. The best way to go about it is to know what the drug test is screening for. From there, you’ll know if the medications, supplements, or products you’re using will cause false positives in your drug test. For instance, if you’re using CBD oil for pain and anxiety relief and undergoing a drug screen for THC, let the relevant parties know before the test. This way, when you test positive, you won’t have to suffer the consequences.
  2.     For the reactive dispute – if you test positive for a substance or drug you know you’re not using, insist on a confirmatory test that will determine whether you’ve actually used those substances/drugs or not.