You have more legal protection than you might think — and more choice
about how much to disclose than most people realize.
What the law actually says (U.S.)
FMLA (if your employer has 50+ employees and you've worked
there long enough to qualify) entitles you to up to 12 weeks of unpaid,
job-protected leave for a serious health condition — including treatment for
substance use disorder — without disclosing the specific diagnosis, only that
it's a medical condition requiring treatment.
The ADA protects people who are in treatment or recovery,
or who have completed treatment, from discrimination — but it does not
protect someone who is currently using illegal drugs. Being in a supervised
treatment program (including MAT) counts as protected status.
You are generally not required to disclose a specific diagnosis to get
medical leave — "a medical condition requiring treatment" is usually enough
for FMLA paperwork, filled out by your provider, not by you explaining it
directly to your employer.
Something like
"I wanted to let you know I'm starting treatment for opioid
use disorder. I'm telling you because I trust you, and because I may need some
flexibility with my schedule for appointments. I'm not asking for anything
special beyond that right now."
Something like
"I need to take some medical leave for ongoing treatment.
I'd rather keep the details private, but wanted to give you a heads-up and
submit the FMLA paperwork through HR."
Something like
"I need to request [X days] of leave / a schedule
adjustment for a medical appointment. I can provide documentation through HR
if needed, but I'd prefer to keep the specifics between me and my doctor."
Whichever route you choose, medical leave paperwork usually goes through HR
or a leave administrator, not your direct manager — that's a real option if
privacy from your day-to-day supervisor matters to you.