Yeah I'd go to the docs to get it checked, but it may just be because it is.
I've always had a high pulse rate, so whilst having a drink at the pub my fitbit thinks I'm exercising
cos mine is often about 85-105 whilst sitting down (currently 86) - I think its slowing down very gradually over the years - I remember once at school we did pulse rates in class and my idle pulse was the highest in the class by a fair old way at 114.
And yes I've had T1 since I was young, but my mother and grandmother also have/had high pulse rates and they are/were not diabetic, so I suspect for me its just hereditary down my mums side of the family.
I did have a 24-hour test done and they were happy as mine drops down to about 65-75 overnight so it does calm down slightly.