Drug and alcohol testing is a critical requirement in Department of Transportation (DOT) regulated industries like trucking, aviation, and transit. Many drivers and employees preparing for a test worry about everyday factors: Can stress or diet really affect the outcome of a drug test? This concern is valid, as no one wants to risk a false positive or have their results misinterpreted.

This article breaks down what science, DOT rules, and medical experts say about stress, diet, and test accuracy.

Can Stress Affect Drug Test Results?

Stress itself does not directly cause a positive drug test. Standard drug tests look for specific metabolites of controlled substances, not hormones like cortisol or adrenaline that are linked to stress. However, stress can play an indirect role:

• Physiological Changes: High stress can temporarily affect how your body metabolizes substances. For example, dehydration caused by stress may lead to more concentrated urine, which could make drug levels appear higher.
• Sleep Deprivation: Stress often disrupts sleep patterns. Lack of rest can affect liver function and metabolism, slightly impacting how substances are processed.
• Alter Metabolism: High cortisol levels may affect liver enzymes, changing how quickly substances are broken down.
• Trigger Medication Use: Anxiety and sleep issues often lead people to take antihistamines, sleep aids, or other OTC meds that can cause false positives.

Example: Diphenhydramine (Benadryl) has been known to trigger false positives for PCP in some immunoassay tests.

Can Diet Affect Drug Test Results?

Diet can have a more noticeable effect on drug test results than stress. While what you eat doesn’t introduce illicit substances into your body, certain foods can mimic drug metabolites or interfere with test accuracy.

Key Point:While diet rarely causes a true positive, it can sometimes trigger results that require additional verification by a Medical Review Officer (MRO).

• Poppy Seeds: Consuming foods with poppy seeds may lead to trace levels of opiates being detected.
• Hemp Products: Hemp protein powder or hemp seeds can contain trace amounts of THC.
• Caffeine or Energy Drinks: Excessive use may alter hydration, leading to diluted or concentrated urine samples.
• Grapefruit Juice: Interferes with enzymes that metabolize drugs, possibly altering detection windows.
• Herbal Supplements: Some, like St. John’s Wort, can mimic sedatives or affect metabolism.

Trending in 2025: Vaping & DOT Tests

What About Hydration and Dilution?

Many people think drinking excessive water will “flush” their system. This can actually raise red flags in DOT testing.

• Overhydration -> leads to “dilute specimens.”
• DOT considers diluted urine suspicious. You may be required to retake the test under direct observation.
• Normal hydration is fine, just avoid extreme water intake before your test.

Key takeaway: Stay hydrated, but don’t overdo it. Labs can detect attempts to dilute.

How Employers Ensure Accuracy?

To maintain fairness and accuracy, DOT drug testing and workplace drug testing programs follow strict federal guidelines. This includes:

• Certified Labs: All tests are conducted in SAMHSA-certified laboratories.
• Split-Specimen Testing: If results are questioned, the second portion of the sample can be retested.
• MRO Review: A Medical Review Officer considers prescriptions, diet, and other factors before confirming a positive.

What You Can Do?

If you're preparing for a drug test:

• Avoid poppy seeds and herbal supplements for at least 72 hours.
• Stay moderately hydrated—don’t overdo it.
• Disclose any medications or supplements to the testing administrator.
• Manage stress with sleep, exercise, and mindfulness to avoid unintended medication use.

Final Thoughts

Stress and diet can influence your body in many ways, but they are unlikely to cause a legitimate positive drug test. At most, they may trigger results that need further review. If you’re concerned about medications, supplements, or dietary habits, always disclose this information before your test.

goMDnow specialises in DOT-compliant drug and alcohol testing, consortium services, and return-to-duty testing. Our processes ensure fairness, accuracy, and compliance with federal regulations, giving both employers and employees peace of mind.