Do I have to tell my employer about my prescription?
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Usually yes — if your drug and alcohol policy requires disclosure of medication that could affect safe work, and it almost certainly does. How you disclose matters as much as whether you do.
What the policy can require
Employers can lawfully require workers — especially in safety-relevant roles — to disclose any medication that may affect their ability to work safely. That includes prescribed medicinal cannabis, and particularly anything containing THC. What they generally cannot demand is your full medical history or direct contact with your doctor without consent: a prescription is sensitive health information, and collection should be limited to what the safety purpose requires.
The disclosure mistakes from the case law
- Saying nothing and hoping the random test never lands on you (Gauci).
- Disclosing the cannabis but not the THC (Mills) — treated as a breach, not a technicality.
- Disclosing once, then changing or resuming without updating anyone (Haigh). Every prescription change re-triggers the duty.
- Disclosing verbally with no record. If it is not in writing, you may be arguing about what was said at the worst possible moment.
How to disclose well
- Re-read your D&A policy first — note exactly what it requires and to whom.
- Disclose in writing: the medication class, that it contains THC (if it does), and that you want to work through fitness-for-work implications cooperatively.
- Attach or offer a letter from your prescriber addressing fitness for your specific duties and dosing timing relative to shifts — the Rights Kit includes the question list to take to that appointment.
- Keep copies of everything, and update the disclosure whenever the prescription changes.
“But it’s private medical information”
Both things are true: your health information deserves privacy protection, and a policy can validly require safety-relevant disclosure. In the decided cases, privacy instincts that led to silence cost people their jobs, while the privacy protections that actually held up were about limiting what was collected and who saw it — not about whether to disclose at all.