Can a drug test show if I am taking more of a prescription drug than my doctor told me to take?

By Suzanne Ball | Last updated: January 17, 2019

The exact name and amount of a prescription drug that cause a positive test result are not detected with a drug screen. However, with the over 15 million people abusing prescription drugs, (Learn more in "A Look At Prescription Drug Abuse Statistics".) employers are choosing to screen for more substances beyond the standard 5 Panel test: THC (marijuana), cocaine, amphetamines, PCP, and opiates. (Learn more in "Drug Abbreviations Used in Drug Testing".) Physicians can also prescribe benzodiazipines (Xanax) and oxycodone (Oxycontin). By using a 7 Panel test, these can also be detected.

If any panel has a positive result, the sample is sent for confirmatory testing, performed using sophisticated methods. The results are reviewed by a Medical Review Officer (MRO) who works independently from the laboratory and the employer, in order to remain impartial and to provide confidentiality.

If a prescription drug level is at or higher than the accepted cut-off level, the specified amount to be considered as positive, the MRO can contact the person for an explanation. (Learn more in "Drug Detection Cutoffs: What You Need to Know".) If the person can provide a verifiable explanation for use of the medication, the MRO can report the result as negative. However, if the person’s job is safety-sensitive or the use of the drug (even with a prescription) could put others at risk, the MRO can document the result as “negative, with safety concerns.”

Prescription drug usage can generally be detected in urine samples for the following amount of time:

  • Amphetamines – 48 hours
  • Barbiturates – 2-10 days
  • Benzodiazepines – 2-3 weeks
  • Hydrocodone – 2-4 days
  • Morphine – 2-3 days
  • Methadone – 2-3 days

It is important for employers to know that drug screening does not always indicate current drug use or the quantity of the substance taken. Factors such as age, weight, amount of body fat, metabolic rate, and overall health can affect test results.

The ADA has determined that asking an employee about prescription drugs is a “disability-related inquiry” and can be cause for discrimination. Questions may only be related to the specific job function and for business necessity, according to the EEOC.

A robust drug-free workplace program, with well-written policies can protect a company from liability and litigation. Seek legal advice for any issues involving possible discrimination. (Learn more in "The Importance of a Good Drug and Alcohol Policy in the Workplace".)

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Written by Suzanne Ball

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Suzanne Ball is an experienced Registered Nurse with a Masters Degree in Health Sciences. She has worked in a variety of settings, including acute care, quality improvement, and research. She is a freelance writer who specializes in writing about medical and health topics.

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