Hello,
For further context, I have medical issues that may need me to leave work for ~3 hours from time to time (maybe once every 2-3 months), in order to go to the clinic and see the specialist. For these things, it's almost impossible to predict when it will happen as well.
While I am offering to work on the weekend to offset the time lost, and I also say I'll work late to finish the tasks, I can't help but feel bad for leaving.
I should also preface that I'm not a star performer by any means and I'm close to a PIP. Would my manager be annoyed?