Impairment vs. Under the Influence – Impairment and Drug Testing

– Bill Current is the President and Founder of the Current Consulting Group, LLC

 This information is provided for educational purposes only. Reader retains full responsibility for the use of the information contained herein.

With the legalization of marijuana in many states (11 for recreational use and 34 for medicinal use), the subject of impairment identification has become a hot topic. Why? Primarily because the proponents of legalization argue that:

  1. if smoking marijuana is legal, but
  2. being at work impaired by marijuana is not, but
  3. a drug test result does not prove impairment—then why drug test?

(Note: Of course, this line of reasoning assumes that the only reason to conduct drug testing is to identify employees who are impaired and ignores one of the greatest benefits of drug testing, which is deterrence.)

Impairment and Drug Testing

Drug testing professionals long-ago conceded that a positive drug test result does not mean a donor was impaired at the time urine, oral fluid or hair sample was collected. However, the donor clearly was impaired at some point after using marijuana (or any of the other substances for which employers commonly test). We know this because numerous studies and reports conclusively show that, for some period of time after usage, marijuana impairs a user’s short-term memory, thinking and problem-solving capabilities, body movement and reaction time, and coordination (such as the ability to safely drive a motor vehicle).[i]

Differences: Impairment and Under the Influence

There is another term that is often used interchangeably with impairment, and that is “under the influence.” But the two terms refer to different things and can be applied to a drug-free workplace policy separate from one another.

Impairment can be defined by the dictionary. For example, according to, impairment means “the state or condition of being impaired: diminishment or loss of function or ability.”[ii] Under the influence, on the other hand, is usually a legal term defined differently depending on the specific law being applied. For instance, most states define “driving under the influence” (DUI) as exceeding a legally established measurement of alcohol in a driver’s system (0.08 Blood Alcohol Content (BAC) is the federal standard). When someone tests at or above that specified BAC, they are legally considered to be under the influence and driving while intoxicated or driving while impaired.

Even though some state drug testing laws and legal marijuana laws use the words impair or impairment, for policy purposes employers should avoid those words and instead lean more toward “under the influence” as defined by the company (unless an applicable state law defines the term). For instance, a company policy can define “being under the influence” as exhibiting the signs and symptoms of substance abuse, including consistently poor job performance, excessive absenteeism and a positive drug test result. The policy is not suggesting the positive test result is proof of impairment, but rather a violation of the company’s policy of being at work while under the influence as demonstrated by, among other things, a positive drug test result.


Always carefully review any applicable state drug testing laws and ensure complete compliance. Most state laws either do not use the word impairment or the term under the influence or attempt to define them. This creates an opportunity for a company to be as specific and detailed as possible when making the connection between an employee’s on-the-job behavior and a drug test result. And remember, adverse employment action can be based on consistently poor and well-documented job performance with a positive drug test result being the final factor rather the entire reason for termination.

© 2010-2020 The Current Consulting Group, LLC – No portion of this article may be reproduced, retransmitted, posted on a website, or used in any manner without the written consent of the Current Consulting Group, LLC. When permission is granted to reproduce this article in any way, full attribution to the author and copyright holder are required.

[i] National Institute on Drug Abuse. Drug Facts: Marijuana.

[ii] Merriam-Webster.

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