Subcontractors · Best Practice · Pre-Construction

Drug and Alcohol Policy Agreement

An agreement signed by workers acknowledging the site drug and alcohol policy and consenting to random testing.

Last reviewed: 29 March 2026 — This guide reflects UK law as of this date. MHSWR 1999 remains current with no amendments enacted as of 29 March 2026. Next scheduled review: 29 March 2027.

Legal basis	MHSWR 1999 + HSWA 1974
Why a signed agreement	For drug testing to be lawful, the policy must be communicated in advance and workers must be aware they may be tested. The signed agreement provides documented evidence.
Policy requirements	What substances are covered; when testing occurs (induction, random, post-incident, reasonable cause); consequences of positive test; support available.
Prescribed medications	Workers taking medications that may impair safety must declare this.
Testing legality	Lawful where policy is communicated, testing is consistent and non-discriminatory, GDPR compliant.

1. Drug & Alcohol Policy Agreement — Informed Consent to a Safety Requirement

The agreement is the documented acknowledgement that each worker has been informed of the site's policy before accessing the site. It provides the legal foundation for the testing regime. Without prior communication, random testing may be legally challengeable.

The policy agreement should be signed at site induction — it forms part of the induction process

2. Drug & Alcohol Policy Agreement — Content

The following table sets out the sections that a well-structured drug and alcohol policy agreement should include.

Section	What to include
Policy statement	Zero tolerance statement covering all site activities.
What is covered	Illegal drugs, alcohol, impairing substances including legal highs and solvents.
Testing	Induction, random, post-incident, reasonable suspicion. Refusal to submit to testing treated as a positive result.
Prescribed medications	Workers must inform their supervisor of any medication that may impair their ability to work safely.
Consequences	Immediate removal from site. Employer notified. Potential disciplinary action by employer.
Support available	Employee Assistance Programme (EAP) details and/or occupational health referral pathways.
Worker acknowledgement	Signature confirming the worker has read, understood, and agrees to comply. Date of signing.

3. Common Mistakes

Not communicating the policy before testing

Testing without prior communication of the policy may be legally challengeable. The signed agreement is the evidence that communication took place.

Not applying consistently across all workers

Testing must be applied consistently regardless of role, seniority, or employer. Selective application creates discrimination risk.

Not including prescribed medication obligations

Prescription medications can impair safety. The policy must require workers to declare medications that may affect their ability to work safely.

Not including information about support for dependency issues

A policy that only addresses consequences without offering support pathways is incomplete. Include EAP and occupational health referral details.

Using positive test results as automatic termination without proper process

A positive test should trigger removal from site and notification to the employer. Employment decisions are for the worker's employer to make following their own disciplinary procedures.

4. Frequently Asked Questions

Is drug testing lawful on UK construction sites?▾

Yes — where a policy has been communicated and workers have agreed. Testing must be non-discriminatory, use competent testing methods, and be GDPR-compliant.

Can workers be tested without specific cause?▾

Random testing is lawful where it is specified in the signed policy agreement. The agreement provides the documented basis for unannounced testing.

What type of test is typically used?▾

Oral fluid (saliva) testing using lateral flow immunoassay. Results are available in 5–10 minutes. Positive results should be confirmed by laboratory analysis.

How should the PC handle a positive test?▾

Immediate safe removal from site. Inform the worker’s employer. Retain documentation. Employment decisions are for the worker’s employer to make, not the PC.

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