When does the Department of Transportation (DOT) permit blood drug testing?

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Last updated: March 25, 2025 • View editorial policy

From the Research

The Department of Transportation (DOT) permits blood drug testing only in very limited circumstances, such as post-accident situations where the employee is unconscious or unable to provide a breath or urine sample, as supported by the most recent study 1.

Background

The use of blood drug testing by the DOT is subject to strict regulations and guidelines. According to the study published in 2023 1, blood testing is allowed primarily when breath alcohol testing is not available or when a breath test cannot be performed.

Key Points

  • Blood testing is relatively rare due to its invasive nature and the requirement for medical personnel to collect samples.
  • The detection windows for substances in blood are different compared to urine or breath testing.
  • Employers and testing facilities must ensure they are following current DOT regulations before conducting any blood tests, as unauthorized testing could violate employee rights and regulatory requirements.
  • The study published in 2023 1 highlights the importance of following strict chain-of-custody procedures and analyzing blood samples at certified laboratories.

Medical Considerations

  • The DOT prefers breath testing for alcohol and urine testing for drugs, making blood testing a less common option.
  • Blood testing may be permitted in specific medical situations where other testing methods are not feasible, or when directed by a Medical Review Officer (MRO) as part of a medical evaluation.
  • The study published in 1996 2 emphasizes the importance of occupational health nurses in the commercial drivers' license screening process and their role in assisting employers with compliance with federally mandated regulations.

Regulatory Considerations

  • The Omnibus Employees Testing Act of 1991 mandated rules and regulations on drug and alcohol testing for employees in "safety sensitive" positions.
  • The study published in 2000 3 discusses the choice between blood- and breath-alcohol analysis for forensic purposes and the factors that influence this decision.
  • The study published in 2012 4 provides an overview of alcohol testing and interpretation in the 21st century, including the pharmacokinetics of ethanol and the methods for detecting ethanol in body fluids.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.