You don’t need a elaborate excuse or a long explanation. A brief, professional message sent before your shift starts is enough to take a last-minute mental health day at most workplaces. The key is keeping it simple, covering your responsibilities, and saying only what you need to say.
What You Actually Need to Tell Your Employer
You are not legally required to disclose a specific diagnosis or explain why you feel unwell. Under most sick leave policies, “I’m not feeling well” is a complete reason. Mental health is health, and a sick day covers it the same way it covers a migraine or a stomach bug.
If your leave might qualify for protection under the Family and Medical Leave Act, you do need to provide enough information for your employer to recognize the situation could be FMLA-eligible. But for a single sick day, that level of detail is rarely necessary. You don’t need to say the words “mental health,” “anxiety,” or “burnout” unless you want to. A general statement that you’re unwell is sufficient.
The Americans with Disabilities Act also offers protections worth knowing about. Employers with 15 or more employees are required to provide reasonable accommodations for disabilities, including mental health conditions. That can include modifying leave policies or granting unpaid leave even when you’ve used up your standard allotment. If you’re dealing with an ongoing mental health condition and need time off periodically, that’s a conversation worth having with HR separately from your immediate sick day request.
How to Send the Message
Use whatever method your workplace normally expects for calling out. If people typically send a Slack message or email to their manager, do that. If your team calls, call. Following the standard process matters more than the specific words you use, because it shows respect for the system even on short notice.
Send it as early as possible. Before your workday starts is ideal, even if that means sending a message at 6 a.m. that your boss won’t read until 8. The timestamp shows you gave as much notice as you could.
Keep it to three or four sentences. Here’s what to include:
- The fact that you won’t be in. State it directly: “I’m not feeling well and need to take a sick day today.”
- Whether you’ll be reachable. If you need to be fully offline (and you should be, if you’re taking this day to recover), say so.
- A coverage plan. Name a colleague who can handle urgent questions, or note where key files and projects stand.
- When you expect to return. “I plan to be back tomorrow” is enough.
Example Messages You Can Adapt
If you want something short and low-detail:
“I’m not feeling well today and will need to take a sick day. I’ll be offline to rest. For anything urgent, [colleague’s name] can help. I expect to be back tomorrow.”
If you want to show you’ve thought about your team’s workload:
“Unfortunately, I woke up feeling unwell and need to take a sick day today. I apologize for the short notice. I’ve updated [colleague’s name] on where things stand, and my draft for [project] is saved in our shared folder. I plan to be back tomorrow and will let you know if anything changes.”
If your workplace culture is more formal:
“Please accept this as notification that I’ll be taking sick leave today. I will be fully offline for the day. For urgent matters, [colleague’s name] has been briefed and can serve as the point of contact. I expect to return tomorrow.”
Notice that none of these messages mention mental health specifically. They don’t need to. They’re professional, brief, and focused on minimizing disruption for the team.
What Not to Do
Don’t over-explain. The more details you volunteer, the more questions you invite. “I’m not feeling well” doesn’t require a follow-up. “I’ve been having trouble sleeping and my anxiety has been really bad and I just can’t focus” opens the door to a conversation you probably don’t want to have over text with your manager at 7 a.m.
Don’t apologize excessively. One brief “sorry for the short notice” is fine. Repeating it multiple times signals guilt, which can make a routine sick day feel like a bigger deal than it is. You’re using a benefit you’ve earned.
Don’t ask permission if your workplace treats sick days as a notification rather than a request. There’s a meaningful difference between “Would it be okay if I took today off?” and “I won’t be in today.” Read the room based on your company culture, but in most cases, you’re informing your manager, not negotiating.
Don’t check your email or Slack “just once.” If you told your team you’d be offline, be offline. Partially disconnecting defeats the purpose. The point of a mental health day is actual recovery, not performing wellness while still monitoring your inbox.
If You’re Worried About How It Looks
A single last-minute sick day is normal. Every employee does it eventually. Your manager has done it. What makes the difference isn’t whether you take the day, it’s whether you handle it professionally. Giving early notice, naming a backup, and returning the next day as planned all signal reliability.
If you find yourself needing mental health days frequently, that’s worth paying attention to, not because it looks bad to your employer, but because it may point to something that needs more sustained support than a day off can provide. Recurring burnout, chronic anxiety, or depression often benefit from ongoing treatment rather than occasional rest days.
For people with a diagnosed mental health condition, the ADA requires covered employers to engage in what’s called an “interactive process” to find reasonable accommodations. That could mean a flexible schedule, periodic mental health leave, or modified duties during difficult periods. Your employer can’t require you to be “100% healed” before returning to work if you can do your job with or without accommodations. That’s a legal protection worth knowing about if your mental health needs extend beyond the occasional sick day.
Making the Day Count
Once you’ve sent the message, put your phone somewhere you won’t see work notifications. The anxiety of wondering whether your boss is annoyed will undermine the whole point of the day.
A mental health day works best when you treat it with the same seriousness as recovering from a physical illness. That means rest, not errands. Sleep in, go for a walk, sit outside, do something that genuinely recharges you. Avoid the trap of spending the day doom-scrolling or doing chores you’ve been putting off. Those things feel productive but don’t address the exhaustion that made you need the day in the first place.
Before bed that night, send a brief message confirming you’ll be back the next day. Something like “Feeling much better, see you tomorrow morning” closes the loop cleanly and lets your manager plan accordingly.