Introduction
He's good. Better than most people there. And you know, because you've seen it, or he told you, or the evidence has accumulated past the point where you can pretend otherwise.
Reporting could end his career over something that appears to be harming nobody. Not reporting could make you complicit in something you haven't imagined yet.
Start With the Only Question That Matters
Is anyone at risk of physical harm?
If he operates a vehicle, machinery, or aircraft. If he is a surgeon, a nurse, a pilot, an electrician, a driver, a pharmacist. If he handles medication, or has responsibility for children or vulnerable people. If a lapse in his judgment could injure someone.
Then this is not a question about loyalty. His competence is not the relevant variable, because competence is precisely what impairment removes, unpredictably, on a day nobody can identify in advance. The performance you've observed is a description of the days that went fine.
Report it. Through whatever formal channel exists. The discomfort of doing so is not comparable to the alternative.
If Nobody Is at Risk
Then the question is genuinely different, and the answer is much less obvious.
An accountant using cocaine at weekends. A designer who drinks heavily at home. A colleague whose private life has entered your awareness and would horrify HR.
Here, "should I report" is not a safety question. It's a question about surveillance, about what your employer's interest in a person's private conduct actually amounts to, and about what reporting would achieve.
"He Does His Job Really Well" Is the Wrong Measure
Worth pressing on the premise in your question.
Performance at work is a poor detector of addiction. It measures whether someone can maintain a visible surface, which is a skill, and one that heavy use is compatible with for a long time. The clinical picture of a substance use disorder concerns loss of control, escalation, and continued use despite consequences — almost none of which appears in a performance review.
And functioning that depends on nothing going wrong is not stability. The margin quietly shrinks. The colleague who is excellent this year is frequently excellent right up until an ordinary bad week arrives and there is nothing left to absorb it.
So "he's good at his job" tells you less than it feels like it does. It does not tell you he is fine, and it does not tell you the risk is zero — it tells you the bill has not arrived yet.
What Reporting Would Actually Do
Be concrete rather than abstract.
In most workplaces, a report of drug use leads to termination or to a testing regime, not to treatment. The employee assistance programs that could help are typically accessed by the employee voluntarily, not by being turned in.
So the likely outcome is that he loses his job, loses his insurance, loses the structure that has been holding his life together, and enters unemployment with an addiction and less to lose. That sequence does not tend to produce recovery.
You would have removed a functioning man's functioning. Whether that helps him is at best unclear.
The Third Option Nobody Mentions
You are not choosing between reporting and doing nothing.
You can talk to him.
Not a confrontation — the evidence is clear that staged confrontations underperform. Something smaller. I noticed. I'm not going to tell anyone. I'm worried about you, and if you ever want to talk about it, I'm here.
That sentence costs you very little. It occasionally changes something. And it leaves you the person he can come to, which is worth more than a report to HR ever will be.
Where That Falls Apart
If his use is escalating and safety becomes relevant. If he asks you to cover for him — and he probably will, eventually. If the arrangement quietly makes you a participant.
Covering is the line. The moment you are lying for someone, you have taken on their risk and their consequences, and you have removed one of the pressures that might otherwise have prompted them to act.
You can decline to report and also decline to protect. I'm not going to tell anyone, and I'm also not going to lie for you.
Check Your Own Motives
Uncomfortable and necessary.
Do you like him? Would you report him if you did? Is there a promotion involved, or a history, or a grudge?
Reports made from resentment tend to be dressed in the language of responsibility, and everyone involved can usually tell.
Know the Rules That Bind You
Some of this isn't yours to decide.
Certain roles carry a legal or professional duty to report impairment — healthcare, aviation, transport, childcare. Some employment contracts require it. Some licensing boards impose it on colleagues.
If you have such an obligation, the ethical question above is largely moot, and failing to act may expose you as well. Find out what applies to you rather than reasoning from first principles about a situation that has already been decided by regulation.
The Confidentiality He Might Have
One thing worth knowing, if he's considering getting help.
If he seeks treatment voluntarily, his records may carry protections. Many employers treat a person who discloses and seeks help very differently from one who is discovered. That is the path you can point him toward, and it is far more likely to end well than the path that begins with your report.
The Bottom Line
If anyone could be physically harmed, report it — his competence describes the days that went fine, not the day that won't. If nobody is at risk, notice that reporting usually produces termination rather than treatment, and that you have a third option: tell him you know, that you won't say anything, and that you won't lie for him either. Check whether a legal duty already decides this. And check what you actually feel about him.