Sesame seeds do not contain opiates, cannabinoids, or any other controlled substance that would trigger a positive result on a standard drug test. The confusion, however, is understandable. Sesame seeds are frequently blended with poppy seeds in everything-bagel seasonings and other spice mixes, and poppy seeds are well-documented causes of opiate-positive urine tests. Untangling which seed is actually the problem, and what sesame seeds can and cannot do to your test results, matters if you have a screening coming up.
Where the Confusion Comes From
A case published in the Journal of Analytical Toxicology in 2024 illustrates exactly how the mix-up happens. A chronic pain patient tested positive for codeine during routine urine drug monitoring. She had not taken codeine. What she had done was eat two slices of avocado toast sprinkled with a no-salt seasoning that contained both sesame seeds and poppy seeds. She later tested herself at home with an over-the-counter drug test kit and confirmed that eating the seasoning produced a positive opiate result while skipping it kept her negative.1Journal of Analytical Toxicology. Consumption of seasoning containing poppy seeds can cause codeine positive urine drug test results for pain management monitoring
The critical detail is that the seasoning was not pure sesame. It was a blend, and the poppy seeds in that blend were the source of the positive result. Because the two seeds often appear together in popular seasonings, it is easy for someone to assume the sesame was the culprit. But sesame seeds themselves produce no opioid alkaloids.
Why Poppy Seeds Are the Actual Problem
Poppy seeds come from the opium poppy plant, the same species that produces morphine and codeine. Although the seeds themselves are not psychoactive at the amounts found on a bagel, their surfaces carry trace amounts of these alkaloids from contact with the seed pod during harvesting. When you eat poppy seeds, some of those opiates end up in your urine in measurable quantities.
Research has shown that consuming just 11 grams of poppy seeds, roughly two teaspoons, leads to detectable thebaine, codeine, and morphine in urine. Thebaine concentrations ranged from 2 to 81 nanograms per milliliter in that study.2PubMed. The analysis of thebaine in urine for the detection of poppy seed consumption Larger servings push things further. In a controlled study where participants received two 45-gram doses of uncooked poppy seeds containing roughly 16 milligrams of morphine and 3 milligrams of codeine per dose, urine samples collected over the following 32 hours showed clearly elevated opiate levels.3PubMed Central. Morphine and codeine concentrations in human urine following controlled poppy seeds administration of known opiate content
The opiate content of poppy seeds varies enormously depending on the variety, where they were grown, and how they were processed. Some batches are relatively clean; others carry far more alkaloid residue. That unpredictability is what makes the poppy-seed problem so stubborn for drug-testing programs.
The Federal Cutoff Exists Because of Poppy Seeds
The federal government recognized this problem decades ago. In 1998, the Substance Abuse and Mental Health Services Administration raised the urinary cutoff concentration for morphine and codeine from 300 to 2,000 nanograms per milliliter specifically to reduce false positives from poppy seed consumption. Yet even that higher threshold does not eliminate the risk entirely. Studies have confirmed that poppy seed ingestion can still push urine morphine levels above 2,000 ng/mL.4Journal of Analytical Toxicology. Concentrations of Morphine and Codeine in Paired Oral Fluid and Urine Specimens Following Ingestion of a Poppy Seed Roll and Raw Poppy Seeds
So even after the rules were updated to accommodate normal poppy seed consumption, a generous serving of a poppy-heavy food can breach the cutoff. The avocado toast case described above used a home test kit with a 2,000 ng/mL cutoff, and the patient still tested positive.1Journal of Analytical Toxicology. Consumption of seasoning containing poppy seeds can cause codeine positive urine drug test results for pain management monitoring For anyone facing a workplace or legal drug screening, poppy seeds are worth avoiding for at least 48 to 72 hours beforehand. Sesame seeds, by contrast, require no such caution on their own.
Can Sesame Seeds Affect Drug Metabolism Indirectly?
There is one genuinely interesting, though often overstated, connection between sesame seeds and the way drugs move through your body. Sesame seeds contain a compound called sesamin, a lignan that has been studied for its effects on liver enzymes responsible for breaking down medications.
