Missouri drug testing laws for employers: pre-employment testing rules (2026)

Missouri has no statute that sets procedures for private-employer drug testing, so employers may test job applicants under their own written policy. The real limit is constitutional: Article XIV, section 1.7(15) of the Missouri Constitution bars refusing to hire a valid medical marijuana cardholder because of their card or a positive marijuana test, unless they used or were impaired at work, or the job is safety-related, conflicts with a bona fide occupational qualification, or hiring would cost a federal benefit. The 2022 adult-use amendment adds no hiring protection for recreational users, as of October 2026.

Missouri drug testing rules at a glance

Does Missouri have a drug testing law for employers?

Not a general one. Missouri has no counterpart to Minnesota's testing act or Mississippi's opt-in testing chapter: no required notice form, laboratory standard, confirmation step or retest right for private employers. That means three things decide how you test in Missouri:

• Your written policy. It is what you will point to if a decision is challenged, and Missouri's workers' compensation law rewards having one (see below).
• The Constitution's medical marijuana protections, which limit what you may do with a positive THC result.
• Federal rules for DOT-regulated jobs and federal contractors.

Because the state sets no procedure, adopt one anyway. A practical baseline, borrowed from federal practice rather than required by Missouri law: test after a conditional offer, test everyone offered the same position the same way, use an HHS-certified laboratory, have positives confirmed and reviewed by a medical review officer, and let the candidate explain a positive before you withdraw the offer.

What does Missouri's Constitution say about medical marijuana and hiring?

Missouri voters added medical marijuana to the Constitution, so the hiring rule is in Article XIV, section 1, not in a statute. Section 1.7(15) says that, unless failing to do so would cause the employer to lose "a monetary or licensing-related benefit under federal law," an employer "may not discriminate against a person in hiring, termination or any term or condition of employment or otherwise penalize a person" based on either:

1. the person's status as a qualifying patient or primary caregiver with a valid identification card, including "legal use of a lawful marijuana product off the employer's premises during nonworking hours," unless the person was under the influence on the premises or during the hours of employment; or
2. "a positive drug test for marijuana components or metabolites" of a person with a valid qualifying patient card, unless the person used, possessed or was under the influence on the premises or during the hours of employment.

The same subsection lists who is not covered:

• an employee "in a position in which legal use of a lawful marijuana product affects in any manner a person's ability to perform job-related employment responsibilities or the safety of others"; and
• a position where use "conflicts with a bona fide occupational qualification that is reasonably related to the person's employment."

Section 1.7(1)(d) closes the loop: the section does not let anyone sue an employer for prohibiting work under the influence, or for disciplining someone, up to termination, "for working or attempting to work while under the influence of marijuana." The Department of Health and Senior Services' Division of Cannabis Regulation issues the patient cards.

In practice: decide before you post the job whether it is a safety or performance position under section 1.7(15), write that down, and train recruiters not to reject a cardholder for a THC-positive pre-employment result in any other job.

Does Missouri's adult-use law protect job applicants?

Not expressly. The adult-use amendment, Article XIV, section 2, effective December 8, 2022, makes marijuana legal for adults 21 and older. Its employer clause, section 2.3(3), says the section "does not require an employer to permit or accommodate" marijuana "in any workplace or on the employer's property," does not stop discipline for working while under the influence, and does not prevent refusing to hire or other adverse action "because that person was working while under the influence of marijuana." Section 2 has no clause like section 1.7(15) protecting an adult-use consumer who is not a cardholder. Section 2.3(2) keeps the medical protections in section 1 in force.

The result: a positive THC result from a candidate who is not a medical cardholder can be treated under your policy like any other positive. A cardholder's result cannot, unless an exception applies. Ask candidates who test positive whether they hold a valid Missouri patient card before you decide.

Why does a written drug policy matter for Missouri workers' compensation?

RSMo 287.120.6 ties benefit reductions to the employer's policy. Where an employee fails to obey "any rule or policy adopted by the employer relating to a drug-free workplace or the use of alcohol or nonprescribed controlled drugs in the workplace," compensation is reduced 50% if the injury was sustained in conjunction with that use, and forfeited if the use was the proximate cause. Refusing a test forfeits benefits if the employer had sufficient cause to suspect use or "the employer's policy clearly authorizes post-injury testing." That is not a hiring rule, but it is a reason to have the policy in place, and handed to new hires, before the first day of work.

Which federal rules still apply in Missouri?

• DOT-regulated roles follow 49 CFR Part 40; a commercial driver needs a verified negative pre-employment result before the first safety-sensitive function (49 CFR 382.301). Under 49 CFR 40.151(e), a state medical recommendation does not turn a positive into a negative. A DOT driver role is also the kind of safety position section 1.7(15) carves out.
• Rescheduling. The April 28, 2026 order moved FDA-approved and state-medical-license marijuana to Schedule III; it does not cover Missouri's adult-use sales. DOT's Part 40 guidance (May 15, 2026) says a Missouri patient card still cannot make a DOT positive negative.
• Federal contractors and grantees need the policy statement and awareness program in the FAR Drug-Free Workplace clause. Where hiring a cardholder would cost a federal monetary or licensing-related benefit, section 1.7(15) does not apply.
• The ADA: see pre-employment medical exams under the ADA.

What should staffing agencies placing workers in Missouri do?

• Do not pass a client's "no THC" rule through blindly. Section 1.7(15) binds "an employer," and the agency is usually the employer of record. Rejecting a cardholder for a positive test, for a job outside the exceptions, can expose the agency even if the client asked for it.
• Classify each order. Ask the client in writing whether the position affects safety or job performance in the way section 1.7(15) describes, or has a federal funding or licensing condition, and keep the answer with the order.
• Agree who tests. Put in the contract whose policy applies, who orders the test and who decides on a positive.
• Licensing and onboarding: see Missouri staffing agency licensing and hiring employees in Missouri; for criminal history timing, see Missouri ban-the-box rules.

A checklist before you test a candidate in Missouri

1. Adopt a written drug and alcohol policy and give it to candidates before testing.
2. Mark which positions are safety or performance positions under section 1.7(15), and why.
3. Test after a conditional offer, consistently for the same position.
4. Use a certified laboratory and medical review officer, and confirm positives.
5. Before acting on a THC positive, ask whether the candidate holds a valid patient card.
6. Keep DOT drivers in the federal program.

Start from the pre-employment drug testing policy template, and compare other states in drug testing laws in hiring.