Agree with the above advice. Take a trade union rep (preferably a full time TU officer) with you to any meeting. If that's not possible, take a friend or more experienced colleague who can help and support you.
A few things for you to think about:
- are you sure it's a disciplinary meeting? What did the letter say? It might be simply an absence review.
- do they know that you are diabetic? and/or that you will need to go for review on your eyes every 6 months? Is that review diabetes related, or something separate? Will you need time off to atend those reviews? Take any GP or Consultant appt. letters with you to the meeting.
- did you explain the reasons for your absences each time? Were the absences diabetes-related or not?
- for how long were you absent on each occasion?
- is it a large or a small company? How many other staff are there? Are they able to cover your absence if it is at short notice? How much disruption is caused when you (or anyone else) are absent?
- do you have a copy of the company sickness absence policy? Occupational Health? Any other employment policies? Were you given these when you joined them last November? Re-read your employment contract; what does it say about attendance and/or absence?
- keep calm and explain what happened to cause your sickness, (if you know) as simply as you can, and what you did about it; try not to be defensive,or aggressive. Write it down, if you need to, to help keep your mind clear and focussed. It's ok to go into any meeting with your own notes.
- talk it through with your trade union rep, so that you fully understand what the meeting is about, what the format will be, what is likely to happen, and what happens afterwards.