Laboratory research found that sesamin inhibits CYP2C9, an enzyme involved in metabolizing a range of drugs including certain anti-inflammatory medications. The inhibition involves sesamin forming a complex with the enzyme, but that complex is unstable, breaking down within about 30 minutes after the metabolism stops. The researchers concluded that the practical effect of sesamin on CYP2C9-mediated drug metabolism is likely small.5PubMed Central. Influence of sesamin on CYP2C-mediated diclofenac metabolism: in vitro and in vivo analysis
A separate study found that sesamin also inhibits CYP3A4, the single most important drug-metabolizing enzyme in the body, responsible for processing roughly half of all commonly prescribed medications. Sesamin blocks CYP3A4 induction in a dose-dependent manner, and the researchers suggested this could have implications for drug safety when sesame consumption is high.6PubMed Central. Sesamin: A Naturally Occurring Lignan Inhibits CYP3A4 by Antagonizing the Pregnane X Receptor Activation
What does this mean for drug testing? In theory, if sesamin slows down the enzymes that break down a medication you are already taking, the drug could stay in your system longer and at higher concentrations than expected. That could, in a narrow set of circumstances, make a prescribed medication show up at a higher level on a test than your clinician anticipates. But this is a very different thing from “sesame seeds make you fail a drug test.” It is not creating a false positive for a substance you never consumed. It is a theoretical pharmacokinetic interaction, and the real-world evidence for it causing drug test problems in people eating normal amounts of sesame is essentially nonexistent. If you take medications that are cleared by CYP3A4 and you eat sesame-heavy dishes regularly, it is worth mentioning to your pharmacist, but that is a drug interaction conversation, not a drug test conversation.
Other Seeds and Foods That Can Cause Real Problems
Poppy seeds are the most infamous food-based cause of false positive drug tests, but they are not the only one. Hemp seeds are a relevant comparison because they are also widely consumed in health foods and come from a plant associated with a controlled substance.
In one study, volunteers who ate commercially available snack bars made from pressed hemp seeds had urine specimens that screened positive for marijuana using an immunoassay at a 20 ng/mL cutoff. Those who ate three cookies made from hemp seed flour and butter had specimens that tested positive at both 50 and 20 ng/mL cutoffs. However, when confirmatory testing was performed with more precise methods, the results failed to meet reporting criteria, meaning the levels of the specific marijuana metabolite were too low to be officially reported as positive.7PubMed. Marijuana-positive urine test results from consumption of hemp seeds in food products
A more recent study with Korean hemp seed products found that normal consumption over both short-term (one week) and long-term (twelve weeks) periods did not produce positive cannabinoid results. Out of 480 urine samples in the long-term study, only 3 from 2 participants showed levels above the detection cutoff, and all of those were negative on the screening test.8PubMed. Analysis of cannabinoids in urine samples of short-term and long-term consumers of hemp seed products The difference likely reflects improvements in how hemp seeds are processed and how well modern products control for THC contamination. Still, the older study demonstrates that the risk is not zero, particularly with artisanal or less-regulated hemp products.
Beyond seeds, a number of other foods and over-the-counter products can interfere with drug tests. Tonic water contains trace amounts of quinine, which can cross-react in some older opiate assays. Certain herbal teas made from coca leaves, legal in parts of South America but uncommon elsewhere, can produce cocaine metabolites in urine. Even ibuprofen was once known to cause false positives for marijuana on older immunoassays, though modern tests have largely resolved that issue.
How Drug Tests Work and Why Seeds Fool Them
The standard workplace drug screening uses an immunoassay, a test that relies on antibodies designed to bind to a target drug or its metabolites. Immunoassays are fast and cheap, which is why they are used for initial screening. Their weakness is that the antibodies are not perfectly specific. They can cross-react with structurally similar molecules, which is exactly what happens when morphine from a poppy seed bagel meets an opiate antibody test.
When a screening immunoassay comes back positive, the sample is supposed to be sent for confirmatory testing using a more precise technique, typically mass spectrometry. This second-tier test can distinguish between specific compounds and their concentrations, making it much harder for a poppy seed to masquerade as heroin use. In a properly run testing program, the confirmatory test should catch a food-related false positive. But not every testing program follows best practices, and the initial positive can still trigger consequences, including being pulled from a job site, flagged in a pain management program, or required to explain yourself to a medical review officer.
Sesame seeds simply do not produce any compounds that these antibodies recognize. There is no morphine, codeine, THC, amphetamine, or any other drug-class molecule in sesame seeds. The immunoassay has nothing to latch onto. That is the fundamental difference between sesame and poppy, and it is why sesame seeds alone will never produce even a preliminary positive screening result.
The Everything-Bagel Problem
The practical difficulty is that most people do not eat sesame seeds in isolation. They eat everything bagels, everything seasoning, tahini-topped dishes at restaurants that also use poppy seeds, and mixed-seed crackers. The trend toward everything-seasoning in recent years has spread poppy seeds far beyond their traditional niche in baking. You can now find poppy-sesame blends on avocado toast, roasted vegetables, salads, and even popcorn.
