Previously this was not automatic. A submission had to be sent to the CRA to prove that the disability was life interrupting, the same as for Autism and other conditions. I had heard instances of folks with Type 1 Diabetes, who had an insulin pump being denied a Disability Tax Credit by the CRA. I have no direct knowledge of this, but it didn’t surprise me.
When Bill C-19 (the 2022 Federal Budget Law) passes, this should be part of how things work going forward. This seems to only be for Type 1 Diabetes.
This is all heavily cribbed from the following Facebook Post. Add that resource to your Facebook if you are dealing with Diabetes.
 Bill C-19: An Act to implement certain provisions of the budget tabled in Parliament on April 7, 2022 and other measures (first reading) https://parl.ca/DocumentV…/en/44-1/bill/C-19/first-reading