Understanding Drug Tests and False Positives
Workplace and medical drug screenings are designed to detect specific illicit and prescription substances. The most common initial test is an immunoassay, which is fast and cost-effective [1.14.1]. However, these tests can sometimes produce a "false positive" result. This happens when the test detects a substance with a similar chemical structure to the target drug, a phenomenon known as cross-reactivity [1.6.2]. While most common herbal teas like chamomile, ginger, or standard peppermint are safe and do not contain compounds that would trigger a positive result, a few specific types of herbal teas and supplements pose a risk [1.5.4, 1.5.3]. It's important to understand which teas carry this risk and the pharmacological reasons behind it.
Herbal Teas That Can Cause a Positive Drug Test
Certain teas contain active compounds that are either identical to or structurally similar to drugs targeted in screenings. Consumption of these teas can lead to a positive result, which may be a true positive (the drug is present) or a false positive (cross-reactivity) depending on the tea and the test.
Coca Tea
Coca tea, made from the leaves of the coca plant, is popular in South American countries like Peru and Bolivia [1.3.1, 1.9.3]. The coca plant is the same source from which cocaine is derived. Therefore, drinking coca tea will lead to a genuinely positive test for cocaine because it introduces cocaine alkaloids into your system [1.9.1]. Studies have shown that consuming a single cup of coca tea can result in detectable levels of cocaine metabolites in urine for at least 20 to 36 hours [1.9.1, 1.4.1]. The U.S. Department of Transportation does not consider coca tea consumption a legitimate medical explanation for a positive cocaine test [1.9.3].
Poppy Seed Tea
Poppy seeds are harvested from the opium poppy plant, the source of opiates like morphine and codeine [1.8.3]. While the seeds themselves are not supposed to contain opium, they can become contaminated with opiate residue during the harvesting process [1.8.3]. Consuming poppy seed tea, which often involves washing or brewing large quantities of seeds, can lead to significant concentrations of morphine and codeine in the body, resulting in a positive test for opiates [1.8.1]. A person can test positive for up to 48 hours after ingestion [1.8.2]. In response to this issue, many official testing guidelines, such as those from the Department of Health and Human Services, raised the cutoff threshold for opiates to 2,000 ng/mL to better distinguish routine dietary consumption from drug use [1.8.3].
CBD (Cannabidiol) and Hemp Tea
CBD is a non-psychoactive compound found in the cannabis plant. While CBD itself is not what drug tests screen for, products made from hemp (which includes CBD teas) can legally contain trace amounts of THC (tetrahydrocannabinol), the psychoactive component of marijuana, up to 0.3% [1.10.1, 1.10.2]. Standard drug tests detect THC [1.5.4]. Frequent consumption of full-spectrum CBD products or use of mislabeled products with higher-than-advertised THC levels can lead to a buildup of THC in the system, potentially causing a positive drug test [1.10.1, 1.10.3]. Because the CBD market is not consistently regulated for safety and purity, the risk of contamination or mislabeling is a significant concern [1.10.2].
Other Herbal Supplements of Concern
While less commonly consumed as teas, some herbal supplements have been linked to false positives:
- Kava: Has been associated with false positives for benzodiazepines [1.3.4].
- St. John's Wort: May interfere with assays for THC and antidepressants [1.12.1].
- Ginseng: Could potentially affect amphetamine screenings [1.13.2].
- Echinacea: Has been reported in some cases to trigger false positives for THC [1.3.4].
Comparison of High-Risk Herbal Teas
| Herbal Tea/Supplement | Active Compound(s) of Concern | Drug Detected on Test | Type of Result |
|---|---|---|---|
| Coca Tea | Cocaine, Benzoylecgonine [1.9.1] | Cocaine | True Positive |
| Poppy Seed Tea | Morphine, Codeine [1.7.3, 1.8.1] | Opiates | True Positive |
| CBD/Hemp Tea | Tetrahydrocannabinol (THC) [1.10.1] | THC (Marijuana) | True Positive (if THC is present) |
| Kava | Kavalactones (cross-reactive) [1.11.3, 1.3.4] | Benzodiazepines | False Positive |
| St. John's Wort | Hyperforin/Adhyperforin (cross-reactive) [1.12.1] | THC, Antidepressants | False Positive |
The Role of Confirmatory Testing
If you receive a positive result from an initial screening test that you believe is false, it's crucial to take immediate action. The standard procedure following a non-negative initial test is a second, more specific confirmatory test [1.6.3]. This is typically done using Gas Chromatography-Mass Spectrometry (GC-MS) or Liquid Chromatography-Mass Spectrometry (LC-MS) [1.14.3].
GC-MS is considered the "gold standard" for drug testing because it separates substances in the sample and provides a unique "chemical fingerprint" for each one [1.14.1, 1.14.2]. This high level of precision can distinguish between the actual drug and a cross-reactive compound from an herbal product, thereby eliminating false positives [1.14.1]. For example, a GC-MS test would not produce a false positive for THC due to St. John's Wort [1.12.2]. If you face a positive result, you should disclose any herbal teas or supplements you have been taking and request a confirmatory test [1.6.2, 1.6.4].
Conclusion
In conclusion, while the vast majority of herbal teas on the market pose no risk for drug testing, a few specific varieties can cause a positive result. Coca tea and poppy seed tea can produce true positives for cocaine and opiates, respectively, because they contain the actual drug alkaloids. CBD and hemp teas can lead to a positive test for THC if the product contains sufficient quantities of this compound. Other supplements like kava and St. John's Wort may cause false positives on initial screenings due to cross-reactivity. If faced with an unexpected positive result, transparency about supplement use and insisting on a GC-MS confirmatory test are the best steps to prove the result was not due to illicit drug use.
For more information on drug testing procedures, you can visit an authoritative source like the Substance Abuse and Mental Health Services Administration (SAMHSA).
