With regret, I have to claim ESA and PIP due to multiple health issues including T1 and find the system very frustrating. I'm probably teaching you to suck eggs, but...
When filling out your application, or appeal, look at the grading descriptors (
https://www.sense.org.uk/content/esa-descriptors-determine-whether-you-have-limited-capability-work) and think about your worst days. You need to evidence the challenges you face, and having hypos and hypers isn't usually enough, it's the way they affect your life.
Think about if you've ever been so low you've become unconscious, do you need help to treat a hypo, do you have hypo awareness, do the dizzy spells prevent you from leading a normal life? That sort of thing. Does the eye condition cause you to avoid certain activities? Have you a precedent where you're prone to DKA? Any neuropathic issues? What effects does having these issues have on your state of mind? Do you get anxious leaving the house or driving / using piblic transport 'just in case'? That side is important too.
The main thing is to provide clear and concise evidence - don't be stoic, be honest about how it affects you. Diabetes alone as a condition rarely qualifies - it's how your life is impacted by it and what you can/can't do because of your conditions that is assessed.