If you are not thinking about which seeds are on your food, and most people are not, it is easy to attribute a positive test to the wrong ingredient. The avocado toast case is a perfect example. The patient’s first instinct was to note the seasoning, but the specific component doing the damage was the poppy seed fraction, not the sesame. In fact, the case itself was published partly to remind clinicians that commercially available seasonings containing even small amounts of poppy seeds can cause clinically relevant opiate-positive urine results.1Journal of Analytical Toxicology. Consumption of seasoning containing poppy seeds can cause codeine positive urine drug test results for pain management monitoring
If you are facing a drug test and want to play it safe, the rule of thumb is straightforward: avoid poppy seeds for at least two to three days beforehand. Read ingredient labels on spice blends and seasonings. Sesame on its own, whether as tahini, sesame oil, whole toasted seeds, or halva, is fine. The moment poppy seeds enter the picture, the risk changes.
What to Tell Your Doctor or Medical Review Officer
If you do test positive for opiates and believe it was caused by food, the first step is to tell the person reviewing your results exactly what you ate and when. In federally regulated testing programs, a medical review officer, typically a licensed physician with specialized training, is responsible for interpreting positive results before they are reported to an employer. Their job includes evaluating whether a legitimate explanation exists.
Poppy seed ingestion is a well-recognized cause of true-positive (not technically “false” positive, since the morphine is genuinely present) opiate results, and medical review officers are trained to investigate it. The key analytical marker they look for is the ratio of morphine to codeine in the sample, along with the presence or absence of other metabolites like thebaine and papaverine that show up after poppy seed consumption but not after heroin or prescription opioid use. If your urine contains morphine and codeine in a ratio consistent with poppy seeds, and thebaine is present, that strongly suggests dietary exposure rather than drug abuse.
Sesame seeds do not produce any of these markers. If your test result shows opiates and you only ate sesame, something else is going on. Either the product you ate also contained poppy seeds, you were exposed to an opiate through another route, or there is a different source of cross-reactivity that needs investigation.
Sesamin Supplements and Concentrated Doses
While dietary sesame is not a drug test concern, it is worth noting that sesamin is sold as a standalone supplement, often marketed for fat loss, antioxidant benefits, or cholesterol support. Supplement capsules can deliver far more sesamin than you would get from a tablespoon of tahini, and the enzyme-inhibiting effects seen in lab studies become more plausible at higher doses.
The CYP3A4 inhibition documented in research was dose-dependent, meaning more sesamin produced a greater effect on the enzyme.6PubMed Central. Sesamin: A Naturally Occurring Lignan Inhibits CYP3A4 by Antagonizing the Pregnane X Receptor Activation If you are taking a medication metabolized by CYP3A4, which includes many statins, calcium channel blockers, certain anti-anxiety drugs, and immunosuppressants, a high-dose sesamin supplement could theoretically slow the clearance of that drug from your body. The drug itself would not appear on a standard drug-of-abuse panel, but in contexts where specific drug levels are being monitored, an unexpectedly high reading could raise questions.
The CYP2C9 interaction, while real in laboratory conditions, appears to be weaker in practical terms. The molecular complex between sesamin and the enzyme broke down quickly, leading researchers to conclude that the real-world impact on drug metabolism is probably minimal.5PubMed Central. Influence of sesamin on CYP2C-mediated diclofenac metabolism: in vitro and in vivo analysis For someone eating normal amounts of sesame seeds in food, neither of these enzyme effects is likely to matter. For someone taking concentrated sesamin supplements alongside prescription medications, a conversation with a pharmacist is a reasonable precaution.
How Poppy Seed Alkaloid Content Varies
One reason poppy seed drug test problems persist despite the raised federal cutoff is the enormous variability in alkaloid content from batch to batch. Poppy seeds sold at grocery stores are food-grade, but the amount of morphine and codeine clinging to their surfaces can differ by a factor of 100 or more between brands or even between lots from the same supplier. A lemon poppy seed muffin made with one brand might be completely benign, while the same recipe made with another brand’s seeds might push you over the testing threshold.
The controlled dosing study that gave participants 45 grams of poppy seeds with known morphine content (about 16 milligrams per dose) produced easily detectable urinary opiates.3PubMed Central. Morphine and codeine concentrations in human urine following controlled poppy seeds administration of known opiate content But a consumer buying poppy seeds off a grocery shelf has no way of knowing how much morphine is in their purchase. Labels do not disclose alkaloid content. Washing poppy seeds before use, a step recommended by some food safety authorities, can reduce but not eliminate the surface alkaloids.
This variability is a good reason to take a blanket-avoidance approach before a drug test rather than trying to calculate a “safe” amount. There is no safe amount you can be confident in without laboratory analysis of the specific batch of seeds you are eating.