Hi Sarazk
Your diabetes has nothing to do with friends/no friends.Make sure you look after yourself.
Are there any activities/groups at or after school you can join/participate in for example Duke Of Edinburgh Awards,sport classes.There'll be loads of activities and classes outside of school too eg check what clubs/activities etc you can join advertised at your local community centre or library etc etc etc.Volunteer at a local branch of Red Cross,your local wildlife parks the list goes on.My daughter goes along to Beavers/Brownies/Cubs each week and has made a number of friends nearby as a result.
My son used to go to Boys Brigade,photography clubs.
I did Duke of Edinburgh and helped at local mentally handicapped club as part of it when i was younger,did First Aid for the Red Cross (they train you for free) at Newcastles Telewest Arena made friends saw dozens of gigs and bands for free as well as sporting events etc etc.
I'm sure you'll find a few you like to do and make friends during meets and socially outside of meets.