What to do when you get sick in your first 90 days

Getting sick in your first ninety days feels higher-stakes than it is.

You’re new. You don’t know the norms yet. You worry that taking a day will register as “first-year who can’t hack it.” So you half-work through the fever, send a couple of replies that don’t quite make sense, and everyone comes away mildly worried about you.

Don’t do that. Sick days are normal. Managers expect them. The only thing that goes wrong in your first ninety days is not the sick day — it’s how some new hires handle it.

The morning-of message

Send it early. Before the day starts, not two hours into the morning. Keep it short. Give your manager three things and nothing else.

Hey [Manager] —
Woke up with a bad cold / stomach bug / etc. Going to take today
to rest. I'll check messages briefly mid-morning to flag anything
urgent, but I'll be offline otherwise. If anyone needs X today,
Sarah has the context.
Back tomorrow (or will update you in the morning if I'm not).

What’s in there:

1. What’s wrong, one phrase. Cold, stomach bug, migraine, injury. “Not feeling well” is vague enough to sound fishy. “Cold” is honest and specific enough that nobody wonders.
2. The plan. “Taking today to rest” is a plan. “I might try to work a little” is not a plan and worries your manager.
3. Coverage. If something concrete needed you today, name the backup. Shows judgment.
4. When to expect you back. Default to tomorrow. If you’ll need more, say so now — don’t stretch one-day-at-a-time.

Send it. Then stop managing the office.

The thing to absolutely not do

Don’t try to work sick from home unless you genuinely have to and can actually function. The output you produce with a fever is unreliable. The emails you send are worse than the emails you’d send not sick. The Slack messages you type half-conscious are the ones coworkers remember awkwardly for a year.

Your manager would rather you take a real day than send low-quality output pretending everything is fine. “I worked through it” is not the badge you think it is in your first year. “I took the day, came back clear-headed Wednesday, and shipped the thing” is a better story.

How many days is normal

In most US corporate jobs:

• One honest day, clear message, clear-headed return: normal. Nothing to explain.
• Two or three days for a cold or flu, with clear comms: normal.
• A week+ without clear communication: concerning. If you’ll be out more than three days, tell your manager on day two, not day five.
• Frequent single-day absences without a pattern: can look avoidant. If you’re chronically dealing with something, it’s worth a one-time conversation framed as “I’ve had a few rough weeks with allergies / migraines / etc., didn’t want you wondering.”

Don’t try to hide a recurring issue by camouflaging it as one-off days. Managers notice the pattern eventually, and it’s worse when they’ve noticed without you naming it.

What to do while you’re out

Rest.

If you’re really bored: nothing. Watch TV. Sleep. Do not answer Slacks, do not “just quickly send this email,” do not check in halfway through the day to prove you’re virtuous. The day off is the product.

One exception: if something blows up that genuinely only you can unblock — a client escalation, a deploy gone wrong — triage briefly, hand it to someone, return to rest. Don’t try to fully handle it.

The return-to-work message

The day you come back, low-key:

Hey [Manager] — back today. Caught up on the most urgent threads.
Picking up X and Y first; Z slid to later this week — I'll shift
the timeline in the doc. Let me know if priorities moved while I
was out.

Three lines. You’re oriented, you’re picking up the work, and you’ve proactively flagged the one thing that slipped. That last piece is the move most people skip. Acknowledging the slip upfront saves your manager from having to ask.

Do not apologize profusely. “I’m so sorry for being out, I really feel terrible about it” makes your manager feel weird. You were sick. You took a sick day. You’re back. A short, oriented message is what they want.

What your manager is actually thinking

Most managers react to first-year sick days in one of three ways:

• “Thanks, feel better.” That’s 85% of the time.
• “Is everything okay?” When they’re being genuinely kind. Not a trap.
• “Huh, that’s two sick days in three weeks.” When there’s a pattern. If you see this, it’s time for the “by the way, here’s what’s going on” conversation.

Very few managers secretly judge first-year sick days harshly. The ones who do are the same managers who’ll find something else to judge harshly, and there’s no game you can play that makes it better.

—

I’ve watched first-years burn three days of credibility by trying to push through illness instead of taking the one day. The math is bleak: you produce 40% of your usual output, look 80% as competent, and use 100% of the energy. The sick day is the strictly dominant strategy. Take it.

For the first-week rhythm that builds enough credit that a day off doesn’t feel costly, see the Week 1 Checklist. For the broader first-90-days system, see the First 90 Days OS.