Should you tell your employer about your medical cannabis prescription?

This decision splits into four situations, and the answer really depends which one describes your job.

Situation 1: Office role, no drug testing, no safety-critical tasks

You work in an office, on a laptop, at a desk. There is no drug-testing programme and no safety-sensitive element to your role. Your employer has no operational need to know what's in your medicine cabinet.

Default position: don't volunteer. Your prescription is private medical information, protected by data-protection principles and by the ordinary expectation that health details are yours. Disclosing invites questions and creates a record for no gain. If your condition itself needs adjustments (flexible hours, remote work, a quiet space), disclose the condition — often through occupational health — and let the medication conversation follow only if it becomes relevant.

Situation 2: Drug-tested workplace

Testing happens — random, pre-employment, post-incident or all three. This is where the calculation flips.

THC metabolites can show in urine tests for days to weeks after use. Standard workplace testing panels don't distinguish between prescribed and illicit cannabis. A positive result in a testing culture usually goes straight into a disciplinary process; explaining afterwards places the burden on you to reverse an already-established narrative.

Default position: disclose proactively, in writing, through HR or occupational health. Ideally before your first test, and always before an incident. A one-page letter is enough: named condition, prescriber, product, that you take it in accordance with prescribing directions, and a request that your record note this so any positive test is interpreted against your prescription rather than triggering an assumption of misconduct. Ask for written acknowledgement.

This approach also gives you the strongest position under the Equality Act 2010 if the underlying condition is a disability — the employer is on notice, and a subsequent decision that fails to account for the prescription is much harder to defend.

Situation 3: Safety-critical role

Driving for work, operating machinery, working at height, healthcare with prescribing or dispensing responsibilities, aviation, rail — any role governed by a specific safety duty or professional regulator. This category has the least room for discretion.

Regulator rules and role-specific safety policies commonly require disclosure of any medication that could impair performance, whether prescribed or over the counter. A failure to disclose here isn't a data-protection question — it's typically a straightforward breach of contract and often a safety offence.

Default position: disclose, in writing, and expect a formal process. Occupational health will assess your fitness for the specific role. The right conversation is about timing, dose, product formulation, and any adjustments (e.g. never driving within X hours of dose). This is protective for you, not adversarial — a documented process that assessed your fitness before an incident is exactly what you want in your file if the incident ever comes.

Situation 4: New job, in the application or offer stage

Employers can ask limited health questions before making a job offer under section 60 of the Equality Act 2010 — only where relevant to intrinsic requirements of the job, disability-based positive-action, or monitoring. A general "do you take any medications?" question at application stage is usually not permitted.

After a conditional offer, most employers ask a routine health questionnaire. Answer it honestly. If the role includes safety-critical or drug-tested elements, disclosure at this stage is stronger than doing so once you're already in post.

How to actually disclose, if you decide to

A confident disclosure has three properties: it's in writing, it's routed through the right person, and it names what matters.

1. Route it via HR or occupational health, not your line manager. Line managers aren't trained to handle this and often escalate anyway; going through HR from the start controls the audience.
2. Put it in writing. A short letter or email. Keep a copy. Ask for written acknowledgement.
3. Include: named condition (if you're comfortable), the fact of a lawful specialist prescription, product and dose (they don't need the milligrams — "prescribed cannabis-based oil, taken twice daily as directed" is enough), that you take it in line with prescribing directions, and that you are not impaired at work.
4. State what you're asking for. Usually: that the disclosure is placed on file, that any drug-test result is interpreted against your prescription, and that any adjustments or occupational-health assessment be arranged through the normal channel.
5. Don't apologise or over-explain. It's a lawful medicine for a medical condition. Frame it that way.

What if the response is bad

Occasionally an employer reacts poorly — suspension, informal pressure, sudden performance concerns. Don't respond in the moment. Document everything, follow the grievance process, and — early — speak to Acas, a solicitor familiar with disability discrimination, or your union rep. Detriment following disclosure is exactly the pattern discrimination law is built to address.

For the underlying testing rules and what a positive result actually triggers, see the workplace drug testing pillar.