In AmE "medical leave" is a lengthier process. In your case, I would call it "a sick day".
Student or Learner
.it is correct the sentence below?
Hi boss, just let to u know...I am on Medical leave today as feeling not well. Headache and sore throat already...
Just inform you, I am on medical leave today. Had high fever.
A better version...
Just inform you, i am on sick leave today. I am feeling a bit feverish. Tq
Does my suggestion make sense to you?
Many companies do not accept sick leave notifications by email - they want to speak to the person themselves so they expect you to phone in. I am lucky that my boss accepts text message notifications. I usually send:
"Morning [boss's name]. I'm really sorry but I won't make it in to work today. I have a high temperature and a really bad headache. Hopefully I'll be back tomorrow but I'll confirm that with you later. Thanks. [My name]"
That would work by email too.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.