You’ve probably heard “You are what you eat,” but when it comes to urine drug tests, it’s more like “You are what you consume.” Ever wondered why you or someone else tested positive for THC (the cannabis high compound)? This is where you’ll find out.

What Can Cause a Positive THC Urine Test?

This article will explore what can cause a positive THC urine test and what happens if you fail a drug test.

Understanding False Positive Drug Tests

A false positive in a drug test happens when it wrongly shows a substance someone didn’t use. They’re not rare, with estimates of about 5-10% false positives and about 10-15% false negatives. These mistakes can cause job loss or legal problems, so knowing what triggers them is crucial to avoid trouble.

Some of the commonly screened drugs include:

  • Benzodiazepines
  • Cocaine
  • Opioids
  • Marijuana (THC)
  • Alcohol
  • Barbiturates
  • Amphetamines
  • Phencyclidine (PCP)

Consequences of False Positive Drug Test Results

The consequences of false positive results may include:

  1. Job Loss: False positive drug tests can lead to immediate termination or work suspension due to employers’ strict drug-free policies.
  2. Reputation Damage: Positive drug test results can stain an individual’s reputation, challenging future job prospects.
  3. Legal Issues: A false-positive drug test may result in liability in workplace accidents, even if the individual was not impaired during the incident.
  4. Benefits Loss: False positive drug tests can lead to the loss of healthcare benefits, government assistance, or child custody disputes.
  5. Emotional Impact: False positive results can cause severe stress, anxiety, and emotional distress due to the fear of job loss and legal consequences.

You might wonder, “What can cause a false positive for THC in urine drug screen?” While THC tests are generally reliable, certain medications and substances like NSAIDs, promethazine, riboflavin, dronabinol, ethacrynic acid, and certain synthetic cannabinoids can sometimes trigger a false positive on a THC urine drug test.

Types of Drugs Tested

Many types of drugs are commonly screened for in drug tests:

  • Amphetamines
  • Alcohol
  • Barbiturates
  • Cocaine
  • Benzodiazepines
  • Propoxyphene
  • Methadone
  • Marijuana metabolites
  • Morphine
  • Heroin
  • Methamphetamine
  • Hydrocodone
  • Oxycodone
  • Phencyclidine

It is crucial to know that drug tests can reveal recent drug use but don’t diagnose addiction. A thorough evaluation by a healthcare expert or licensed alcohol and drug counselor is necessary for an accurate addiction diagnosis.

Does Alcohol Show Up on a Drug Test for Work?

Generally, alcohol doesn’t pop up on regular work-related drug tests. They usually focus on other substances. However, if there’s a workplace accident or legal situation, alcohol testing may come into play. So, for most job-related drug tests, you won’t need to worry about your last night’s drink.

Use and Misuse

Positive THC urine tests can often be attributed to two main factors: the use of illegal substances and the misuse of prescription medications.

Using Illegal Substances: The main reason for a positive THC urine test is using illegal substances, especially marijuana. When you vape, smoke, or consume cannabis in any way, your body processes THC, and it can appear in your urine for a while.

Misusing Prescription Medications: Another very common cause of positive THC urine tests is the misuse of prescription medications. Some prescription drugs, like Marinol, contain synthetic forms of THC. If taken without a valid prescription or not as directed, these medications can lead to a positive THC test result. It’s crucial to follow your healthcare provider’s instructions carefully when using prescription medications to avoid unexpected outcomes on drug tests.

Can Second Hand Smoke Make You Fail A Drug Test?

Yes, exposure to secondhand cannabis smoke can introduce small THC amounts into your system. While it’s less likely to make you fail a drug test compared to direct use, it’s not impossible. If you’ve been around a lot of secondhand cannabis smoke before a drug test, inform the testing provider for an accurate interpretation of your results.

Objectives of Drug Testing

Drug testing serves various purposes across different domains, reflecting the diverse reasons behind its widespread use.

Employment: In the workplace, drug testing is most common. Employers may require drug screening before hiring an applicant, during employment (randomly or periodically), when there are suspicions of drug use based on observed signs and symptoms, or after workplace accidents or incidents.

Sports: Athletes, especially professionals, undergo drug testing to screen for substances that may enhance performance, ensuring fair competition.

Treatment with Drugs: Drug testing plays a vital role in diagnosing, treating, and monitoring individuals with alcohol use disorder and substance use disorder. It helps assess treatment adherence, monitor abstinence, and detect early relapse, often used in court-ordered treatment programs or probation.

Evidence in Court: Drug testing is used in legal contexts, such as collecting potential evidence of a crime, investigating child abuse or endangerment cases, and determining impairment due to alcohol or other substances while driving.

Monitoring Prescription Drug Abuse: Healthcare providers may request drug tests to monitor patients taking prescription drugs with high addiction potential or misuse risk, like opioids for pain management.

Understanding the objectives of drug testing underscores its significance in various facets of life, from employment to healthcare and the legal system.

