Formal warning at work

Hi everyone

I’m after some advice, I received an email today from HR inviting me to an absence review meeting next week due to the amount of sickness I’ve had lately.

I have crohns and a stoma bag. My employer knows this and has done before I started at the company 3 years ago.

I have roughly 1 or 2 days off sick every month due to my bag leaking or just being in pain

How am I best to handle this? What’s my rights