Morning, I haven’t been feeling well since last night. I would therefore request you to please grant me sick leave. Thank you!
Morning, I am suffering from fever since last night, so I am not able to come to the office today. Please grant me a leave for one day.
Diarrhea is troubling me since morning, so I wouldn’t be able to report to work today.
另外，仲有 Feel under the weather 意思係身體不適，通常係日常傾計會用到～屬於非正式英語，所以係唔會用係商業書信或正式書信當中。
例如：I’m feeling a bit under the weather – I think I’ve got a slight fever.