Do I need to explain my illness?

No. You're not required to share medical details with your employer in an email. "I'm unwell and taking a sick day" is sufficient; save documentation for HR if your policy requires it.

Should I email or message on Slack/Teams?

Follow your team's norm, but email creates a record — useful for HR and payroll. Many people do both: a quick chat message for speed, an email for the record.

What if I'm too sick to write anything?

Two sentences are enough: "I'm too unwell to work today. Will update you tomorrow." Nobody expects eloquence from someone with a fever.

Sick Day Email Examples: What to Send Your Boss

A sick day email should be short, sent early, and clear about coverage. You don't need to share medical details — "I'm unwell" is enough. Say whether you're reachable, flag anything urgent on your plate, and give a rough return estimate if you can. Here are 10 examples covering the most common situations.

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Same-day sick notice

Standard sick day

Subject: Sick today — [Your name]

Hi [Manager],

I'm feeling unwell this morning and won't be able to work today. I'll check messages occasionally for anything urgent, but otherwise plan to be back tomorrow.

Nothing on my calendar today except [meeting] — I've asked [colleague] to cover / it can move to [day].

Thanks,
[Your name]

Very short version

Subject: Out sick today

Hi [Manager],

I'm not well today and need to take a sick day. I expect to be back tomorrow and will make sure nothing urgent slips — [colleague] can reach me if anything critical comes up.

Thanks for understanding,
[Your name]

Migraine / can't look at screens

Subject: Sick day — offline today

Hi [Manager],

I've woken up with a severe migraine and won't be able to look at a screen today, so I'll be fully offline. If anything urgent comes up, [colleague] has context on [project].

I expect to be back online tomorrow morning.

Thanks,
[Your name]

Multi-day and uncertain illness

Likely out a few days

Subject: Sick leave — likely out through [day]

Hi [Manager],

I've come down with [flu/a virus] and expect to need a few days to recover — realistically through [day]. I'll confirm as soon as I know more.

Handover notes: [task 1] is with [colleague]; [task 2] can wait until I'm back; the [deadline] may need a short extension.

Thanks,
[Your name]

Extending sick leave

Subject: Re: Sick leave — one more day

Hi [Manager],

I'd hoped to be back today but I'm not recovered yet, so I need one more day. Everything urgent is covered per my earlier note, and I'll be reachable for true emergencies.

Planning to return [day]. Thanks for your patience.

[Your name]

With a doctor's note (formal workplaces)

Subject: Sick leave notification — [dates]

Dear [Manager],

I'm writing to inform you that I'm unwell and, on my doctor's advice, will be on sick leave from [date] to [date]. I've attached the medical certificate for HR.

I've briefed [colleague] on my active tasks and will address anything outstanding on my return.

Kind regards,
[Your name]

Appointments and partial days

Doctor appointment mid-day

Subject: Out for appointment [time]–[time] today

Hi [Manager],

A reminder that I have a medical appointment today from [time] to [time]. I'll be online before and after, and I've kept my calendar clear during that window.

Thanks,
[Your name]

Unwell but able to work from home

Subject: Working from home today — under the weather

Hi [Manager],

I'm feeling under the weather but well enough to work, so I'll work from home today to avoid spreading anything. I'll be on all meetings remotely.

If I fade later in the day, I'll let you know and log off.

Thanks,
[Your name]

Leaving early, feeling worse

Subject: Heading out early — not feeling well

Hi [Manager],

I've been feeling worse as the day's gone on, so I'm going to log off early and rest. My remaining task today ([task]) will be done first thing tomorrow, or [colleague] can pick it up if it's urgent.

Thanks,
[Your name]

Caring for someone else

Sick child

Subject: Out today — sick child

Hi [Manager],

My [son/daughter] is unwell and I need to stay home with [him/her] today. I'll have limited availability but will check messages when I can.

[Meeting] can be moved or [colleague] can run it. I expect to be back tomorrow.

Thanks for understanding,
[Your name]

Quick tips

Send it as early as possible — before your workday starts, ideally.
You don't owe anyone a diagnosis. "I'm unwell" is a complete explanation.
Always mention coverage: what's urgent, who can handle it, what can wait.
Say whether you're reachable. "Fully offline" is a legitimate answer.
Follow your company's policy — some require HR notification or a doctor's note after 2–3 days.

Frequently asked questions

Do I need to explain my illness?: No. You're not required to share medical details with your employer in an email. "I'm unwell and taking a sick day" is sufficient; save documentation for HR if your policy requires it.
Should I email or message on Slack/Teams?: Follow your team's norm, but email creates a record — useful for HR and payroll. Many people do both: a quick chat message for speed, an email for the record.
What if I'm too sick to write anything?: Two sentences are enough: "I'm too unwell to work today. Will update you tomorrow." Nobody expects eloquence from someone with a fever.

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