Traveling as a type 1 Diabetic

Take a letter from your doctor telling that you have type 1 diabetes a need x and y supplies. Put everything in your hand luggage.
We've never had any problems, they haven't even asked for the letter, we just say that my son has t1d and they let us through, we can even take water with no problems.

https://www.tsa.gov/blog/2020/11/13/travel-tip-traveling-diabetes

https://www.tsa.gov/travel/security-screening/whatcanibring/items/insulin

You don't need a letter from your doctor, it won't do anything. They are too easy to fake.
The best thing is to have your prescription labels from the pharmacy. That will include your name, your address, your doctor's name.
This is much more official than a letter.

I travel with a couple of vials of insulin and an insulin pump. My wife travels with a bag full of prescriptions--3 of which are controlled substances in the U.S.

Nobody has ever questioned us about any medications. Last thing they want to do is go through a bunch of bottles trying to figure out what the pills are.

And airlines and the TSA don't care about much of anything--as long as the bottles are 4 oz. or less.

Vandrabrud, prescriptions don't work the same everywhere in the world. Maybe in the us it would work, but here it would be a piece of paper, or just a barcode... I love in Italy and what is usual at least in the UE is a letter from the doctor

I travel with syringes for my arthritis medication. It also needs to be kept cold. At Heathrow in August 2022 security asked to see my prescriptions and the letter from my rheumatologist that explained why I had syringes in a medication cooler. They scrutinised both thoroughly.

I was coming on here to say the Heathrow is an absolute nightmare for taking medical supplies through. They want to check everything and you need to be prepared to argue with them as they asked my friend to open sterile packages and dispose of essential items. If you aren’t flying through the U.K. I don’t think you will have these problems.

A prescription label has the following information: Patient's name, diagnosis, doctor's name , pharmacy where it was dispensed, date it was dispensed, expiration. Not all labels will have diagnosis, but you can request the physician to include it. It is much more official than a letter. I know/have known literally thousands of people with diabetes and this is the advice they get from me. Not one of them has had a bit of trouble traveling internationally or domestically.

Here is the information from gov.uk
**You’re allowed to carry the following in your hand luggage:
essential medicines of more than 100ml, including liquid dietary foodstuffs and inhalers
medical equipment, if it’s essential for your journey
You’ll need to carry proof that the medication is prescribed to you (for example a letter from your doctor *or a copy of your prescription) if it’s both:
in liquid form
in a container larger than 100ml
You do not need to show proof if the medication is either
in tablet form
liquid in a container that’s 100ml or smaller*****

In my opinion a letter will just give them something else to scrutinize. A pharmacy label gives all needed information.
But of course, follow your own counsel (if it is well informed).