Interference with Drug Testing

  1. NSAIDs (Nonsteroidal Anti-Inflammatory Medications): Common OTC NSAIDs like Ibuprofen and Naproxen can sometimes trigger false positives for barbiturates or THC. Oxaprozin, another NSAID used for pain, may result in a false positive for benzodiazepines.
  2. Antibiotics: While most antibiotics don’t interfere with drug screens, Rifampin, used to treat tuberculosis, may show up as opiates in certain rapid urine screens, even long after ingestion.
  3. Antidepressants: Some antidepressants can cause false positives. For instance, Quetiapine may incorrectly indicate methadone use, while Chlorpromazine can lead to a false positive for amphetamine.
  4. Proton Pump Inhibitors (PPIs): Pantoprazole, a PPI used for GERD and heartburn, may cause false positives for THC.
  5. Contrast Media: These substances can interfere with several lab assays, including creatinine, magnesium, selenium, and total iron binding capacity assays.
  6. Biotin: Biotin supplements can significantly interfere with certain lab tests, potentially leading to incorrect results.
  7. Antihistamines: Over-the-counter allergy and sleep medications containing diphenhydramine can show up as methadone or PCP on drug screens.
  8. Vitamin B12: Large doses of vitamin B12 can result in false positives for amphetamines.
  9. Energy Drinks: Some energy drinks with caffeine and amino acids can trigger false positives due to structural similarities with certain drugs.
  10. Kava: Although known for its relaxation properties, kava can cross-react with amphetamine immunoassays, leading to false-positive results.

Being aware of these potential interferences can help individuals and healthcare professionals interpret drug test results accurately, preventing unnecessary concerns or consequences.

Food and Supplements That Show Up on Drug Tests

Some foods, supplements, and even poppy seeds can cause a positive THC urine test, leading to confusion. Hemp seeds, hemp oil, certain herbal teas, and poppy seeds contain trace THC amounts, potentially triggering a false positive result. To avoid surprises, inform your testing facility if you regularly consume this food. Staying mindful of your diet can help prevent unexpected outcomes on your drug test.

How Many Poppy Seeds to Test Positive for Opiates

Curious about poppy seeds? Well, it turns out that just a small amount can lead to a positive test for opiates. Eating a poppy seed can produce an opiate level of about 250 ng/ml after three hours. Eating just three teaspoons of poppy seeds can lead to a level of 1,200 ng/ml in six hours. Even a small amount of poppy seeds can affect your drug test results.

Will Phentermine Show Up on a Drug Test for Work?

Phentermine, a medication similar to amphetamines, might trigger a false positive if you’re not using it for a valid medical purpose, like ADHD treatment. So, be cautious if you’re taking phentermine and facing a drug test at work.

How To Dispute A False Positive Drug Test

So, you’ve taken a urine drug test, and it came back positive for THC, despite not using marijuana. It can be frustrating and concerning but don’t worry – false positive results can happen.

Here’s what you can do to dispute a false positive drug test:

  1. Request a Follow-up Test: If you believe the result is incorrect, ask for a follow-up test. Follow-up testing is crucial to resolve the issue. This could involve a more accurate and comprehensive lab test that can distinguish between false positives and actual drug use.
  2. Check Medications: Certain medications and supplements can trigger false positive THC results. Inform your testing facility about any medications you’re taking to rule out this possibility.
  3. Review Your Diet: Some foods, like hemp seeds or certain herbal teas, contain trace amounts of THC. A large intake of these items could potentially lead to a false positive. Be mindful of your diet before the test.
  4. Lab Errors: Laboratories aren’t infallible. Mistakes can occur during the testing process, so it’s essential to verify the accuracy of your test results.
  5. Consult an Expert: Don’t hesitate to discuss the situation with your healthcare provider. Share any medications, supplements, or substances you’ve been using to help them understand the potential causes of the positive result. Your doctor can guide you through the next steps and potentially request additional testing or documentation to support your case.
  6. Legal Recourse: False positive results can sometimes have serious consequences. Consult with an attorney specializing in drug testing issues if your situation involves legal implications.

How To Explain Failed Drug Test?

  1. Be honest about the situation.
  2. Provide proof of any valid prescriptions.
  3. Describe any exposure to substances.
  4. Request a retest if possible.
  5. Remain professional and respectful.
  6. Follow company policies.
  7. Seek legal advice if needed.

Frequently Asked Questions

1. Do poppy seeds make you fail a drug test?

Yes, poppy seeds, often used in baking and cooking, may contain trace amounts of opiate residue. Consuming them can result in a positive opiate test, which lab analysis confirms as morphine.

2. What causes a positive urine screening?

Urine screenings can yield false positives, often due to the use of poppy seeds, CBD, or certain over-the-counter (OTC) and prescription medications. These substances may have similarities with the drugs the test aims to detect.

3. What should I do if I get a false positive result?

If you suspect a false positive on a urine drug test, consider your medications. Discuss it with your healthcare provider, who may run a more specific confirmation test, reducing the risk of false positives.

4. What OTC medications can cause a false positive for methamphetamines?

Several OTC medications can lead to false positive results for methamphetamines, including dextromethorphan (a cough suppressant), diphenhydramine (an antihistamine), certain decongestants, NSAIDs, and some antidepressants.

5. Does CBD show up on a drug test pee?

CBD itself doesn’t show up on a drug test. However, some CBD products with low levels of THC might, in theory, result in a positive test.


Understanding the factors that can cause a positive THC urine test is crucial, as it can have substantial consequences in various aspects of life, including employment, reputation, and legal matters. These errors can result from various sources, such as medications, substances, and even dietary choices.

It’s essential to be aware of these potential interferences and take appropriate steps if you encounter a false positive result.