Subject: [Short description of your excuse, e.g. “Not feeling well,” “Coming down with a cold”] Hi [supervisor’s name], I woke up feeling under the weather today, and I think I’m coming down with [name of a short, believable illness, like a cold, sore throat, stomach bug]. I’m feeling pretty badly and don’t want to risk infecting anyone else, so I don’t think I’ll be able to make it into work today. I’m sorry for the inconvenience—I know how busy we are, so I’ll do my best to rest up today and get back in tomorrow morning. I’ll be on email, so if there’s anything I can do from home in the meantime, please let me know! Thanks for understanding. Best, [Your name]