According to separate data from Employers, a small-business insurance company, 10 percent of small businesses reported that employees showed up in 2013 under the influence of at least one controlled substance, with marijuana coming in at 5.1 percent.
Marijuana sales overall are taking off as recreational use of cannabis is legal in Colorado and Washington state, and pot can be purchased for medicinal use in 23 states and Washington, D.C.
So what's an employer to do?
Companies have different strategies and opinions on testing. But the vast majority of U.S. employers aren't required to test for drugs. According to the U.S. Department of Labor, many state and local governments have statutes that "limit or prohibit workplace testing, unless required by state or Federal regulations for certain jobs."
Private employers, for the most part, can test for a wide variety of substances, according to the Labor Department.
Smaller businesses, meanwhile, with limited resources to test employees are in the early stages of figuring out next steps. Even in places like Colorado where recreational cannabis use is legal, employers are trying to strike a balance between respecting the law and establishing clear workplace rules.
Read MoreLegal use of marijuana clashes with job rules
Christopher Myers, co-founder of BodeTree, a 15-employee start-up based in Denver, says he has yet to create a policy strictly for marijuana use in the workplace.
As an online service that helps small businesses manage and understand their finances, BodeTree has to comply with financial institutions' policies for protecting client data. Myers said there's a zero tolerance policy when it comes to substance use on the job.
"It's an interesting balance, because we need a policy that is compliant with federal and state law," he said. "And we are respectful of those laws. But we don't want someone showing up to work drunk, on Vicodin or high on marijuana."
For now, Myers isn't performing spot testing for marijuana consumption on employees.
"The testing technology in Denver will detect if you have been using marijuana in the past 30 days," he said. "From a policy point of view, no one knows how to handle it."