I'm Type2 but travel quite a lot so some suggestions would be:
Write a list of your required medications for travel (for yourself
)
If you forget everything else you need: money, ticket, passport and medications (mobile if you must
). The rest can be sorted if you forget it! Make sure you fill in emergency contact in your passport. Have a photocopy of your passport (or picture on mobile etc), leave a copy with your family (in case of loss while away).
Get a small pocket bag for your medications (clear is useful) for hand luggage.
Have a copy of your regular medication prescription, this is useful for security but also if your medications run out/ get lost/stolen while you are away.
Keep medications in original medication packaging if possible (or just have the information leaflet if not).
Carry in your hand luggage enough to get you through a few days (as much as possible really). Certainly more than travel duration time in case of delays or lost luggage (see below).
Put additional medication in your check in luggage (the one that you get separated from, sometimes for longer than you thought), check however that medications can withstand temperature changes.
Always take supplies for longer than your planned trip, delays happen, life happens.
Take teabags (but that might just be me).
Don't know if you need a letter from your doctor (I haven't, but not type 1) but it can't hurt.
Get travel insurance.
To manage separation anxieties agree a specific time in advance to contact your family.
Sort out mobile connections in advance if possible, most accommodation provides free wifi but it's not always reliable.
Airport security people are highly trained and professional but some are less experienced than others. They will have been trained to expect travellers with medications and should be able to deal with this very easily. That said, security can be a bit stressful for everyone involved so go through with a teacher directly behind you who can assist if confusion occurs.
Have a lovely time, Iceland is awesome. There's a place you can visit where you can place one hand on the american continent and one on the european continent, at the same time! Whales! Icelandic people are really friendly and have a great (if sometimes odd, sense of humour). Fish and chips.........