How long to give lecturer to reply to email?

[academias]

I graduated a year ago and recently emailed my undergraduate dissertation supervisor to ask if she would be able to be one of my academic references for some applications.

I emailed last week to ask this which was four weeks before the deadline. It has been exactly a week and I have not yet had a reply and now that puts it at three weeks before the application deadline.

This lecturer is the one who knows me best academically as they were my supervisor, work in the area I am hoping to go into and they taught me during all the relevant modules. However they are also very senior and very busy so I was anticipating there would be a delay in their response and I completely understand.

When would it be polite to send a reminder? Should I just forward the original email or write a new one?

Oh that’s fantastic! So was that for the initial phd application or for another one? I will keep my fingers crossed that you get a place.

@Pota2 It was for a different PhD. It's in a really interesting area of research and aligns closely with my research interests so I hope my enthusiasm comes across in my application. Thank you for all of your support in this thread, I really appreciate it. :)